The Optimized Link State Routing Protocol Version 2LIX, Ecole Polytechnique+33 6 6058 9349T.Clausen@computer.orghttp://www.ThomasClausen.org/BAE Systems Advanced Technology CentreWest Hanningfield RoadGreat Baddow, ChelmsfordUnited Kingdom+44 1245 242194chris.dearlove@baesystems.comhttp://www.baesystems.com/Alcatel-Lucent Bell Labs+33 6 7337 1880philippe.jacquet@alcatel-lucent.comFujitsu Laboratories of America1240 E. Arques Ave.SunnyvaleCA94085USAulrich@herberg.namehttp://www.herberg.name/
Routing
Mobile Ad hoc Networking (MANET)
This specification describes version 2 of the Optimized Link State
Routing Protocol (OLSRv2) for Mobile Ad Hoc Networks (MANETs).
The Optimized Link State Routing Protocol version 2 (OLSRv2) is the
successor to OLSR (version 1) as published in . Compared to , OLSRv2 retains the
same basic mechanisms and algorithms, enhanced by the ability to use a link
metric other than hop count in the selection of shortest routes. OLSRv2 also
uses a more flexible and efficient signaling framework and includes some
simplification of the messages being exchanged.
OLSRv2 is developed for Mobile Ad Hoc Networks (MANETs). It operates as a
table-driven, proactive protocol, i.e., it exchanges topology information with
other routers in the network regularly. OLSRv2 is an optimization of the
classic link state routing protocol. Its key concept is that of multipoint
relays (MPRs). Each router selects two sets of MPRs, each being a set of its
neighbor routers that "cover" all of its symmetrically connected 2-hop neighbor
routers. These two sets are "flooding MPRs" and "routing MPRs", which are used to
achieve flooding reduction and topology reduction, respectively.
Flooding reduction is achieved by control traffic being flooded through the
network using hop-by-hop forwarding, but with a router only needing to forward
control traffic that is first received directly from one of the routers that
have selected it as a flooding MPR (its "flooding MPR selectors"). This
mechanism, denoted "MPR flooding", provides an efficient mechanism for
information distribution within the MANET by reducing the number of
transmissions required .
Topology reduction is achieved by assigning a special responsibility to routers
selected as routing MPRs when declaring link state information. A sufficient
requirement for OLSRv2 to provide shortest routes to all destinations is that
routers declare link state information for their routing MPR selectors, if any.
Routers that are not selected as routing MPRs need not send any link state
information. Based on this reduced link state information, routing MPRs are
used as intermediate routers in multi-hop routes.
Thus, the use of MPRs allows reduction of the number and the size of link state
messages and reduction in the amount of link state information maintained in each router.
When possible (in particular if using a hop count metric), the same routers may
be picked as both flooding MPRs and routing MPRs.
A router selects both routing and flooding MPRs from among its one-hop neighbors
connected by "symmetric", i.e., bidirectional, links. Therefore, selecting routes
through routing MPRs avoids the problems associated with data packet transfer over
unidirectional links (e.g., the problem of not getting link-layer acknowledgments
at each hop, for link layers employing this technique).
OLSRv2 uses and extends the MANET Neighborhood Discovery Protocol (NHDP)
defined in and also uses the Generalized MANET Packet/Message Format , the TLVs specified in
and, optionally, message jitter as specified in
. These four other protocols and specifications
were all originally created as part of OLSRv2 but have been specified
separately for wider use.
OLSRv2 makes no assumptions about the underlying link layer. OLSRv2, through
its use of , may use link-layer information and
notifications when available and applicable. In addition, OLSRv2 uses link metrics
that may be derived from link layer or any other information. OLSRv2 does not
specify the physical meaning of link metrics but specifies a means by which new
types of link metrics may be specified in the future but used by OLSRv2 without
modification.
OLSRv2, like OLSR , inherits its concept of forwarding
and relaying from the High Performance Radio Local Area Network (HIPERLAN) (a MAC-layer protocol), which is standardized by ETSI
. This document does
not obsolete , which is left in place for further
experimentation.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
.
All terms introduced in , including "packet",
"Packet Header", "message", "Message Header", "Message Body", "Message Type",
"message sequence number", "hop limit", "hop count", "Address Block",
"TLV Block", "TLV", "Message TLV", "Address Block TLV", "type" (of TLV),
"type extension" (of TLV), "value" (of TLV), "address", "address prefix",
and "address object" are to be interpreted as described there.
All terms introduced in , including "interface",
"MANET interface", "network address", "link", "symmetric link",
"symmetric 1-hop neighbor", "symmetric 2-hop neighbor", "symmetric 1-hop neighborhood"
"constant", "interface parameter", "router parameter", "Information Base",
and "HELLO message" are to be interpreted as described there.
Additionally, this specification uses the following terminology:
A MANET router that implements this protocol.
A MANET interface running this protocol. A router running this protocol MUST
have at least one OLSRv2 interface.
A network address that may be used as the destination of a data packet.
A router that implements this protocol will need to distinguish a routable
address from a non-routable address by direct inspection of the network
address, based on global-scope address allocations by IANA and/or
administrative configuration (consistently across the MANET).
Broadcast and multicast addresses, and addresses that are limited
in scope to less than the entire MANET, MUST NOT be considered as routable
addresses. Anycast addresses may be considered as routable addresses.
An address that is unique (within the MANET) to a router. A router
MUST select an originator address; it MAY choose one of its
interface addresses as its originator address; and it MAY select either
a routable or non-routable address. A broadcast, multicast, or anycast
address MUST NOT be chosen as an originator address. If the router
selects a routable address, then it MUST be one that the router will
accept as destination. An originator address MUST NOT have a prefix
length, except when included in an Address Block where it MAY be
associated with a prefix of maximum prefix length (e.g., if the originator
address is an IPv6 address, it MUST have either no prefix length or have a
prefix length of 128).
The originator address of the router that created a message, as deduced
from that message by its recipient. For all messages used in this
specification, including HELLO messages defined in ,
the recipient MUST be able to deduce an originator address. The message
originator address will usually be included in the message as its
<msg-orig-addr> element as defined in .
However, an exceptional case, which does not add a <msg-orig-addr>
element to a HELLO message, may be used by a router that only has a
single address.
A numerical value between WILL_NEVER and WILL_ALWAYS (both inclusive)
that represents the router's willingness to be selected as an MPR.
A router has separate willingness values to be a flooding MPR and
a routing MPR.
A symmetric 1-hop neighbor that has willingness not equal to WILL_NEVER.
A router, X, is an MPR for a router, Y, if router Y has indicated its
selection of router X as an MPR in a recent HELLO message. Router X may
be a flooding MPR for Y if it is indicated to participate in the
flooding process of messages received from router Y, or it may be a
routing MPR for Y if it is indicated to declare link state information
for the link from X to Y. It may also be both at the same time.
A router, Y, is a flooding/routing MPR selector of router X if router Y
has selected router X as a flooding/routing MPR.
The optimized MANET-wide information distribution mechanism, employed
by this protocol, in which a message is relayed by only a reduced subset
of the routers in the network. MPR flooding is the mechanism by which
flooding reduction is achieved.
Indicates that a timer is set to a value clearly preceding the current
time (e.g., current time - 1).
This specification employs the same notational conventions as
and .
This document specifies OLSRv2, a proactive routing protocol
intended for use in Mobile Ad Hoc Networks (MANETs) .
The protocol's applicability is determined by its characteristics, which are
that this protocol:
Is designed to work in networks with a dynamic topology and
in which messages may be lost, such as due to collisions over
wireless media.
Supports routers that each have one or more participating
OLSRv2 interfaces, which will consist of some or all of its MANET
interfaces using . The set of a router's
OLSRv2 interfaces, and the sets of its other MANET and non-MANET
interfaces, may change over time. Each interface may have one or
more network addresses (which may have prefix lengths), and these
may also be dynamically changing.
Enables hop-by-hop routing, i.e., each router can use its local
information provided by this protocol to route packets.
Continuously maintains routes to all destinations in the network,
i.e., routes are instantly available and data traffic is subject to
no delays due to route discovery. Consequently, no data traffic
buffering is required.
Supports routers that have non-OLSRv2 interfaces that may be
local to a router or that can serve as gateways towards other
networks.
Enables the use of bidirectional additive link metrics to use
shortest distance routes (i.e., routes with smallest total of
link metrics). Incoming link metric values are to be determined
by a process outside this specification.
Is optimized for large and dense networks; the larger and more
dense a network, the more optimization can be achieved by using
MPRs, compared to the classic link state algorithm .
Uses as described in its "Intended Usage"
appendix and by .
Allows "external" and "internal" extensibility (adding new Message
Types and adding information to existing messages) as enabled by
.
Is designed to work in a completely distributed manner and does
not depend on any central entity.
The objectives of this protocol are for each router to:
Identify all destinations in the network.
Identify a sufficient subset of links in the network, in order that
shortest routes can be calculated to all available destinations.
Provide a Routing Set containing these shortest routes from this router
to all destinations (routable addresses and local links).
These objectives are achieved, for each router, by:
Using NHDP to identify symmetric 1-hop neighbors and
symmetric 2-hop neighbors.
Reporting its participation in OLSRv2, and its willingness to be a flooding
MPR and to be a routing MPR, by extending the HELLO messages defined in
by the addition of an MPR_WILLING Message TLV. The
router's "flooding willingness" indicates how willing it is to participate
in MPR flooding. The router's "routing willingness" indicates how willing
it is to be an intermediate router for routing. Note that a router is
still able to be a routing source or destination, even if unwilling to
perform either function.
Extending the HELLO messages defined in to allow
the addition of directional link metrics to advertised links with other
routers participating in OLSRv2 and to indicate which link metric type is
being used by those routers. Both incoming and outgoing link metrics may be
reported, the former determined by the advertising router.
Selecting flooding MPRs and routing MPRs from among its willing
symmetric 1-hop neighbors such that, for each set of MPRs, all symmetric
2-hop neighbors are reachable either directly or via at least one selected
MPR, using a path of appropriate minimum total metric for at least routing
MPR selection. An analysis and examples of MPR selection algorithms are given
in ; a suggested algorithm, appropriately adapted for
each set of MPRs, is included in of this
specification. Note that it is not necessary for routers to use the
same algorithm in order to interoperate in the same MANET, but each such
algorithm must have the appropriate properties, described in
.
Signaling its flooding MPR and routing MPR selections, by extending the
HELLO messages defined in to report this information
by the addition of MPR Address Block TLV(s) associated with the appropriate
network addresses.
Extracting its flooding MPR selectors and routing MPR selectors from
received HELLO messages, using the included MPR Address Block TLV(s).
Defining a TC (Topology Control) Message Type using the message format
specified in . TC messages are used
to periodically signal links between routing MPR selectors and
itself throughout the MANET. This signaling includes suitable
directional neighbor metrics (the best link metric in that direction
between those routers).
Allowing its TC messages, as well as HELLO messages, to be included
in packets specified in , using the "manet"
IP protocol or UDP port as specified in .
Diffusing TC messages by using a flooding reduction mechanism,
denoted "MPR flooding"; only the flooding MPRs of a router will
retransmit messages received from (i.e., originated or last relayed
by) that router.
Note that the indicated extensions to are of
forms permitted by that specification.
This specification defines:
The requirement to use , its parameters,
constants, HELLO messages, and Information Bases, each as extended
in this specification.
Two new Information Bases: the Topology Information Base and the
Received Message Information Base.
TC messages, which are used for MANET wide signaling (using MPR
flooding) of selected topology (link state) information.
A requirement for each router to have an originator address to be
included in, or deducible from, HELLO messages and TC messages.
The specification of new Message TLVs and Address Block TLVs that
are used in HELLO messages and TC messages, including for reporting
neighbor status, MPR selection, external gateways, link metrics,
willingness to be an MPR, and content sequence numbers. Note that the
generation of (incoming) link metric values is to be undertaken by a
process outside this specification; this specification concerns only
the distribution and use of those metrics.
The generation of TC messages from the appropriate information in the
Information Bases.
The updating of the Topology Information Base according to received
TC messages.
The MPR flooding mechanism, including the inclusion of message
originator address and sequence number to manage duplicate messages,
using information recorded in the Received Message Information Base.
The response to other events, such as the expiration of information
in the Information Bases.
This protocol inherits the stability of a link state algorithm and has
the advantage of having routes immediately available when needed, due to
its proactive nature.
This protocol only interacts with IP through routing table management
and the use of the sending IP address for IP datagrams containing
messages used by this specification.
In order for a router to participate in a MANET using this protocol,
it must have at least one, and possibly more, OLSRv2 interfaces.
Each OLSRv2 interface:
Is a MANET interface, as specified in .
In particular, it must be configured with one or more network addresses;
these addresses must each be specific to this router and must include
any address that will be used as the sending address of any IP packet
sent on this OLSRv2 interface.
Has a number of interface parameters, adding to those specified in
.
Has an Interface Information Base, extending that specified in
.
Generates and processes HELLO messages according to ,
extended as specified in .
In addition to a set of OLSRv2 interfaces as described above, each router:
May have one or more non-OLSRv2 interfaces (which may include MANET
interfaces and/or non-MANET interfaces) and/or local attached networks
for which this router can accept IP packets. All routable addresses for which
the router is to accept IP packets must be used as an (OLSRv2 or non-OLSRv2)
interface network address or as an address of a local attached network of
the router.
Has a number of router parameters, adding to those specified in
.
Has a Local Information Base, extending that specified in
, including selection of an originator address
and recording any locally attached networks.
Has a Neighbor Information Base, extending that specified in
to record MPR selection and advertisement
information.
Has a Topology Information Base, recording information received in
TC messages.
Has a Received Message Information Base, recording information
about received messages to ensure that each TC message is only
processed once, and forwarded at most once on each OLSRv2 interface,
by a router.
Generates, receives, and processes TC messages.
Each router maintains the Information Bases described in the following
sections. These are used for describing the protocol in this
specification. An implementation of this protocol may maintain this
information in the indicated form or in any other organization that
offers access to this information. In particular, note that it is not
necessary to remove Tuples from Sets at the exact time indicated,
only to behave as if the Tuples were removed at that time.
The Local Information Base is specified in
and contains a router's local configuration. It is extended in this
specification to also record an originator address and to include
a router's:
Originator Set, containing addresses that were recently used as
this router's originator address, that is used, together with the
router's current originator address, to enable a router to recognize
and discard control traffic that was originated by the router itself.
Local Attached Network Set, containing network addresses of networks
to which this router can act as a gateway, that it advertises in its
TC messages.
The Interface Information Base for each OLSRv2 interface is as
specified in , extended to also
record, in each Link Set, link metric values (incoming and
outgoing) and flooding MPR selector information.
The Neighbor Information Base is specified in
and is extended to also record, in the Neighbor Tuple for each
neighbor:
Its originator address.
Neighbor metric values, these being the minimum of the link
metric values in the indicated direction for all symmetric 1-hop
links with that neighbor.
Its willingness to be a flooding MPR and to be a routing MPR.
Whether it has been selected by this router as a flooding MPR
or as a routing MPR and whether it is a routing MPR selector
of this router. (Whether it is a flooding MPR selector of this
neighbor is recorded in the Interface Information Base.)
Whether it is to be advertised in TC messages sent by this router.
The Topology Information Base in each router contains:
An Advertising Remote Router Set, recording each remote router from
which TC messages have been received. This is used in order to
determine if a received TC message contains fresh or outdated
information; a received TC message is ignored in the latter case.
A Router Topology Set, recording links between routers in the MANET,
as described by received TC messages.
A Routable Address Topology Set, recording routable addresses in the
MANET (available as IP packet destinations) and from which remote router
these routable addresses can be directly reached (i.e., in a single
IP hop from that remote router), as reported by received TC messages.
An Attached Network Set, recording networks to which a remote router
has advertised that it may act as a gateway. These networks may be
reached in one or more IP hops from that remote router.
A Routing Set, recording routes from this router to all available
destinations. The IP routing table is to be updated using this Routing Set.
(A router may choose to use any or all destination network addresses in the
Routing Set to update the IP routing table. This selection is outside the
scope of this specification.)
The purpose of the Topology Information Base is to record information
used, in addition to that in the Local Information Base, the
Interface Information Bases, and the Neighbor Information Base, to
construct the Routing Set (which is also included in the Topology
Information Base).
This specification describes the calculation of the Routing Set based on
a Topology Graph constructed in two phases. First, a "backbone" graph
representing the routers in the MANET, and the connectivity between them,
is constructed from the Local Information Base, the Neighbor Information Base,
and the Router Topology Set. Second, this graph is "decorated" with additional
destination network addresses using the Local Information Base, the Routable
Address Topology Set, and the Attached Network Set.
The Topology Graph does not need to be recorded in the Topology Information Base;
it can either be constructed as required when the Routing Set is to be changed
or need not be explicitly constructed (as illustrated in ).
An implementation may, however, construct and retain the Topology Graph if preferred.
The Received Message Information Base in each router contains:
A Received Set for each OLSRv2 interface, describing TC messages
received by this router on that OLSRv2 interface.
A Processed Set, describing TC messages processed by this router.
A Forwarded Set, describing TC messages forwarded by this router.
The Received Message Information Base serves the MPR flooding mechanism
by ensuring that received messages are forwarded at most once by a
router
and also ensures that received messages are processed exactly once by a
router. The Received Message Information Base may also record information
about other Message Types that use the MPR flooding mechanism.
This protocol generates and processes HELLO messages according to
. HELLO messages transmitted on OLSRv2 interfaces
are extended according to
of this specification to include an originator address, link metrics, and
MPR selection information.
This specification defines a single Message Type, the TC message.
TC messages are sent by their originating router proactively, at a
regular interval, on all OLSRv2 interfaces. This interval may be fixed
or dynamic, for example, it may be backed off due to congestion
or network stability. TC messages may also be sent as a response to a
change in the router itself, or its advertised symmetric 1-hop neighborhood,
for example, on first being selected as a routing MPR.
Because TC messages are sent periodically, this protocol is tolerant
of unreliable transmissions of TC messages. Message losses may occur more
frequently in wireless networks due to collisions or other transmission
problems. This protocol may use "jitter", randomized adjustments to
message transmission times, to reduce the incidence of collisions, as
specified in .
This protocol is tolerant of out-of-sequence delivery of TC messages
due to in-transit message reordering. Each router maintains an
Advertised Neighbor Sequence Number (ANSN) that is incremented when
its recorded neighbor information that is to be included in its TC
messages changes. This ANSN is included in the router's TC messages.
The recipient of a TC message can use this included ANSN to identify
which of the information it has received is most recent, even if
messages have been reordered while in transit. Only the most recent
information received is used; older information received later is
discarded.
TC messages may be "complete" or "incomplete". A complete TC message
advertises all of the originating router's routing MPR selectors; it
may also advertise other symmetric 1-hop neighbors. Complete TC messages
are generated periodically (and also, optionally, in response to
symmetric 1-hop neighborhood changes). Incomplete TC messages may be
used to report additions to advertised information, without repeating
unchanged information.
TC messages, and HELLO messages as extended by this specification,
define (by inclusion or by deduction when having a single address)
an originator address for the router that created the message.
A TC message reports both the originator addresses and routable addresses
of its advertised neighbors, distinguishing the two using an Address
Block TLV (an address may be both routable and an originator address).
TC messages also report the originator's locally attached networks.
TC messages are MPR flooded throughout the MANET. A router retransmits
a TC message received on an OLSRv2 interface if and only if the message
did not originate at this router and has not been previously forwarded
by this router, this is the first time the message has been received on
this OLSRv2 interface, and the message is received from (i.e., originated
from or was last relayed by) one of this router's flooding MPR selectors.
Some TC messages may be MPR flooded over only part of the network,
e.g., allowing a router to ensure that nearer routers are kept more up
to date than distant routers, such as is used in Fisheye State Routing
and Fuzzy Sighted Link State routing
. This is enabled using .
TC messages include outgoing neighbor metrics that will be used in the
selection of routes.
OLSRv1 created minimum hop routes to destinations.
However, in many, if not most, circumstances, better routes (in terms of
quality of service for end users) can be created by use of link metrics.
OLSRv2, as defined in this specification, supports metric-based routing,
i.e., it allows links to each have a chosen metric. Link metrics as
defined in OLSRv2 are additive, and the routes that are to be created
are those with the minimum sum of the link metrics along that route.
Link metrics are defined to be directional; the link metric from
one router to another may be different from that on the reverse link.
The link metric is assessed at the receiver, as on a (typically) wireless
link, that is the better informed as to link information. Both incoming
and outgoing link information is used by OLSRv2; the distinctions in this
specification must be clearly followed.
This specification also defines both incoming and outgoing neighbor metrics
for each symmetric 1-hop neighbor, these being the minimum value of the link
metrics in the same direction for all symmetric links with that neighbor.
Note that this means that all neighbor metric values are link metric values
and that specification of, for example, link metric value encoding also
includes encoding of neighbor metric values.
This specification does not define the nature of the link metric. However,
this specification allows, through use of the type extension of a defined
Address Block TLV, for link metrics with specific meanings to be defined
and either allocated by IANA or privately used. Each HELLO or TC message
carrying link (or neighbor) metrics thus indicates which
link metric information it is carrying, allowing routers to
determine if they can interoperate. If link metrics require additional
signaling to determine their values, whether in HELLO messages or
otherwise, then this is permitted but is outside the scope of this
specification.
Careful consideration should be given to how to use link metrics. In
particular, it is advisable to not simply default to use of all links
with equal metrics (i.e., hop count) for routing without careful
consideration of whether that is appropriate or not.
This specification uses two sets of MPRs: flooding MPRs and routing MPRs. These are selected separately, because:
Flooding MPRs may use metrics; routing MPRs must use metrics.
When flooding MPRs use metrics, these are outgoing link metrics;
routing MPRs use incoming neighbor metrics.
Flooding MPRs must be selected per OLSRv2 interface; routing
MPRs need not be selected per OLSRv2 interface.
The purpose of the Routing Set is to determine and record routes
(local interface network address and next-hop interface network
address) to all possible routable addresses advertised by this
protocol as well as all destinations that are local, i.e.,
within one hop, to the router (whether using routable addresses
or not). Only symmetric links are used in such routes.
It is intended that the Routing Set can be used for IP packet routing,
by using its contents to update the IP routing table. That
update, and whether any Routing Tuples are not used when updating the IP
routing table, is outside the scope of this specification.
The signaling in this specification has been designed so that a
"backbone" Topology Graph of routers, each identified by its
originator address, with at most one direct connection between any
pair of routers, can be constructed (from the Neighbor Set and the
Router Topology Set) using a suitable minimum path length algorithm.
This Topology Graph can then have other network addresses (routable
or of symmetric 1-hop neighbors) added to it (using the Interface
Information Bases, the Routable Address Topology Set, and the Attached
Network Set).
The parameters and constants used in this specification are those
defined in plus those defined in this section.
The separation in into interface parameters,
router parameters, and constants is also used in this specification.
Similarly to the parameters in , parameters defined in this
specification MAY be changed dynamically by a router
and need not be
the same on different routers, even in the same MANET, or, for
interface parameters, on different interfaces of the
same router.
This protocol specifies TC messages, which are included in packets as
defined by . These packets MUST be sent either
using the "manet" protocol number or the "manet" UDP well-known port
number, as specified in .
TC messages and HELLO messages MUST,
in a given MANET, either both use IP or both use UDP,
in order for it to be possible to combine messages of both protocols
into the same packet for transmission.
This protocol specifies TC messages, which are included in packets as
defined by . These packets MAY be transmitted
using the Link-Local multicast address "LL-MANET-Routers", as specified
in .
A single additional interface parameter is specified for OLSRv2 interfaces
only.
The following parameter manages the validity time of recorded
received message information:
The period after receipt of a message by the appropriate
OLSRv2 interface of this router for which that information
is recorded, in order that the message is recognized as having
been previously received on this OLSRv2 interface.
The following constraints apply to this parameter:
RX_HOLD_TIME > 0
RX_HOLD_TIME SHOULD be greater than the maximum difference
in time that a message may take to traverse the MANET, taking
into account any message forwarding jitter as well as propagation,
queuing, and processing delays.
The following router parameters are specified for routers.
The following router parameter manages the time for which local information
is retained:
The time for which a recently used and replaced originator address
is used to recognize the router's own messages.
The following constraint applies to this parameter:
O_HOLD_TIME > 0
All routes found using this specification use a single link
metric type that is specified by the router parameter
LINK_METRIC_TYPE, which may take any value from 0 to 255,
both inclusive.
The following parameters regulate TC message transmissions by a router.
TC messages are usually sent periodically but MAY also be sent in response
to changes in the router's Neighbor Set and/or Local Attached Network Set.
In a highly dynamic network, and with a larger value of the parameter
TC_INTERVAL and a smaller value of the parameter TC_MIN_INTERVAL,
TC messages MAY be transmitted more often in response to changes than
periodically. However, because a router has no knowledge of, for example,
routers remote to it (i.e., beyond two hops away) joining the network,
TC messages MUST NOT be sent purely responsively.
The maximum time between the transmission of two
successive TC messages by this router. When no TC messages are
sent in response to local network changes (by design or because
the local network is not changing), then TC messages MUST be sent
at a regular interval TC_INTERVAL, possibly modified by jitter, as
specified in .
The minimum interval between transmission of two successive
TC messages by this router. (This minimum interval MAY be modified
by jitter, as specified in .)
The following constraints apply to these parameters:
TC_INTERVAL > 0
0 <= TC_MIN_INTERVAL <= TC_INTERVAL
If TLVs with Type = INTERVAL_TIME, as defined in
, are included in TC messages,
then TC_INTERVAL MUST be representable by way of the
exponent-mantissa notation described in Section 5 of
.
The following parameters manage the validity time of information advertised
in TC messages:
Used as the minimum value in the TLV with Type = VALIDITY_TIME
included in all TC messages sent by this router. If a single value of
parameter TC_HOP_LIMIT (see ) is used, then this
will be the only value in that TLV.
The period during which TC messages are sent after they no longer
have any advertised information to report but are sent in order to
accelerate outdated information removal by other routers.
The following constraints apply to these parameters:
T_HOLD_TIME > 0
A_HOLD_TIME >= 0
T_HOLD_TIME >= TC_INTERVAL
If TC messages can be lost, then both T_HOLD_TIME and A_HOLD_TIME SHOULD be
significantly greater than TC_INTERVAL; a value >= 3 x TC_INTERVAL is RECOMMENDED.
T_HOLD_TIME MUST be representable by way of the exponent-mantissa notation
described in Section 5 of .
The following parameters manage the processing and forwarding validity time of
recorded message information:
The period after receipt of a message that is processed by this router for
which that information is recorded, in order that the message is not processed
again if received again.
The period after receipt of a message that is forwarded by this router for
which that information is recorded, in order that the message is not forwarded
again if received again.
The following constraints apply to these parameters:
P_HOLD_TIME > 0
F_HOLD_TIME > 0
Both of these parameters SHOULD be greater than the maximum difference in time that
a message may take to traverse the MANET, taking into account any message forwarding
jitter as well as propagation, queuing, and processing delays.
If jitter, as defined in , is used, then the governing jitter
parameters are as follows:
Represents the value of MAXJITTER used in
for periodically generated TC messages sent by this router.
Represents the value of MAXJITTER used in
for externally triggered TC messages sent by this router.
Represents the default value of MAXJITTER used in
for messages forwarded by this router. However, before using F_MAXJITTER, a router
MAY attempt to deduce a more appropriate value of MAXJITTER, for example, based
on any TLVs with Type = INTERVAL_TIME or Type = VALIDITY_TIME contained in the
message to be forwarded.
For constraints on these parameters, see .
The parameter TC_HOP_LIMIT is the hop limit set in each TC message.
TC_HOP_LIMIT MAY be a single fixed value or MAY be different in
TC messages sent by the same router. However, each other router, at
any hop count distance, MUST see a regular pattern of TC messages
in order that meaningful values of TLVs with Type = INTERVAL_TIME
and Type = VALIDITY_TIME at each hop count distance can be included
as defined in . Thus, the pattern of TC_HOP_LIMIT
MUST be defined to have this property. For example, the repeating
pattern (255 4 4) satisfies this property (having period TC_INTERVAL
at hop counts up to 4, inclusive, and 3 x TC_INTERVAL at hop counts
greater than 4), but the repeating pattern (255 255 4 4) does not
satisfy this property because at hop counts greater than 4, message
intervals are alternately TC_INTERVAL and 3 x TC_INTERVAL.
The following constraints apply to this parameter:
The maximum value of TC_HOP_LIMIT >= the network diameter in hops;
a value of 255 is RECOMMENDED. Note that if using a pattern of
different values of TC_HOP_LIMIT as described above, then only the
maximum value in the pattern is so constrained.
All values of TC_HOP_LIMIT >= 2.
Each router has two willingness parameters: WILL_FLOODING and WILL_ROUTING,
each of which MUST be in the range WILL_NEVER to WILL_ALWAYS, inclusive.
WILL_FLOODING represents the router's willingness to be selected as a
flooding MPR and hence to participate in MPR flooding, in particular
of TC messages.
WILL_ROUTING represents the router's willingness to be selected as a
routing MPR and hence to be an intermediate router on routes.
In either case, the higher the value, the greater the router's willingness
to be a flooding or routing MPR, as appropriate. If a router has a willingness
value of WILL_NEVER (the lowest possible value), it does not perform the
corresponding task.
A MANET using
this protocol with too many routers having either of the willingness
parameters
WILL_FLOODING or WILL_ROUTING equal to WILL_NEVER will not function;
it MUST be ensured, by administrative or other means, that this does not happen.
Note that the proportion at which the routers having a willingness value equal to
WILL_NEVER is "too many" depends on the network topology -- which, in
a MANET, may change dynamically.
Willingness is intended to enable that certain routers (e.g.,
routers that have generous resources, such as a permanent power supply) can be
configured to assume more of the network operation, while others (e.g., routers
that have lesser resources, such as are battery operated) can avoid such tasks.
A general guideline would be that only if a router is not actually able to assume the task (flooding or routing) should it be configured with the corresponding
willingness WILL_NEVER.
If a router has a willingness value equal to WILL_ALWAYS (the highest possible
value), then it will always be selected as a flooding or routing MPR,
as appropriate,
by all symmetric 1-hop neighbors.
In a MANET in which all routers have WILL_FLOODING = WILL_ALWAYS, flooding reduction
will effectively be disabled, and flooding will perform as blind flooding.
In a MANET in which all routers have WILL_ROUTING = WILL_ALWAYS, topology reduction
will effectively be disabled, and all routers will advertise all of their links in
TC messages.
A router that has WILL_ROUTING = WILL_NEVER will not act as an intermediate router
in the MANET. Such a router can act as a source, destination, or gateway to another
routing domain.
Different routers MAY have different values for WILL_FLOODING and/or WILL_ROUTING.
The following constraints apply to these parameters:
WILL_NEVER <= WILL_FLOODING <= WILL_ALWAYS
WILL_NEVER <= WILL_ROUTING <= WILL_ALWAYS
If protocol parameters are changed dynamically, then the constraints in this section apply.
If RX_HOLD_TIME for an OLSRv2 interface changes, then the expiry time
for all Received Tuples for that OLSRv2 interface MAY be changed.
If O_HOLD_TIME changes, then the expiry time for all Originator Tuples
MAY be changed.
If TC_INTERVAL increases, then the next TC message
generated by this router MUST be generated according to the previous,
shorter TC_INTERVAL. Additional subsequent TC messages MAY be
generated according to the previous, shorter, TC_INTERVAL.
If TC_INTERVAL decreases, then the following TC
messages from this router MUST be generated according to the
current, shorter, TC_INTERVAL.
If P_HOLD_TIME changes, then the expiry time for all Processed Tuples MAY
be changed.
If F_HOLD_TIME changes, then the expiry time for all Forwarded Tuples MAY
be changed.
If TP_MAXJITTER changes, then the periodic TC message schedule
on this router MAY be changed immediately.
If TT_MAXJITTER changes, then externally triggered TC messages
on this router MAY be rescheduled.
If F_MAXJITTER changes, then TC messages waiting to be forwarded
with a delay based on this parameter MAY be rescheduled.
If TC_HOP_LIMIT changes, and the router uses multiple values after the
change, then message intervals and validity times included in TC messages
MUST be respected. The simplest way to do this is to start any new
repeating pattern of TC_HOP_LIMIT values with its largest value.
If LINK_METRIC_TYPE changes, then all link metric information
recorded by the router is invalid. The router MUST take the following
actions and all consequent actions described in
and .
For each Link Tuple in any Link Set for an OLSRv2 interface, either
update L_in_metric (the value MAXIMUM_METRIC MAY be used) or remove
the Link Tuple from the Link Set.
For each Link Tuple that is not removed, set:
L_out_metric := UNKNOWN_METRIC;
L_SYM_time := EXPIRED;
L_MPR_selector := false.
Remove all Router Topology Tuples, Routable Address Topology Tuples,
Attached Network Tuples, and Routing Tuples from their respective
Protocol Sets in the Topology Information Base.
The following constants are specified for routers. Unlike router parameters,
constants MUST NOT change and MUST be the same on all routers.
The constant minimum and maximum link metric values are defined by:
MINIMUM_METRIC := 1MAXIMUM_METRIC := 16776960
The symbolic value UNKNOWN_METRIC is defined in .
The constant minimum, RECOMMENDED default, and maximum willingness values are defined by:
WILL_NEVER := 0WILL_DEFAULT := 7WILL_ALWAYS := 15
The constant C (time granularity) is used as specified in . It MUST be the same
as is used by , with RECOMMENDED value:
C := 1/1024 second
Note that this constant is used in the representation of time intervals. Time values
(such as are stored in Protocol Tuples) are not so represented. A resolution of C in
such values is sufficient (but not necessary) for such values.
A router records a link metric value for each direction of a link of which it has knowledge. These link metric values are used to create metrics for routes by the addition of link metric values.
Link metrics are reported in messages using a compressed representation
that occupies 12 bits, consisting of a 4-bit field and an 8-bit field. The
compressed representation represents positive integer values with a minimum
value of 1 and a maximum value that is slightly smaller than the maximum 24-bit
value. Only those values that have exact representation in the compressed
form are used. Route metrics are the summation of no more than 256 link metric values and can therefore be represented using no more than 32 bits.
Link and route metrics used in the Information Bases defined in this
specification refer to the uncompressed values, and arithmetic involving them
does likewise and assumes full precision in the result. (How an implementation
records the values is not part of this specification, as long as it behaves as
if recording uncompressed values. An implementation can, for example, use
32-bit values for all link and route metrics.)
In some cases, a link metric value may be unknown. This is indicated in
this specification by the symbolic value UNKNOWN_METRIC. An implementation may
use any representation of UNKNOWN_METRIC as it is never included in messages
or used in any computation. (Possible representations are zero or any value
greater than the maximum representable metric value.)
The 12-bit compressed form of a link metric uses a modified form of a
representation with an 8-bit mantissa (denoted a) and a 4-bit exponent (denoted
b). Note that if represented as the 12-bit value 256b+a, then the ordering of
those 12-bit values is identical to the ordering of the represented values.
The value so represented is (257+a)2^b - 256, where ^ denotes exponentiation. This has a minimum value (when a = 0 and b = 0) of MINIMUM_METRIC = 1 and a maximum value (when a = 255 and b = 15) of MAXIMUM_METRIC = 2^24 - 256.
An algorithm for computing a and b for the smallest representable value not less than a link metric value v such that MINIMUM_METRIC <= v <= MAXIMUM_METRIC is:
Find the smallest integer b such that v + 256 <= 2^(b + 9).
Set a := (v - 256(2^b - 1)) / (2^b) - 1, rounded up to the nearest integer.
The Local Information Base, as defined for each router in ,
is extended by this protocol by:
Recording the router's originator address. The originator address
MUST be unique to this router. It MUST NOT be used by any other
router as an originator address. It MAY be included in any network
address in any I_local_iface_addr_list of this router; it MUST NOT
be included in any network address in any I_local_iface_addr_list
of any other router. It MAY be included in, but MUST NOT be equal to,
the AL_net_addr in any Local Attached Network Tuple in this or any
other router.
The addition of an Originator Set, defined in
, and a Local Attached Network Set,
defined in .
All routable addresses of the router for which it is to accept IP packets
as destination MUST be included in the Local Interface Set or the Local
Attached Network Set.
A router's Originator Set records addresses that were recently
used as originator addresses by this router. If a router's
originator address is immutable, then the Originator Set is always
empty and MAY be omitted. It consists of Originator Tuples:
(O_orig_addr, O_time)
where:
O_orig_addr is a recently used originator address; note that this does not
include a prefix length.
O_time specifies the time at which this Tuple expires and MUST be removed.
A router's Local Attached Network Set records its local non-OLSRv2
interfaces via which it can act as a gateway to other networks. The
Local Attached Network Set MUST be provided to this protocol and MUST
reflect any changes in the router's status. (In cases where the
router's configuration is static, the Local Attached Network Set will
be constant; in cases where the router has no such non-OLSRv2 interfaces,
the Local Attached Network Set will be empty.) The Local Attached
Network Set is not modified by this protocol. This protocol
will respond to (externally provided) changes to the Local Attached
Network Set. It consists of Local Attached Network Tuples:
(AL_net_addr, AL_dist, AL_metric)
where:
AL_net_addr is the network address of an attached network that can be reached
via this router. This SHOULD be a routable address. It is constrained
as described below.
AL_dist is the number of hops to the network with network address AL_net_addr
from this router.
AL_metric is the metric of the link to the attached network with address
AL_net_addr from this router.
Attached networks local to this router only (i.e., not reachable except
via this router) SHOULD be treated as local non-MANET interfaces and
added to the Local Interface Set, as specified in ,
rather than added to the Local Attached Network Set.
Because an attached network is not specific to the router and may be
outside the MANET, an attached network MAY also be attached to other
routers. Routing to an AL_net_addr will use maximum prefix length
matching; consequently, an AL_net_addr MAY include, but MUST NOT equal
or be included in, any network address that is of any interface of
any router (i.e., is included in any I_local_iface_addr_list) or equal
any router's originator address.
It is not the responsibility of this protocol to maintain routes from
this router to networks recorded in the Local Attached Network Set.
Local Attached Network Tuples are removed from the Local Attached
Network Set only when the router's local attached network
configuration changes, i.e., they are not subject to timer-based
expiration or changes due to received messages.
An Interface Information Base, as defined in , is
maintained for each MANET interface. The Link Set and 2-Hop Set in the
Interface Information Base for an OLSRv2 interface are modified by this
protocol. In some cases, it may be convenient to consider these Sets as
also containing these additional elements for other MANET interfaces,
taking the indicated values on creation but never being updated.
The Link Set is modified by adding these additional elements to each Link Tuple:
L_in_metric is the metric of the link from the OLSRv2 interface
with addresses L_neighbor_iface_addr_list to this OLSRv2 interface;
L_out_metric is the metric of the link to the OLSRv2 interface
with addresses L_neighbor_iface_addr_list from this OLSRv2 interface;
L_mpr_selector is a boolean flag, describing if this neighbor has
selected this router as a flooding MPR, i.e., is a flooding MPR
selector of this router.
L_in_metric will be specified by a process that is external to this
specification. Any Link Tuple with L_status = HEARD or
L_status = SYMMETRIC MUST have a specified value of L_in_metric
if it is to be used by this protocol.
A Link Tuple created (but not updated) by MUST set:
L_in_metric := UNKNOWN_METRIC; L_out_metric := UNKNOWN_METRIC; L_mpr_selector := false.
The 2-Hop Set is modified by adding these additional elements to each 2-Hop Tuple:
N2_in_metric is the neighbor metric from the router with address N2_2hop_iface_addr to the router with OLSRv2 interface addresses N2_neighbor_iface_addr_list;
N2_out_metric is the neighbor metric to the router with address N2_2hop_iface_addr from the router with OLSRv2 interface addresses N2_neighbor_iface_addr_list.
A 2-Hop Tuple created (but not updated) by MUST set:
N2_in_metric := UNKNOWN_METRIC; N2_out_metric := UNKNOWN_METRIC.
A Neighbor Information Base, as defined in , is
maintained for each router. It is modified by this protocol by adding
these additional elements to each Neighbor Tuple in the Neighbor Set.
In some cases, it may be convenient to consider these Sets as
also containing these additional elements for other MANET interfaces,
taking the indicated values on creation but never being updated.
N_orig_addr is the neighbor's originator address, which may be unknown. Note
that this originator address does not include a prefix length;
N_in_metric is the neighbor metric of any link from this neighbor to an
OLSRv2 interface of this router, i.e., the minimum of all corresponding
L_in_metric with L_status = SYMMETRIC and L_in_metric != UNKNOWN_METRIC,
UNKNOWN_METRIC if there are no such Link Tuples;
N_out_metric is the neighbor metric of any link from an OLSRv2 interface
of this router to this neighbor, i.e., the minimum of all corresponding
L_out_metric with L_status = SYMMETRIC and L_out_metric != UNKNOWN_METRIC,
UNKNOWN_METRIC if there are no such Link Tuples;
N_will_flooding is the neighbor's willingness to be selected as a flooding MPR,
in the range from WILL_NEVER to WILL_ALWAYS, both inclusive, taking the value
WILL_NEVER if no OLSRv2-specific information is received from this neighbor;
N_will_routing is the neighbor's willingness to be selected as a routing MPR,
in the range from WILL_NEVER to WILL_ALWAYS, both inclusive, taking the value
WILL_NEVER if no OLSRv2-specific information is received from this neighbor;
N_flooding_mpr is a boolean flag, describing if this neighbor is selected as a flooding
MPR by this router;
N_routing_mpr is a boolean flag, describing if this neighbor is selected as a routing
MPR by this router;
N_mpr_selector is a boolean flag, describing if this neighbor has selected this
router as a routing MPR, i.e., is a routing MPR selector of this router.
N_advertised is a boolean flag, describing if this router has elected to
advertise a link to this neighbor in its TC messages.
A Neighbor Tuple created (but not updated) by
MUST set:
N_orig_addr := unknown; N_in_metric := UNKNOWN_METRIC; N_out_metric := UNKNOWN_METRIC; N_will_flooding := WILL_NEVER; N_will_routing := WILL_NEVER; N_routing_mpr := false; N_flooding_mpr := false; N_mpr_selector := false; N_advertised := false.
The Neighbor Information Base also includes a variable, the Advertised
Neighbor Sequence Number (ANSN), whose value is included in TC messages
to indicate the freshness of the information transmitted. The ANSN is
incremented whenever advertised information (the originator and
routable addresses included in Neighbor Tuples with N_advertised = true
and local attached networks recorded in the Local Attached Network Set
in the Local Information Base) changes, including addition or removal
of such information.
The Topology Information Base, defined for each router by this
specification, stores information received in TC messages in the
Advertising Remote Router Set, the Router Topology Set, the Routable
Address Topology Set, and the Attached Network Set.
Additionally, a Routing Set is maintained, derived from the information
recorded in the Local Information Base, the Interface Information Bases,
the Neighbor Information Base, and the rest of the Topology Information Base.
A router's Advertising Remote Router Set records information
describing each remote router in the network that transmits
TC messages, allowing outdated TC messages to be recognized
and discarded. It consists of Advertising Remote Router Tuples:
(AR_orig_addr, AR_seq_number, AR_time)
where:
AR_orig_addr is the originator address of a received TC message, note that
this does not include a prefix length;
AR_seq_number is the greatest ANSN in any TC message received that originated
from the router with originator address AR_orig_addr (i.e., that
contributed to the information contained in this Tuple);
AR_time is the time at which this Tuple expires and MUST be removed.
A router's Topology Set records topology information about the
links between routers in the MANET. It consists of Router Topology Tuples:
(TR_from_orig_addr, TR_to_orig_addr, TR_seq_number, TR_metric,
TR_time)
where:
TR_from_orig_addr is the originator address of a router that can reach the router
with originator address TR_to_orig_addr in one hop (note that this
does not include a prefix length);
TR_to_orig_addr is the originator address of a router that can be
reached by the router with originator address TR_from_orig_addr in
one hop (note that this does not include a prefix length);
TR_seq_number is the greatest ANSN in any TC message received that originated
from the router with originator address TR_from_orig_addr (i.e.,
that contributed to the information contained in this Tuple);
TR_metric is the neighbor metric from the router with originator address
TR_from_orig_addr to the router with originator address
TR_to_orig_addr;
TR_time specifies the time at which this Tuple expires and MUST be removed.
A router's Routable Address Topology Set records topology information
about the routable addresses within the MANET, including via which routers
they may be reached. It consists of Routable Address Topology Tuples:
(TA_from_orig_addr, TA_dest_addr, TA_seq_number, TA_metric,
TA_time)
where:
TA_from_orig_addr is the originator address of a router that can reach the router with
routable address TA_dest_addr in one hop (note that this does not
include a prefix length);
TA_dest_addr is a routable address of a router that can be reached by the router
with originator address TA_from_orig_addr in one hop;
TA_seq_number is the greatest ANSN in any TC message received that originated
from the router with originator address TA_from_orig_addr (i.e.,
that contributed to the information contained in this Tuple);
TA_metric is the neighbor metric from the router with originator address
TA_from_orig_addr to the router with OLSRv2 interface address
TA_dest_addr;
TA_time specifies the time at which this Tuple expires and MUST be removed.
A router's Attached Network Set records information about networks
(which may be outside the MANET) attached to other routers and their
routable addresses. It consists of Attached Network Tuples:
(AN_orig_addr, AN_net_addr, AN_seq_number, AN_dist, AN_metric,
AN_time)
where:
AN_orig_addr is the originator address of a router that can act as gateway to
the network with network address AN_net_addr (note that this does
not include a prefix length);
AN_net_addr is the network address of an attached network that may be reached
via the router with originator address AN_orig_addr;
AN_seq_number is the greatest ANSN in any TC message received that originated
from the router with originator address AN_orig_addr (i.e., that
contributed to the information contained in this Tuple);
AN_dist is the number of hops to the network with network address AN_net_addr
from the router with originator address AN_orig_addr;
AN_metric is the metric of the link from the router with originator address
AN_orig_addr to the attached network with address AN_net_addr;
AN_time specifies the time at which this Tuple expires and MUST be removed.
A router's Routing Set records the first hop along a selected path to
each destination for which any such path is known. It consists of
Routing Tuples:
(R_dest_addr, R_next_iface_addr, R_local_iface_addr, R_dist,
R_metric)
where:
R_dest_addr is the network address of the destination, either the network address
of an interface of a destination router or the network address of an
attached network;
R_next_iface_addr is the network address of the "next hop" on the selected path to the destination;
R_local_iface_addr is an address of the local interface over which an IP packet
MUST be sent to reach the destination by the selected path.
R_dist is the number of hops on the selected path to the destination;
R_metric is the metric of the route to the destination with address R_dest_addr.
The Routing Set for a router is derived from the contents of other Protocol
Sets of the router (the Link Sets, the Neighbor Set, the Router Topology Set,
the Routable Address Topology Set, the Attached Network Set, and OPTIONAL use of
the 2-Hop Sets). The Routing Set is updated (Routing Tuples added or removed,
or the complete Routing Set recalculated) when routing paths are calculated,
based on changes to these other Protocol Sets. Routing Tuples are not subject
to timer-based expiration.
The Received Message Information Base, defined by this specification,
records information required to ensure that a message is processed at
most once and is forwarded at most once per OLSRv2 interface of a router,
using MPR flooding. Messages are recorded using their "signature",
consisting of their type, originator address, and message sequence number.
A router has a Received Set per OLSRv2 interface. Each Received Set
records the signatures of messages that have been received over that
OLSRv2 interface. Each consists of Received Tuples:
(RX_type, RX_orig_addr, RX_seq_number, RX_time)
where:
RX_type is the received Message Type;
RX_orig_addr is the originator address of the received message (note that
this does not include a prefix length);
RX_seq_number is the message sequence number of the received message;
RX_time specifies the time at which this Tuple expires and MUST be removed.
A router has a single Processed Set that records signatures of messages
that have been processed by the router. It consists of Processed Tuples:
(P_type, P_orig_addr, P_seq_number, P_time)
where:
P_type is the processed Message Type;
P_orig_addr is the originator address of the processed message (note that
this does not include a prefix length);
P_seq_number is the message sequence number of the processed message;
P_time specifies the time at which this Tuple expires and MUST be removed.
A router has a single Forwarded Set that records signatures of messages
that have been forwarded by the router. It consists of Forwarded Tuples:
(F_type, F_orig_addr, F_seq_number, F_time)
where:
F_type is the forwarded Message Type;
F_orig_addr is the originator address of the forwarded message (note that
this does not include a prefix length);
F_seq_number is the message sequence number of the forwarded message;
F_time specifies the time at which this Tuple expires and MUST be removed.
This section describes some additional properties of Information Bases
and their contents.
As part of this specification, in a number of cases, there is a natural
correspondence from a Protocol Tuple in one Protocol Set to a single
Protocol Tuple in another Protocol Set, in the same or another Information
Base. The latter Protocol Tuple is referred to as "corresponding" to the
former Protocol Tuple.
Specific examples of corresponding Protocol Tuples include:
There is a Local Interface Tuple corresponding to each Link Tuple,
where the Link Tuple is in the Link Set for a MANET interface
and the Local Interface Tuple represents that MANET interface.
There is a Neighbor Tuple corresponding to each Link Tuple that
has L_HEARD_time not EXPIRED, such that N_neighbor_addr_list
contains L_neighbor_iface_addr_list.
There is a Link Tuple (in the Link Set in the same Interface
Information Base) corresponding to each 2-Hop Tuple such that
L_neighbor_iface_addr_list = N2_neighbor_iface_addr_list.
There is a Neighbor Tuple corresponding to each 2-Hop Tuple,
such that N_neighbor_addr_list contains N2_neighbor_iface_addr_list.
(This is the Neighbor Tuple corresponding to the Link Tuple
corresponding to the 2-Hop Tuple.)
There is an Advertising Remote Router Tuple corresponding to each
Router Topology Tuple such that AR_orig_addr = TR_from_orig_addr.
There is an Advertising Remote Router Tuple corresponding to each
Routable Address Topology Tuple such that AR_orig_addr = TA_from_orig_addr.
There is an Advertising Remote Router Tuple corresponding to each
Attached Network Tuple such that AR_orig_addr = AN_orig_addr.
There is a Neighbor Tuple corresponding to each Routing Tuple
such that N_neighbor_addr_list contains R_next_iface_addr.
Addresses or network addresses with the following properties are considered as
"fully owned" by a router when processing a received message:
Equaling its originator address; OR
Equaling the O_orig_addr in an Originator Tuple; OR
Equaling or being a sub-range of the I_local_iface_addr_list in a Local
Interface Tuple; OR
Equaling or being a sub-range of the IR_local_iface_addr in a Removed
Interface Address Tuple; OR
Equaling an AL_net_addr in a Local Attached Network Tuple.
Addresses or network addresses with the following properties are considered as
"partially owned" (which may include being fully owned) by a router when processing
a received message:
Overlapping (equaling or containing) its originator address; OR
Overlapping (equaling or containing) the O_orig_addr in an Originator
Tuple; OR
Overlapping the I_local_iface_addr_list in a Local Interface Tuple; OR
Overlapping the IR_local_iface_addr in a Removed Interface Address
Tuple; OR
Equaling or having as a sub-range an AL_net_addr in a Local Attached Network Tuple.
The packet and message format used by this protocol is defined
in . Except as otherwise noted, options
defined in may be freely used, in particular
alternative formats defined by packet, message, Address Block, and
TLV flags.
This section describes the usage of the packets and messages defined
in by this specification and the TLVs
defined by, and used in, this specification.
Routers using this protocol exchange information through messages.
The Message Types used by this protocol are the HELLO message and
the TC message. The HELLO message is defined by
and extended by this specification (see ).
The TC message is defined by this specification (see ).
One or more messages sent by a router at the same time SHOULD be combined
into a single packet, subject to any constraints on maximum packet size
(such as derived from the MTU over a local single hop) that MAY be imposed.
These messages may have originated at the sending router or
at another router and are being forwarded by the sending router. Messages
with different originating routers MAY be combined for transmission within
the same packet. Messages from other protocols defined using ,
including but not limited to NHDP , MAY be combined for
transmission within the same packet. This specification does not define or
use any contents of the Packet Header.
Forwarded messages MAY be jittered as described in ,
including the observation that the forwarding jitter of all messages received
in a single packet SHOULD be the same. The value of MAXJITTER used in jittering
a forwarded message MAY be based on information in that message (in particular
any Message TLVs with Type = INTERVAL_TIME or Type = VALIDITY_TIME) or otherwise
SHOULD be with a maximum delay of F_MAXJITTER. A router MAY modify the jitter
applied to a message in order to more efficiently combine messages in packets,
as long as the maximum jitter is not exceeded.
This specification defines two Message TLVs and four Address Block TLVs.
All references in this specification to TLVs that do not indicate a type extension
assume Type Extension = 0. TLVs in processed messages with a type
extension that is
neither zero as so assumed, nor a specifically indicated non-zero type extension, are ignored.
Note that, following and network byte order, bits in
an octet are
numbered
from 0 (most significant) to 7 (least significant).
The MPR_WILLING TLV is used in HELLO messages. A message MUST NOT contain more than one MPR_WILLING TLV.
TypeValue LengthValueMPR_WILLING1 octetBits 0-3 encode the parameter WILL_FLOODING; bits 4-7 encode the parameter WILL_ROUTING.
The CONT_SEQ_NUM TLV is used in TC messages. A message MUST NOT contain more than one CONT_SEQ_NUM TLV.
TypeValue LengthValueCONT_SEQ_NUM2 octetsThe ANSN contained in the Neighbor Information Base.
The LINK_METRIC TLV is used in HELLO messages and TC messages. It MAY
use any type extension; only LINK_METRIC TLVs with type extension equal
to LINK_METRIC_TYPE will be used by this specification. An address
MUST NOT be associated with more than one link metric value for any given
type extension, kind (link or neighbor), and direction using this TLV.
TypeValue LengthValueLINK_METRIC2 octetsBits 0-3 indicate kind(s) and direction(s); bits 4-7 indicate
exponent (b); and bits 8-15 indicate mantissa (a).
The exponent and mantissa use the representation defined in
. Each bit of the types and directions
sub-field, if set ('1'), indicates that the link metric is of the indicated
kind and direction. Any combination of these bits MAY be used.
BitKindDirection0Link metricIncoming1Link metricOutgoing2Neighbor metricIncoming3Neighbor metricOutgoing
The MPR TLV is used in HELLO messages and indicates that an address with
which it is associated is of a symmetric 1-hop neighbor that has been
selected as an MPR.
TypeValue LengthValueMPR1 octetFLOODING indicates that the corresponding address is of a neighbor
selected as a flooding MPR; ROUTING indicates that the corresponding
address is of a neighbor selected as a routing MPR; and FLOOD_ROUTE
indicates both (see ).
The NBR_ADDR_TYPE TLV is used in TC messages.
TypeValue LengthValueNBR_ADDR_TYPE1 octetORIGINATOR indicates that the corresponding address (which MUST have
maximum prefix length) is an originator address; ROUTABLE indicates
that the corresponding network address is a routable address of an
interface; and ROUTABLE_ORIG indicates that the corresponding address is
both (see ).
If an address is both an originator address and a routable address, then it
may be associated with either one Address Block TLV with Type := NBR_ADDR_TYPE
and Value := ROUTABLE_ORIG, or with two Address Block TLVs with Type:= NBR_ADDR_TYPE,
one with Value := ORIGINATOR and one with Value := ROUTABLE.
The GATEWAY TLV is used in TC messages. An address MUST NOT be associated with
more than one hop count value using this TLV.
TypeValue LengthValueGATEWAY1 octetNumber of hops to attached network.
All address objects included in a TC message according to this specification MUST
be associated either with at least one TLV with Type := NBR_ADDR_TYPE or with a TLV
with Type := GATEWAY, but not both. Any other address objects MAY be included in
Address Blocks in a TC message but are ignored by this specification.
This section describes the optimized flooding operation (MPR flooding) used
when control messages, as instances of , are intended
for MANET-wide distribution. This flooding mechanism defines when a received
message is, or is not, processed and/or forwarded.
This flooding mechanism is used by this protocol and MAY be used by extensions
to this protocol that define, and hence own, other Message Types, to manage
processing and/or forwarding of these messages. This specification contains
elements (P_type, RX_type, F_type) required only for such usage.
This flooding mechanism is always used for TC messages (see ).
Received HELLO messages (see ) are, unless invalid,
always processed and never forwarded by this flooding mechanism. They thus do not need
to be recorded in the Received Message Information Base.
The processing selection and forwarding mechanisms are designed to only need
to parse the Message Header in order to determine whether a message is to be
processed and/or forwarded and not to have to parse the Message Body even if
the message is forwarded (but not processed). An implementation MAY only parse
the Message Body if necessary or MAY always parse the Message Body and reject
the message if it cannot be so parsed or any other error is identified.
An implementation MUST discard the message silently if it is unable to
parse the Message Header or (if attempted) the Message Body, or if a message
(other than a HELLO message) does not include a message sequence number.
On receiving, on an OLSRv2 interface, a message of a type specified to be
using this mechanism, which includes the TC messages defined in this
specification, a router MUST perform the following:
If the router recognizes from the originator address of the message
that the message is one that the receiving router itself originated
(i.e., the message originator address is the originator address of this
router or is an O_orig_addr in an Originator Tuple), then the message
MUST be silently discarded.
Otherwise:
If the message is of a type that may be processed, then the message
is considered for processing according to
.
If the message is of a type that may be forwarded, AND:
<msg-hop-limit> is present and <msg-hop-limit>
> 1; AND<msg-hop-count> is not present or <msg-hop-count> < 255,
then the message is considered for forwarding according to
.
If a message (the "current message") is considered for processing,
then the following tasks MUST be performed:
If the sending address (i.e., the source address of the IP datagram
containing the current message) does not match (taking into account
any address prefix) a network address in an L_neighbor_iface_addr_list
of a Link Tuple, with L_status = SYMMETRIC, in the Link Set for the
OLSRv2 interface on which the current message was received (the
"receiving interface"), then processing the current message is OPTIONAL.
If the current message is not processed, then the following steps are
not carried out.
If a Processed Tuple exists with:
P_type = the Message Type of the current message; AND
P_orig_addr = the originator address of the current message; AND
P_seq_number = the message sequence number of the current message,
then the current message MUST NOT be processed.
Otherwise:
Create a Processed Tuple in the Processed Set with:
P_type := the Message Type of the current message;
P_orig_addr := the originator address of the current message;
P_seq_number := the sequence number of the current message;
P_time := current time + P_HOLD_TIME.
Process the current message according to its Message Type. For a TC
message, this is as defined in .
If a message (the "current message") is considered for forwarding,
then the following tasks MUST be performed:
If the sending address (i.e., the source address of the IP datagram
containing the current message) does not match (taking into account
any address prefix) a network address in an L_neighbor_iface_addr_list
of a Link Tuple, with L_status = SYMMETRIC, in the Link Set for the
OLSRv2 interface on which the current message was received (the
"receiving interface"), then the current message MUST be silently
discarded.
Otherwise:
If a Received Tuple exists in the Received Set for the receiving
interface, with:
RX_type = the Message Type of the current message; AND
RX_orig_addr = the originator address of the current message; AND
RX_seq_number = the sequence number of the current message,
then the current message MUST be silently discarded.
Otherwise:
Create a Received Tuple in the Received Set for the receiving
interface with:
RX_type := the Message Type of the current message;
RX_orig_addr := originator address of the current message;
RX_seq_number := sequence number of the current message;
RX_time := current time + RX_HOLD_TIME.
If a Forwarded Tuple exists with:
F_type = the Message Type of the current message; AND
F_orig_addr = the originator address of the current message; AND
F_seq_number = the sequence number of the current message,
then the current message MUST be silently discarded.
Otherwise, if the sending address matches (taking account
of any address prefix), any network address in an
L_neighbor_iface_addr_list of a Link Tuple in the Link
Set for the receiving OLSRv2 interface that has L_status
= SYMMETRIC and L_mpr_selector = true, then:
Create a Forwarded Tuple in the Forwarded Set with:
F_type := the Message Type of the current message;
F_orig_addr := originator address of the current message;
F_seq_number := sequence number of the current message;
F_time := current time + F_HOLD_TIME.
The Message Header of the current message is modified by:
Decrement <msg-hop-limit> in the Message Header by 1; AND
If present, increment <msg-hop-count> in the Message Header by 1.
The message is transmitted over all OLSRv2 interfaces, as described in
.
Otherwise, the current message MUST be silently discarded.
The HELLO Message Type is owned by NHDP , and
HELLO messages are thus generated, transmitted, received, and processed by
NHDP. This protocol, as permitted by ,
also uses HELLO messages, including adding to HELLO message generation and
implementing additional processing based on received HELLO messages. HELLO
messages are not forwarded by NHDP or by OLSRv2.
HELLO messages sent over OLSRv2 interfaces are generated as defined in
and then modified as described in this section. HELLO messages sent on other MANET interfaces
are not modified by this specification.
HELLO messages sent over OLSRv2 interfaces are extended by adding the following elements:
A message originator address, recording this router's originator address.
This MUST use a <msg-orig-addr> element, unless:
The message specifies only a single local interface address (i.e., contains
only one address object that is associated with an Address Block TLV with
Type = LOCAL_IF and that has no prefix length or a maximum prefix length)
that will then be used as the message originator address; OR
The message does not include any local interface network addresses (i.e.,
has no address objects associated with an Address Block TLV with Type = LOCAL_IF),
as permitted by the specification in , when the router
that generated the HELLO message has only one interface address and will use
that as the sending address of the IP datagram in which the HELLO message is
contained. In this case, that address will be used as the message originator
address.
A Message TLV with Type := MPR_WILLING MUST be included.
The following cases associate Address Block TLVs with one or more addresses from
a Link Tuple or a Neighbor Tuple if these are included in the HELLO message. In
each case, the TLV MUST be associated with at least one address object for an address
from the relevant Tuple; the TLV MAY be associated with more such addresses (including a
copy of that address object, possibly not itself associated with any other indicated
TLVs, in the same or a different Address Block). These additional TLVs MUST NOT be
associated with any other addresses in a HELLO message that will be
processed by NHDP
.
For each Link Tuple for which L_in_metric != UNKNOWN_METRIC and for which one or
more addresses in its L_neighbor_iface_addr_list are included as address objects
with an associated Address Block TLV with Type = LINK_STATUS and Value = HEARD
or Value = SYMMETRIC, at least one of these addresses MUST be associated
with an Address Block TLV with Type := LINK_METRIC indicating an incoming link
metric with value L_in_metric.
For each Link Tuple for which L_out_metric != UNKNOWN_METRIC and for which one or
more addresses in its L_neighbor_iface_addr_list are included as address objects
with an associated Address Block TLV with Type = LINK_STATUS and Value = SYMMETRIC,
at least one of these addresses MUST be associated with an Address Block TLV with
Type := LINK_METRIC indicating an outgoing link metric with value L_out_metric.
For each Neighbor Tuple for which N_symmetric = true and for which one or
more addresses in its N_neighbor_addr_list are included as address objects
with an associated Address Block TLV with Type = LINK_STATUS or Type = OTHER_NEIGHB
and Value = SYMMETRIC, at least one of these addresses MUST be associated with an
Address Block TLV with Type := LINK_METRIC indicating an incoming neighbor metric
with value N_in_metric.
For each Neighbor Tuple for which N_symmetric = true and for which one or
more addresses in its N_neighbor_addr_list are included as address objects
with an associated Address Block TLV with Type = LINK_STATUS or Type = OTHER_NEIGHB
and Value = SYMMETRIC, at least one of these addresses MUST be associated with an
Address Block TLV with Type := LINK_METRIC indicating an outgoing neighbor metric
with value N_out_metric.
For each Neighbor Tuple with N_flooding_mpr = true and for which one or more
network addresses in its N_neighbor_addr_list are included as address objects
in the HELLO message with an associated Address Block TLV with Type = LINK_STATUS
and Value = SYMMETRIC, at least one of these addresses MUST be associated
with an Address Block TLV with Type := MPR and Value := FLOODING or
Value := FLOOD_ROUTE.
For each Neighbor Tuple with N_routing_mpr = true and for which one or more
network addresses in its N_neighbor_addr_list are included as address objects
in the HELLO message with an associated Address Block TLV with Type = LINK_STATUS
and Value = SYMMETRIC, at least one of these addresses MUST be associated
with an Address Block TLV with Type := MPR and Value := ROUTING or
Value := FLOOD_ROUTE.
HELLO messages are scheduled and transmitted by NHDP .
This protocol MAY require that an additional HELLO message be sent on each
OLSRv2 interface when either of the router's sets of MPRs changes, in
addition to the cases specified in and subject
to the constraints specified in (notably on
minimum HELLO message transmission intervals).
When received on an OLSRv2 interface, HELLO messages are made available
to this protocol in two ways, both as permitted by :
Such received HELLO messages MUST be made available to this protocol
on reception, which allows them to be discarded before being
processed by NHDP
, for example, if the information added to the
HELLO message by this specification is inconsistent.
Such received HELLO messages MUST be made available to OLSRv2 after NHDP
has completed its processing thereof, unless
discarded as malformed by NHDP, for processing by OLSRv2.
In addition to the reasons specified in for
discarding a HELLO message on reception, a HELLO message received on an
OLSRv2 interface MUST be discarded before processing by NHDP
or this
specification if it:
Has more than one Message TLV with Type = MPR_WILLING.
Has a message originator address, or a network address corresponding to an
address object associated with an Address Block TLV with Type = LOCAL_IF,
that is partially owned by this router. (Some of these cases are already
excluded by .)
Includes any address object associated with an Address Block TLV with
Type = LINK_STATUS or Type = OTHER_NEIGHB that overlaps the message's
originator address.
Contains any address that will be processed by NHDP
that is associated, using the same or different address objects, with
two different values of link metric with the same kind and direction
using a TLV with Type = LINK_METRIC and Type Extension = LINK_METRIC_TYPE.
This also applies to different addresses that are both of the OLSRv2
interface on which the HELLO message was received.
Contains any address object associated with an Address Block TLV with
Type = MPR that is not also associated with an Address Block TLV with
Type = LINK_STATUS and Value = SYMMETRIC (including using a different
copy of that address object in the same or a different Address Block).
HELLO messages are first processed as specified in .
That processing includes identifying (or creating) a Link Tuple and a Neighbor Tuple
corresponding to the originator of the HELLO message (the "current Link Tuple"
and the "current Neighbor Tuple"). After this, the following processing MUST also be
performed if the HELLO message is received on an OLSRv2 interface and contains a TLV
with Type = MPR_WILLING:
If the HELLO message has a well-defined message originator address, i.e.,
has an <msg-orig-addr> element or has zero or one network addresses
associated with a TLV with Type = LOCAL_IF:
Remove any Neighbor Tuple, other than the current Neighbor Tuple, with
N_orig_addr = message originator address, taking any consequent action
(including removing one or more Link Tuples) as specified in
.
The current Link Tuple is then updated according to:
Update L_in_metric and L_out_metric as described in ;
Update L_mpr_selector as described in .
The current Neighbor Tuple is then updated according to:
N_orig_addr := message originator address;
Update N_in_metric and N_out_metric as described in ;
Update N_will_flooding and N_will_routing as described in ;
Update N_mpr_selector as described in .
All 2-Hop Tuples that were updated as described in
are then updated according to:
Update N2_in_metric and N2_out_metric as described in
.
If there are any changes to the router's Information Bases, then perform the processing defined in
.
For each address in a received HELLO message with an associated TLV
with Type = LINK_STATUS and Value = HEARD or Value = SYMMETRIC, an
incoming (to the message originator) link metric value is defined.
If the HELLO message contains a TLV with Type = LINK_METRIC and Type
Extension = LINK_METRIC_TYPE that associates that address value with a
metric value of the appropriate kind
(link) and direction (incoming) of metric, then the incoming link metric
is that metric value; otherwise, the incoming link metric is defined as UNKNOWN_METRIC.
For each address in a received HELLO message with an associated TLV
with Type = LINK_STATUS and Value = SYMMETRIC, an outgoing (from the
message originator) link metric value is defined.
If the HELLO message contains a TLV with Type = LINK_METRIC and Type
Extension = LINK_METRIC_TYPE that associates that address value with
a metric value of the appropriate kind (link) and direction
(outgoing) of metric, then the outgoing link metric is that metric
value; otherwise, the outgoing link metric is defined as
UNKNOWN_METRIC.
For each address in a received HELLO message with an associated TLV
with Type = LINK_STATUS or Type = OTHER_NEIGHB and Value = SYMMETRIC,
an incoming (to the message originator) neighbor metric value is
defined.
If the HELLO message contains a TLV with Type = LINK_METRIC and Type
Extension = LINK_METRIC_TYPE that associates that address value with
a metric value of the appropriate kind (neighbor) and direction
(incoming) of metric, then the incoming neighbor metric is that metric
value; otherwise, the incoming neighbor metric is defined as
UNKNOWN_METRIC.
For each address in a received HELLO message with an associated TLV
with Type = LINK_STATUS or Type = OTHER_NEIGHB and Value = SYMMETRIC,
an outgoing (from the message originator) neighbor metric value is
defined.
If the HELLO message contains a TLV with Type = LINK_METRIC and Type
Extension = LINK_METRIC_TYPE that associates that address value with
a metric value of the appropriate kind (neighbor) and direction
(outgoing) of metric, then the outgoing neighbor metric is that metric
value; otherwise, the outgoing neighbor metric is defined as
UNKNOWN_METRIC.
The link metric elements L_in_metric and L_out_metric in a Link Tuple
are updated according to the following:
For any Link Tuple, L_in_metric MAY be set to any representable value
by a process outside this specification at any time. L_in_metric MUST
be so set whenever L_status becomes equal to HEARD or SYMMETRIC (if no
other value is available, then the value MAXIMUM_METRIC MUST be used).
Setting L_in_metric MAY use information based on the receipt of a packet
including a HELLO message that causes the creation or updating of the
Link Tuple.
When, as specified in , a Link Tuple is updated
(possibly immediately after being created) due to the receipt of a HELLO
message, if L_status = SYMMETRIC, then L_out_metric is set equal to the
incoming link metric for any included address of the interface on which
the HELLO message was received. (Note that the rules for discarding
HELLO messages in make this value
unambiguous.)
If there is any such address, but no such link
metric, then L_out_metric is set to UNKNOWN_METRIC.
The neighbor metric elements N_in_metric and N_out_metric in a Neighbor Tuple
are updated according to .
The metric elements N2_in_metric and N2_out_metric in any 2-Hop Tuple
updated as defined in are updated to equal the
incoming neighbor metric and outgoing neighbor metric, respectively,
associated with the corresponding N2_2hop_addr. If there are no such metrics,
then these elements are set to UNKNOWN_METRIC.
N_will_flooding and N_will_routing in the current Neighbor Tuple are updated
using the Message TLV with Type = MPR_WILLING (note that this must be present)
as follows:
N_will_flooding := bits 0-3 of the value of that TLV; AND
N_will_routing := bits 4-7 of the value of that TLV.
(Each being in the range 0 to 15, i.e., WILL_NEVER to WILL_ALWAYS.)
L_mpr_selector is updated as follows:
If a router finds an address object representing any of its relevant local
interface network addresses (i.e., those contained in the I_local_iface_addr_list of
an OLSRv2 interface) with an associated Address Block TLV with Type = MPR and
Value = FLOODING or Value = FLOOD_ROUTE in the HELLO message (indicating that
the originating router has selected the receiving router as a flooding MPR),
then, for the current Link Tuple:
L_mpr_selector := true.
Otherwise (i.e., if no such address object and Address Block TLV was found),
if a router finds an address object representing any of its relevant local
interface network addresses (i.e., those contained in the I_local_iface_addr_list of
an OLSRv2 interface) with an associated Address Block TLV with Type = LINK_STATUS
and Value = SYMMETRIC in the HELLO message, then, for the current Link Tuple:
L_mpr_selector := false.
N_mpr_selector is updated as follows:
If a router finds an address object representing any of its relevant local
interface network addresses (those contained in the I_local_iface_addr_list of
an OLSRv2 interface) with an associated Address Block TLV with Type = MPR and
Value = ROUTING or Value = FLOOD_ROUTE in the HELLO message (indicating that
the originating router has selected the receiving router as a routing MPR), then,
for the current Neighbor Tuple:
N_mpr_selector := true;
N_advertised := true.
Otherwise (i.e., if no such address object and Address Block TLV was found),
if a router finds an address object representing any of its relevant local
interface network addresses (those contained in the I_local_iface_addr_list of
an OLSRv2 interface) with an associated Address Block TLV with Type = LINK_STATUS
and Value = SYMMETRIC in the HELLO message, then, for the current Neighbor Tuple:
N_mpr_selector := false;
The router MAY also set N_advertised := false.
This protocol defines, and hence owns, the TC Message Type (see ).
Thus, as specified in , this protocol generates and transmits
all TC messages, receives all TC messages, and is responsible for determining whether
and how each TC message is to be processed (updating the Topology Information Base)
and/or forwarded, according to this specification.
A TC message is a message as defined in . A generated TC
message MUST contain the following elements as defined in :
A message originator address, recording this router's originator address.
This MUST use a <msg-orig-addr> element.
<msg-seq-num> element containing the message sequence number.
A <msg-hop-limit> element, containing TC_HOP_LIMIT. A router MAY use
the same or different values of TC_HOP_LIMIT in its TC messages (see
).
A <msg-hop-count> element, containing zero, if the message contains a TLV
with either Type = VALIDITY_TIME or Type = INTERVAL_TIME (as specified in
) indicating more than one time value according to
distance. A TC message MAY contain such a <msg-hop-count> element even
if it does not need to.
A single Message TLV with Type := CONT_SEQ_NUM and Value := ANSN from the
Neighbor Information Base. If the TC message is complete, then this Message
TLV MUST have Type Extension := COMPLETE; otherwise, it MUST have
Type Extension := INCOMPLETE. (Exception: a TC message MAY omit such a
Message TLV if the TC message does not include any address objects with
an associated Address Block TLV with Type = NBR_ADDR_TYPE or Type = GATEWAY.)
A single Message TLV with Type := VALIDITY_TIME, as specified in
. If all TC messages are sent with the same hop limit,
then this TLV MUST have a value encoding the period T_HOLD_TIME. If TC messages
are sent with different hop limits (more than one value of TC_HOP_LIMIT), then
this TLV MUST specify times that vary with the number of hops
appropriate to the chosen pattern of TC message hop limits, as specified in
; these times SHOULD be appropriate multiples of
T_HOLD_TIME. The options included in for representing
zero and infinite times MUST NOT be used.
If the TC message is complete, all network addresses that are the N_orig_addr
of a Neighbor Tuple with N_advertised = true, MUST be represented by address
objects in one or more Address Blocks. If the TC message is incomplete, then
any such address objects MAY be included. At least one copy of each such
address object that is included MUST be associated with an Address Block TLV
with Type := NBR_ADDR_TYPE and Value := ORIGINATOR or with Value := ROUTABLE_ORIG
if that address object is also to be associated with Value = ROUTABLE.
If the TC message is complete, all routable addresses that are in the
N_neighbor_addr_list of a Neighbor Tuple with N_advertised = true MUST
be represented by address objects in one or more Address Blocks. If the
TC message is incomplete, then any such address objects MAY be included.
At least one copy of each such address object MUST be associated with an
Address Block TLV with Type = NBR_ADDR_TYPE and Value = ROUTABLE or
with Value = ROUTABLE_ORIG if also to be associated with Value = ORIGINATOR.
At least one copy of each such address object MUST be associated with an
Address Block TLV with Type = LINK_METRIC and Type Extension = LINK_METRIC_TYPE
indicating an outgoing neighbor metric with value equal to the corresponding
N_out_metric.
If the TC message is complete, all network addresses that are the AL_net_addr
of a Local Attached Network Tuple MUST be represented by address objects in one
or more Address Blocks. If the TC message is incomplete, then any such address
objects MAY be included. At least one copy of each such address object MUST be
associated with an Address Block TLV with Type := GATEWAY and Value := AN_dist.
At least one copy of each such address object MUST be associated with an
Address Block TLV with Type = LINK_METRIC and Type Extension = LINK_METRIC_TYPE
indicating an outgoing neighbor metric equal to the corresponding AL_metric.
A TC message MAY contain:
A single Message TLV with Type := INTERVAL_TIME, as specified in .
If all TC messages are sent with the same hop limit, then this TLV MUST have a value
encoding the period TC_INTERVAL. If TC messages are sent with different hop limits,
then this TLV MUST specify times that vary with the number of hops appropriate
to the chosen pattern of TC message hop limits, as specified in ;
these times MUST be appropriate multiples of TC_INTERVAL. The options included in
for representing zero and infinite times MUST NOT be used.
A router with one or more OLSRv2 interfaces, and with any Neighbor Tuples
with N_advertised = true, or with a non-empty Local Attached Network Set
MUST generate TC messages. A router that does not have such information
to advertise MUST also generate "empty" TC messages for a period A_HOLD_TIME
after it last generated a non-empty TC message.
Complete TC messages are generated and transmitted periodically on all
OLSRv2 interfaces, with a default interval between two consecutive
TC message transmissions by the same router of TC_INTERVAL.
TC messages MAY be generated in response to a change in the information
that they are to advertise, indicated by a change in the ANSN in the
Neighbor Information Base. In this case, a router MAY send a complete
TC message and, if so, MAY restart its TC message schedule. Alternatively,
a router MAY send an incomplete TC message with at least the newly
advertised network addresses (i.e., not previously, but now, an N_orig_addr
or in an N_neighbor_addr_list in a Neighbor Tuple with N_advertised = true
or an AL_net_addr) in its Address Blocks, with associated Address Block TLV(s).
Note that a router cannot report removal of advertised content using an
incomplete TC message.
When sending a TC message in response to a change of advertised network addresses,
a router MUST respect a minimum interval of TC_MIN_INTERVAL between sending
TC messages (complete or incomplete) and a maximum interval of TC_INTERVAL
between sending complete TC messages. Thus, a router MUST NOT send an incomplete
TC message if within TC_MIN_INTERVAL of the next scheduled time to send a complete
TC message.
The generation of TC messages, whether scheduled or triggered by a change of
contents, MAY be jittered as described in . The values
of MAXJITTER used MUST be:
TP_MAXJITTER for periodic TC message generation;TT_MAXJITTER for responsive TC message generation.
On receiving a TC message on an OLSRv2 interface, the receiving router MUST then
follow the processing and forwarding procedures defined in
.
If the message is considered for processing (),
then a router MUST first check if the message is invalid for processing by this router,
as defined in .
A router MAY make a
similar check before considering a message for forwarding; it MUST
check the aspects that apply to elements in the Message Header.
If the TC message is not invalid, then the processing specific to TC Message Type,
described in , MUST be applied. This will
update its appropriate Interface Information Bases and its Router Information Base.
Following this, if there are any changes in these Information Bases, then the
processing in MUST be performed.
A received TC message is invalid for processing by this router if the message:
Has an address length specified in the Message Header that is not equal
to the length of the addresses used by this router.
Does not include a message originator address and a message sequence number.
Does not include a hop count and contains a multi-value TLV with
Type = VALIDITY_TIME or Type = INTERVAL_TIME, as defined in
.
Does not have exactly one Message TLV with Type = VALIDITY_TIME.
Has more than one Message TLV with Type = INTERVAL_TIME.
Does not have a Message TLV with Type = CONT_SEQ_NUM and
Type Extension = COMPLETE or Type Extension = INCOMPLETE and contains
at least one address object associated with an Address Block TLV with
Type = NBR_ADDR_TYPE or Type = GATEWAY.
Has more than one Message TLV with Type = CONT_SEQ_NUM and
Type Extension = COMPLETE or Type Extension = INCOMPLETE.
Has a message originator address that is partially owned by this router.
Includes any address object with a prefix length that is not maximal
(equal to the address length, in bits), associated with an Address Block TLV
with Type = NBR_ADDR_TYPE and Value = ORIGINATOR or Value = ROUTABLE_ORIG.
Includes any address object that represents a non-routable address,
associated with an Address Block TLV with Type = NBR_ADDR_TYPE and
Value = ROUTABLE or Value = ROUTABLE_ORIG.
Includes any address object associated with an Address Block TLV with
Type = NBR_ADDR_TYPE or Type = GATEWAY that also represents the message's
originator address.
Includes any address object (including different copies of an address
object in the same or different Address Blocks) that is associated with
an Address Block TLV with Type = NBR_ADDR_TYPE or Type = GATEWAY that
is also associated with more than one outgoing neighbor metric using a
TLV with Type = LINK_METRIC and Type Extension = LINK_METRIC_TYPE.
Associates any address object (including different copies of an address
object in the same or different Address Blocks) with more than one
single hop count value using one or more Address Block TLV(s) with
Type = GATEWAY.
Associates any address object (including different copies of an address
object in the same or different Address Blocks) with Address Block
TLVs with Type = NBR_ADDR_TYPE and Type = GATEWAY.
A router MAY recognize additional reasons for identifying that a message
is invalid. An invalid message MUST be silently discarded, without updating
the router's Information Bases.
Note that a router that acts inconsistently, for example, rejecting TC
messages "at random", may cause parts of the network to not be able to
communicate with other parts of the network. It is RECOMMENDED that
such "additional reasons for identifying that a message is invalid"
be a consistent network-wide policy (e.g., as part of a security policy),
implemented on all participating routers.
When, according to , a TC message is to be
"processed according to its type", this means that:
If the TC message contains a Message TLV with Type = CONT_SEQ_NUM and
Type Extension = COMPLETE, then processing according to
and then according to is carried out.
If the TC message contains a Message TLV with Type = CONT_SEQ_NUM and
Type Extension = INCOMPLETE, then only processing according to
is carried out.
For the purposes of the TC message processing in and :
"validity time" is calculated from a VALIDITY_TIME Message TLV in the TC message according
to the specification in . All information in the TC message
has the same validity time.
"received ANSN" is defined as being the value of a Message TLV with Type = CONT_SEQ_NUM.
"associated metric value" is defined for any address in the TC message as being either
the outgoing neighbor metric value indicated by a TLV with Type = LINK_METRIC and
Type Extension = LINK_METRIC_TYPE that is associated with any address object in the
TC message that is equal to that address or as UNKNOWN_METRIC otherwise. (Note that
the rules in make this definition unambiguous.)
Comparisons of sequence numbers are carried out as specified in .
The TC message is processed as follows:
The Advertising Remote Router Set is updated according to .
If the TC message is indicated as discarded in that processing, then the following steps
are not carried out.
The Router Topology Set is updated according to .
The Routable Address Topology Set is updated according to .
The Attached Network Set is updated according to .
The router MUST update its Advertising Remote Router Set as follows:
If there is an Advertising Remote Router Tuple with:
AR_orig_addr = message originator address; ANDAR_seq_number > received ANSN,
then the TC message MUST be discarded.
Otherwise:
If there is no Advertising Remote Router Tuple such that:
AR_orig_addr = message originator address;
then create an Advertising Remote Router Tuple with:
AR_orig_addr := message originator address.
This Advertising Remote Router Tuple (existing or new)
is then modified as follows:
AR_seq_number := received ANSN;AR_time := current time + validity time.
The router MUST update its Router Topology Set as follows:
For each address (henceforth, advertised address) that
corresponds to one
or more address objects with an associated Address Block TLV with
Type = NBR_ADDR_TYPE and Value = ORIGINATOR or Value = ROUTABLE_ORIG
and that is not partially owned by this router, perform the following
processing:
If the associated metric is UNKNOWN_METRIC, then remove any
Router Topology Tuple such that:
TR_from_orig_addr = message originator address; ANDTR_to_orig_addr = advertised address.
Otherwise, if there is no Router Topology Tuple such that:
TR_from_orig_addr = message originator address; ANDTR_to_orig_addr = advertised address,
then create a new Router Topology Tuple with:
TR_from_orig_addr := message originator address;TR_to_orig_addr := advertised address.
This Router Topology Tuple (existing or new) is then modified as follows:
TR_seq_number := received ANSN;TR_metric := associated link metric;TR_time := current time + validity time.
The router MUST update its Routable Address Topology Set as follows:
For each network address (henceforth, advertised address) that corresponds to
one or more address objects with an associated Address Block TLV with
Type = NBR_ADDR_TYPE and Value = ROUTABLE or Value = ROUTABLE_ORIG
and that is not partially owned by this router, perform the following
processing:
If the associated metric is UNKNOWN_METRIC, then remove any
Routable Address Topology Tuple such that:
TA_from_orig_addr = message originator address; ANDTA_dest_addr = advertised address.
Otherwise, if there is no Routable Address Topology Tuple such that:
TA_from_orig_addr = message originator address; ANDTA_dest_addr = advertised address,
then create a new Routable Address Topology Tuple with:
TA_from_orig_addr := message originator address;TA_dest_addr := advertised address.
This Routable Address Topology Tuple (existing or new) is then modified as follows:
TA_seq_number := received ANSN;TA_metric := associated link metric;TA_time := current time + validity time.
The router MUST update its Attached Network Set as follows:
For each network address (henceforth, attached address) that corresponds to one or more
address objects with an associated Address Block TLV with Type = GATEWAY and that
is not fully owned by this router, perform the following processing:
If the associated metric is UNKNOWN_METRIC, then remove any
Attached Network Tuple such that:
AN_net_addr = attached address; ANDAN_orig_addr = message originator address.
Otherwise, if there is no Attached Network Tuple such that:
AN_net_addr = attached address; ANDAN_orig_addr = message originator address,
then create a new Attached Network Tuple with:
AN_net_addr := attached address;AN_orig_addr := message originator address.
This Attached Network Tuple (existing or new) is then modified as follows:
AN_seq_number := received ANSN;AN_dist := the Value of the associated GATEWAY TLV;AN_metric := associated link metric;AN_time := current time + validity time.
The TC message is processed as follows:
The Router Topology Set is updated according to .
The Routable Address Topology Set is updated according to .
The Attached Network Set is updated according to .
The Router Topology Set MUST be updated as follows:
Any Router Topology Tuples with:
TR_from_orig_addr = message originator address; ANDTR_seq_number < received ANSN,
MUST be removed.
The Routable Address Topology Set MUST be updated as follows:
Any Routable Address Topology Tuples with:
TA_from_orig_addr = message originator address; ANDTA_seq_number < received ANSN,
MUST be removed.
The Attached Network Set MUST be updated as follows:
Any Attached Network Tuples with:
AN_orig_addr = message originator address; ANDAN_seq_number < received ANSN,
MUST be removed.
The changes described in the following sections MUST be carried
out when any Information Base changes as indicated.
If the router changes its originator address, then:
If there is no Originator Tuple with:
O_orig_addr = old originator address
then create an Originator Tuple with:
O_orig_addr := old originator address
The Originator Tuple (existing or new) with:
O_orig_addr = new originator address
is then modified as follows:
O_time := current time + O_HOLD_TIME
The consistency of a Link Tuple MUST be maintained according to the following rules,
in addition to those in :
If L_status = HEARD or L_status = SYMMETRIC, then L_in_metric MUST be
set (by a process outside this specification).
If L_status != SYMMETRIC, then set L_mpr_selector := false.
If L_out_metric = UNKNOWN_METRIC, then L_status MUST NOT equal SYMMETRIC;
set L_SYM_time := EXPIRED if this would otherwise be the case.
The consistency of a Neighbor Tuple MUST be maintained according to the following rules,
in addition to those in :
If N_symmetric = true, then N_in_metric MUST equal the minimum value of all
L_in_metric of corresponding Link Tuples with L_status = SYMMETRIC and
L_in_metric != UNKNOWN_METRIC. If there are no such Link Tuples, then
N_in_metric MUST equal UNKNOWN_METRIC.
If N_symmetric = true, then N_out_metric MUST equal the minimum value of all
L_out_metric of corresponding Link Tuples with L_status = SYMMETRIC and
L_out_metric != UNKNOWN_METRIC. If there are no such Link Tuples, then
N_out_metric MUST equal UNKNOWN_METRIC.
If N_symmetric = false, then N_flooding_mpr, N_routing_mpr, N_mpr_selector, and
N_advertised MUST all be equal to false.
If N_mpr_selector = true, then N_advertised MUST be equal to true.
If N_symmetric = true, N_out_metric != UNKNOWN_METRIC and
N_mpr_selector = false, then a router MAY select N_advertised =
true or N_advertised = false. The more neighbors that are
advertised, the larger TC messages become, but the more
redundancy is available for routing. A router SHOULD consider
the nature of its network in making such a decision and SHOULD
avoid unnecessary changes in advertising status, which may result
in unnecessary changes to routing.
The router MUST increment the ANSN in the Neighbor Information Base whenever:
Any Neighbor Tuple changes its N_advertised value, or any Neighbor Tuple with
N_advertised = true is removed.
Any Neighbor Tuple with N_advertised = true changes its
N_orig_addr or has any routable address added to or removed
from N_neighbor_addr_list.
Any Neighbor Tuple with N_advertised = true has N_out_metric changed.
There is any change to the Local Attached Network Set.
The Router Topology Set, the Routable Address Topology Set, and the
Attached Network Set MUST be changed when an Advertising Remote Router Tuple
expires (AR_time is reached). The following changes are required before the
Advertising Remote Router Tuple is removed:
All Router Topology Tuples with:
TR_from_orig_addr = AR_orig_addr of the Advertising Remote Router Tuple
are removed.
All Routable Address Topology Tuples with:
TA_from_orig_addr = AR_orig_addr of the Advertising Remote Router Tuple
are removed.
All Attached Network Tuples with:
AN_orig_addr = AR_orig_addr of the Advertising Remote Router Tuple
are removed.
The sets of symmetric 1-hop neighbors selected as flooding MPRs and routing MPRs
MUST satisfy the conditions defined in .
To ensure this:
The set of flooding MPRs of a router MUST be recalculated if:
A Link Tuple is added with L_status = SYMMETRIC and
L_out_metric != UNKNOWN_METRIC; OR
A Link Tuple with L_status = SYMMETRIC and
L_out_metric != UNKNOWN_METRIC is removed; OR
A Link Tuple with L_status = SYMMETRIC and L_out_metric != UNKNOWN_METRIC
changes to having L_status = HEARD, L_status = LOST, or
L_out_metric = UNKNOWN_METRIC; OR
A Link Tuple with L_status = HEARD or L_status = LOST
changes to having L_status = SYMMETRIC and
L_out_metric != UNKNOWN_METRIC; OR
The flooding MPR selection process uses metric values (see
) and the L_out_metric of any
Link Tuple with L_status = SYMMETRIC changes; OR
The N_will_flooding of a Neighbor Tuple with N_symmetric = true
and N_out_metric != UNKNOWN_METRIC changes from WILL_NEVER
to any other value; OR
The N_will_flooding of a Neighbor Tuple with N_flooding_mpr = true
changes to WILL_NEVER from any other value; OR
The N_will_flooding of a Neighbor Tuple with N_symmetric = true,
N_out_metric != UNKNOWN_METRIC, and N_flooding_mpr = false
changes to WILL_ALWAYS from any other value; OR
A 2-Hop Tuple with N2_out_metric != UNKNOWN_METRIC
is added or removed; OR
The N2_out_metric of any 2-Hop Tuple changes and either
the flooding MPR selection process uses metric values (see
) or the change is to or from UNKNOWN_METRIC.
Otherwise, the set of flooding MPRs of a router MAY be recalculated if the
N_will_flooding of a Neighbor Tuple with N_symmetric = true
changes in any other way; it SHOULD be recalculated if N_flooding_mpr = false
and this is an increase in N_will_flooding or if N_flooding_mpr = true and
this is a decrease in N_will_flooding.
The set of routing MPRs of a router MUST be recalculated if:
A Neighbor Tuple is added with N_symmetric = true and
N_in_metric != UNKNOWN_METRIC; OR
A Neighbor Tuple with N_symmetric = true and N_in_metric != UNKNOWN_METRIC
is removed; OR
A Neighbor Tuple with N_symmetric = true and N_in_metric != UNKNOWN_METRIC
changes to having N_symmetric = false; OR
A Neighbor Tuple with N_symmetric = false changes to having
N_symmetric = true and N_in_metric != UNKNOWN_METRIC; OR
The N_in_metric of any Neighbor Tuple with N_symmetric = true changes; OR
The N_will_routing of a Neighbor Tuple with N_symmetric = true
and N_in_metric != UNKNOWN_METRIC changes from WILL_NEVER
to any other value; OR
The N_will_routing of a Neighbor Tuple with N_routing_mpr = true changes
to WILL_NEVER from any other value; OR
The N_will_routing of a Neighbor Tuple with N_symmetric = true,
N_in_metric != UNKNOWN_METRIC and N_routing_mpr = false
changes to WILL_ALWAYS from any other value; OR
A 2-Hop Tuple with N2_in_metric != UNKNOWN_METRIC is added or removed; OR
The N2_in_metric of any 2-Hop Tuple changes.
Otherwise, the set of routing MPRs of a router MAY be recalculated if the
N_will_routing of a Neighbor Tuple with N_symmetric = true
changes in any other way; it SHOULD be recalculated if N_routing_mpr = false
and this is an increase in N_will_routing or if N_routing_mpr = true and
this is a decrease in N_will_routing.
If either set of MPRs of a router is recalculated, this MUST be as described in
.
The Routing Set MUST be updated, as described in ,
when changes in the Local Information Base, the Neighborhood Information Base,
or the Topology Information Base indicate a change (including of any potentially
used outgoing neighbor metric values) of the known symmetric links and/or
attached networks in the MANET, hence changing the Topology Graph. It is sufficient
to consider only changes that affect at least one of:
The Local Interface Set for an OLSRv2 interface, if the change removes any
network address in an I_local_iface_addr_list. In this case, unless the
OLSRv2 interface is removed, it may not be necessary to do more than
replace such network addresses, if used, by an alternative network address
from the same I_local_iface_addr_list.
The Local Attached Set, if the change removes any
AL_net_addr that is also an AN_net_addr. In this case, it
may not be necessary to do more than add Routing Tuples
with R_dest_addr equal to that AN_net_addr.
The Link Set of any OLSRv2 interface, considering only Link Tuples that have,
or just had, L_status = SYMMETRIC and L_out_metric != UNKNOWN_METRIC
(including removal of such Link Tuples).
The Neighbor Set of the router, considering only Neighbor Tuples that have,
or just had, N_symmetric = true and N_out_metric != UNKNOWN_METRIC and do not
have N_orig_addr = unknown.
The 2-Hop Set of any OLSRv2 interface, if used in the creation
of the Routing Set and if the change affects any 2-Hop Tuples with
N2_out_metric != UNKNOWN_METRIC.
The Router Topology Set of the router.
The Routable Address Topology Set of the router.
The Attached Network Set of the router.
Each router MUST select, from among its willing symmetric 1-hop neighbors,
two subsets of these routers, as flooding and routing MPRs. This selection
is recorded in the router's Neighbor Set and reported in the router's
HELLO messages. Routers MAY select their MPRs by any process that satisfies
the conditions that follow, which may, but need not, use the organization
of the data described. Routers can freely interoperate whether they use the
same or different MPR selection algorithms.
Only flooding MPRs forward control messages flooded through the MANET,
thus effecting a flooding reduction, an optimization of the
flooding mechanism, known as MPR flooding. Routing MPRs are used to
effect a topology reduction in the MANET. (If no such reduction is
required, then a router can select all of its relevant neighbors as
routing MPRs.) Consequently, while it is not essential that these two
sets of MPRs are minimal, keeping the numbers of MPRs small ensures
that the overhead of this protocol is kept to a minimum.
MPRs are selected according to the following steps, defined in the
following sections:
A data structure known as a Neighbor Graph is defined.
The properties of an MPR Set derived from a Neighbor Graph
are defined. Any algorithm that creates an MPR Set that
satisfies these properties is a valid MPR selection algorithm.
An example algorithm that creates such an MPR Set is given in
.
How to create a Neighbor Graph for each interface based on
the corresponding Interface Information Base is defined, and
how to combine the resulting MPR Sets to determine the router's
flooding MPRs and record those in the router's Neighbor Set are described.
How to create a single Neighbor Graph based on all Interface
Information Bases and the Neighbor Information Base is defined,
and how to record the resulting MPR Set as the router's routing
MPRs in the router's Neighbor Set is described.
A specification as to when MPRs MUST be calculated is given.
When a router selects its MPRs, it MAY consider any characteristics
of its neighbors that it is aware of. In particular, it SHOULD consider the
willingness of the neighbor, as recorded by the corresponding N_will_flooding
or N_will_routing value, as appropriate, preferring neighbors with higher
values. (Note that willingness values equal to WILL_NEVER and WILL_ALWAYS
are always considered, as described.) However, a router MAY consider other
characteristics to have a greater significance.
Each router MAY select its flooding and routing MPRs independently
of each other or coordinate its selections. A router MAY make its
MPR selections independently of the MPR selection by other routers,
or it MAY, for example, give preference to routers that either are,
or are not, already selected as MPRs by other routers.
A Neighbor Graph is a structure defined here as consisting of sets N1 and
N2 and some associated metric and willingness values. Elements of set N1
represent willing symmetric 1-hop neighbors, and elements of set N2 represent
addresses of a symmetric 2-hop neighbor.
A Neighbor Graph has the following properties:
It contains two disjoint sets N1 and N2.
For each element x in N1, there is an associated willingness value W(x)
such that WILL_NEVER < W(x) <= WILL_ALWAYS.
For each element x in N1, there is an associated metric d1(x) > 0.
For some elements y in N2, there is an associated metric d1(y) > 0.
(Other elements y in N2 have undefined d1(y); this may be considered
to be infinite.)
For each element x in N1, there is a subset N2(x) of elements of N2;
this subset may be empty. For each x in N1 and each y in N2(x), there
is an associated metric d2(x,y) > 0. (For other x in N1 and y in N2,
d2(x,y) is undefined and may be considered infinite.)
N2 is equal to the union of all the N2(x) for all x in N1, i.e.,
for each y in N2, there is at least one x in N1 such that y is
in N2(x).
It is convenient to also define:
For each y in N2, the set N1(y) that contains x in N1 if and only if
y is in N2(x). From the final property above, N1(y) is not empty.
For each x in N1 and y in N2, if d2(x,y) is defined, then
d(x,y) := d1(x)+d2(x,y); otherwise, d(x,y) is not defined.
(Thus, d(x,y) is defined if y is in N2(x) or, equivalently,
if x is in N1(y).)
For any subset S of N1 and for each y in N2, the metric d(y,S) is the
minimum value of d1(y), if defined, and of all d(x,y) for x in
N1(y) and in S. If there are no such metrics to take the minimum value
of, then d(y,S) is undefined (may be considered to be infinite). From
the final property above, d(y,N1) is defined for all y.
Given a Neighbor Graph as defined in ,
an MPR Set for that Neighbor Graph is a subset M of the set N1 that
satisfies the following properties:
If x in N1 has W(x) = WILL_ALWAYS, then x is in M.
For any y in N2 that does not have a defined d1(y), there is at
least one element in M that is also in N1(y). This is
equivalent to the requirement that d(y,M) is defined.
For any y in N2, d(y,M) = d(y,N1).
These properties reflect that the MPR Set consists of
a set of symmetric 1-hop neighbors that cover all the symmetric 2-hop
neighbors and that they do so retaining a minimum distance
route (1-hop, if present, or 2-hop) to each symmetric 2-hop neighbor.
Note that if M is an MPR Set, then so is any subset of N1 that contains
M; also note that N1 is always an MPR Set. An MPR Set may be empty but
cannot be empty if N2 contains any elements y that do not have a defined
d1(y).
Whenever flooding MPRs are to be calculated, an implementation MUST
determine and record a set of flooding MPRs that is equivalent to one
calculated as described in this section.
The calculation of flooding MPRs need not use link metrics or, equivalently,
may use link metrics with a fixed value, here taken to be 1. However, links
with unknown metric (L_out_metric = UNKNOWN_METRIC) MUST NOT be used even
if link metrics are otherwise not used.
Routers MAY make individual decisions as to whether to use link metrics for
the calculation of flooding MPRs. A router MUST use the same approach to the
choice of whether to use link metrics for all links, i.e., in the cases
indicated by A or B, the same choice MUST be made in each case.
For each OLSRv2 interface (the "current interface"), define a Neighbor
Graph as defined in according to the
following:
Define a reachable Link Tuple to be a Link Tuple in the Link Set
for the current interface with L_status = SYMMETRIC and
L_out_metric != UNKNOWN_METRIC.
Define an allowed Link Tuple to be a reachable Link Tuple whose
corresponding Neighbor Tuple has N_will_flooding > WILL_NEVER.
Define an allowed 2-Hop Tuple to be a 2-Hop Tuple in the 2-Hop Set
for the current interface for which N2_out_metric != UNKNOWN_METRIC
and there is an allowed Link Tuple with
L_neighbor_iface_addr_list = N2_neighbor_iface_addr_list.
Define an element of N1 for each allowed Link Tuple. This then
defines the corresponding Link Tuple for each element of N1 and
the corresponding Neighbor Tuple for each element of N1, being the
Neighbor Tuple corresponding to that Link Tuple.
For each element x in N1, define W(x) := N_will_flooding of the
corresponding Neighbor Tuple.
For each element x in N1, define d1(x) as either:
L_out_metric of the corresponding Link Tuple; OR1.
Define an element of N2 for each network address that is the
N2_2hop_addr of one or more allowed 2-Hop Tuples. This then
defines the corresponding address for each element of N2.
For each element y in N2, if the corresponding address is in
the N_neighbor_addr_list of a Neighbor Tuple that corresponds
to one or more reachable Link Tuples, then define d1(y) as
either:
the minimum value of the L_out_metric of those Link Tuples; OR1.
Otherwise, d1(y) is not defined. In the latter case, where d1(y) := 1,
all such y in N2 may instead be removed from N2.
For each element x in N1, define N2(x) as the set of elements
y in N2 whose corresponding address is the N2_2hop_addr of an
allowed 2-Hop Tuple that has
N2_neighbor_iface_addr_list = L_neighbor_iface_addr_list
of the Link Tuple corresponding to x. For all such x and y,
define d2(x,y) as either:
N2_out_metric of that 2-Hop Tuple; OR1.
It is up to an implementation to decide how to label each element of N1
or N2. For example, an element of N1 may be labeled with one or more
addresses from the corresponding L_neighbor_iface_addr_list or with
a pointer or reference to the corresponding Link Tuple.
Using these Neighbor Graphs, flooding MPRs are selected and recorded by:
For each OLSRv2 interface, determine an MPR Set as specified in
.
A Neighbor Tuple represents a flooding MPR and has
N_flooding_mpr := true (otherwise, N_flooding_mpr := false) if and only
if that Neighbor Tuple corresponds to an element in an MPR Set created
for any interface as described above. That is, the overall set of
flooding MPRs is the union of the sets of flooding MPRs for all OLSRv2
interfaces.
A router MAY select its flooding MPRs for each OLSRv2 interface
independently, or it MAY coordinate its MPR selections across its
OLSRv2 interfaces, as long as the required condition is satisfied
for each OLSRv2 interface. One such coordinated approach is to
process the OLSRv2 interfaces sequentially and, for each OLSRv2
interface, start with flooding MPRs selected (and not removable)
if the neighbor has been already selected as an MPR for an
OLSRv2 interface that has already been processed. The algorithm
specified in can be used in this way.
Whenever routing MPRs are to be calculated, an implementation MUST
determine and record a set of routing MPRs that is equivalent to one
calculated as described in this section.
Define a single Neighbor Graph as defined in
according to the following:
Define a reachable Neighbor Tuple to be a Neighbor Tuple with
N_symmetric = true and N_in_metric != UNKNOWN_METRIC.
Define an allowed Neighbor Tuple to be a reachable Neighbor Tuple
with N_will_routing > WILL_NEVER.
Define an allowed 2-Hop Tuple to be a 2-Hop Tuple in the 2-Hop Set
for any OLSRv2 interface with N2_in_metric != UNKNOWN_METRIC and
for which there is an allowed Neighbor Tuple with N_neighbor_addr_list
containing N2_neighbor_iface_addr_list.
Define an element of N1 for each allowed Neighbor Tuple. This then
defines the corresponding Neighbor Tuple for each element of N1.
For each element x in N1, define W(x) := N_will_routing of the
corresponding Neighbor Tuple.
For each element x in N1, define d1(x) := N_in_metric of the
corresponding Neighbor Tuple.
Define an element of N2 for each network address that is the
N2_2hop_addr of one or more allowed 2-Hop Tuples. This then
defines the corresponding address for each element of N2.
For each element y in N2, if the corresponding address is in
the N_neighbor_addr_list of a reachable Neighbor Tuple, then
define d1(y) to be the N_in_metric of that Neighbor Tuple;
otherwise, d1(y) is not defined.
For each element x in N1, define N2(x) as the set of elements
y in N2 whose corresponding address is the N2_2hop_addr of an
allowed 2-Hop Tuple that has N2_neighbor_iface_addr_list
contained in N_neighbor_addr_list of the Neighbor Tuple
corresponding to x. For all such x and y, define
d2(x,y) := N2_out_metric of that 2-Hop Tuple.
It is up to an implementation to decide how to label each element of N1
or N2. For example, an element of N1 may be labeled with one or more
addresses from the corresponding N_neighbor_addr_list or with
a pointer or reference to the corresponding Neighbor Tuple.
Using these Neighbor Graphs, routing MPRs are selected and recorded according to the following:
Determine an MPR Set as specified in .
A Neighbor Tuple represents a routing MPR and has
N_routing_mpr := true (otherwise, N_routing_mpr := false) if and only
if that Neighbor Tuple corresponds to an element in the MPR Set created
as described above.
A router MUST recalculate each of its sets of MPRs whenever the currently
selected set of MPRs does not still satisfy the required conditions. It
MAY recalculate its MPRs if the current set of MPRs is still valid but
could be more efficient. Sufficient conditions to recalculate a router's
sets of MPRs are given in .
The Routing Set of a router is populated with Routing Tuples that
represent paths from that router to all destinations in the network.
These paths are calculated based on the Network Topology Graph,
which is constructed from information in the Information
Bases, obtained via HELLO and TC message exchange.
Changes to the Routing Set do not require any messages to be transmitted.
The state of the Routing Set SHOULD, however, be reflected in the IP routing
table by adding and removing entries from that routing table as appropriate.
Only appropriate Routing Tuples (in particular only those that represent
local links or paths to routable addresses) need be reflected in the IP
routing table.
The Network Topology Graph is formed from information from
the router's Local Interface Set, Link Sets for OLSRv2 interfaces,
Neighbor Set, Router Topology Set, Routable Address Topology Set,
and Attached Network Set. The Network Topology Graph MAY also
use information from the router's 2-Hop Sets for OLSRv2 interfaces.
The Network Topology Graph forms the router's topological view of
the network in the form of a directed graph. Each edge in that graph
has a metric value. The Network Topology Graph has a "backbone"
(within which minimum total metric routes will be constructed)
containing the following edges:
Edges X -> Y for all possible Y, and one X per Y, such that:
Y is the N_orig_addr of a Neighbor Tuple; AND
N_orig_addr is not unknown; AND
X is in the I_local_iface_addr_list of a Local Interface Tuple; AND
There is a Link Tuple with L_status = SYMMETRIC and L_out_metric != UNKNOWN_METRIC
such that this Neighbor Tuple and this Local Interface Tuple correspond to it.
A network address from L_neighbor_iface_addr_list will be denoted R in
this case.
It SHOULD be preferred, where possible, to select R = Y and to select X
from
the Local Interface Tuple corresponding to the Link Tuple from
which R was selected. The metric for such an edge is the
corresponding N_out_metric.
All edges W -> U such that:
W is the TR_from_orig_addr of a Router Topology Tuple; AND
U is the TR_to_orig_addr of the same Router Topology Tuple.
The metric of such an edge is the corresponding TR_metric.
The Network Topology Graph is further "decorated" with the following
edges. If a network address S, V, Z, or T equals a network address Y or W,
then the edge terminating in the network address S, V, Z, or T MUST NOT
be used in any path.
Edges X -> S for all possible S, and one X per S, such that:
S is in the N_neighbor_addr_list of a Neighbor Tuple; AND
X is in the I_local_iface_addr_list of a Local Interface Tuple; AND
There is a Link Tuple with L_status = SYMMETRIC and L_out_metric != UNKNOWN_METRIC
such that this Neighbor Tuple and this Local Interface Tuple correspond to it.
A network address from L_neighbor_iface_addr_list will be denoted
R in this case.
It SHOULD be preferred, where possible, to select R = S and to select
X from
the Local Interface Tuple corresponding to the Link Tuple from
which R was selected. The metric for such an edge is the
corresponding N_out_metric.
All edges W -> V such that:
W is the TA_from_orig_addr of a Routable Address Topology Tuple; AND
V is the TA_dest_addr of the same Routable Address Topology Tuple.
The metric for such an edge is the corresponding TA_metric.
All edges W -> T such that:
W is the AN_orig_addr of an Attached Network Tuple; AND
T is the AN_net_addr of the same Attached Network Tuple.
The metric for such an edge is the corresponding AN_metric.
(OPTIONAL) All edges Y -> Z such that:
Z is a routable address and is the N2_2hop_addr of a 2-Hop Tuple
with N2_out_metric != UNKNOWN_METRIC; AND
Y is the N_orig_addr of the corresponding Neighbor Tuple; AND
This Neighbor Tuple has N_will_routing not equal to WILL_NEVER.
A path terminating with such an edge MUST NOT be used in preference
to any other path. The metric for such an edge is the corresponding
N2_out_metric.
Any part of the Topology Graph that is not connected to a local network address
X is not used. Only one selection X SHOULD be made from each I_local_iface_addr_list,
and only one selection R SHOULD be made from any L_neighbor_iface_addr_list.
All edges have a hop count of 1, except edges W -> T that have a hop count of the
corresponding value of AN_dist.
The Routing Set MUST contain the shortest paths for all destinations
from all local OLSRv2 interfaces using the Network Topology Graph.
This calculation MAY use any algorithm, including any means of choosing
between paths of equal total metric. (In the case of two paths of equal
total metric but differing hop counts, the path with the lower hop
count SHOULD be used.)
Using the notation of , initially "backbone" paths
using only edges X -> Y and W -> U need be constructed (using a minimum distance
algorithm). Then paths using only a final edge of the other types may be added.
These MUST NOT replace backbone paths with the same destination (and paths
terminating in an edge Y -> Z SHOULD NOT replace paths with any other form of
terminating edge).
Each path will correspond to a Routing Tuple. These will be of two types.
The first type will represent single edge paths, of type X -> S or X -> Y,
by:
R_local_iface_addr := X;R_next_iface_addr := R;R_dest_addr := S or Y;R_dist := 1;R_metric := edge metric,
where R is as defined in for these types
of edge.
The second type will represent a multiple edge path, which will always have first edge
of type X -> Y, and will have final edge of type W -> U, W -> V, W -> T, or Y -> Z.
The Routing Tuple will be:
R_local_iface_addr := X; R_next_iface_addr := Y;R_dest_addr := U, V, T or Z;R_dist := the total hop count of all edges in the path;R_metric := the total metric of all edges in the path.
Finally, Routing Tuples of the second type whose R_dest_addr is not routable
MAY be discarded.
An example algorithm for calculating the Routing Set of a router is given
in .
This protocol uses all parameters defined in
and additional parameters defined in this specification. All but
one (RX_HOLD_TIME) of these additional parameters are router parameters as
defined in . The proposed values of the additional
parameters defined in the following sections are appropriate to the case
where all parameters (including those defined in )
have a single value. Proposed values for parameters defined in
are given in that specification.
The following proposed values are based on experience with
deployments (such as documented in ) and are considered
typical. They can be changed to accommodate different deployment requirements
-- for example, a network with capacity-limited network interfaces would be expected
to use greater values for message intervals, whereas a highly mobile network would
be expected to use lower values for message intervals. When determining these values,
the constraints specified in MUST be respected.
Note that routers in a MANET need not all use the same set of parameters, and those parameters that are indicated as interface parameters need not be the same on all OLSRv2 interfaces of a single router.
O_HOLD_TIME := 30 secondsTC_INTERVAL := 5 secondsTC_MIN_INTERVAL := TC_INTERVAL/4T_HOLD_TIME := 3 x TC_INTERVALA_HOLD_TIME := T_HOLD_TIMERX_HOLD_TIME := 30 secondsP_HOLD_TIME := 30 secondsF_HOLD_TIME := 30 secondsTP_MAXJITTER := HP_MAXJITTERTT_MAXJITTER := HT_MAXJITTERF_MAXJITTER := TT_MAXJITTERTC_HOP_LIMIT := 255WILL_FLOODING := WILL_DEFAULTWILL_ROUTING := WILL_DEFAULT
Sequence numbers are used in this specification for the purpose of
discarding "old" information, i.e., messages received out of order.
However, with a limited number of bits for representing sequence numbers,
wraparound (in which the sequence number is incremented from the maximum
possible value to zero) will occur. To prevent this from interfering
with the operation of this protocol, the following MUST be observed when
determining the ordering of sequence numbers.
The term MAXVALUE designates in the following one more than
the largest possible value for a sequence number. For a 16-bit sequence
number (like those defined in this specification),
MAXVALUE is 65536.
The sequence number S1 is said to be "greater than" the sequence
number S2 if:
S1 > S2 AND S1 - S2 < MAXVALUE/2, OR S2 > S1 AND S2 - S1 > MAXVALUE/2
When sequence numbers S1 and S2 differ by MAXVALUE/2, their ordering
cannot be determined. In this case, which should not occur, either
ordering may be assumed.
Thus, when comparing two messages, it is possible -- even in the
presence of wraparound -- to determine which message contains the
most recent information.
An extension to this protocol will need to interact with this specification
and possibly also with . This protocol is designed to
permit such interactions, in particular:
Through accessing, and possibly extending, the information in the
Information Bases. All updates to the elements specified in this
specification are subject to the normative constraints specified in
and . Note that
the processing specified in this document ensures that these
constraints are satisfied.
Through accessing an outgoing message prior to it being
transmitted over any OLSRv2 interface and adding information
to it as specified in . This MAY
include Message TLVs and/or network addresses with associated
Address Block TLVs. (Network addresses without new associated
TLVs SHOULD NOT be added to messages.) This may, for example,
be to allow a security protocol, as suggested in
, to add a TLV containing a
cryptographic signature to the message.
Through accessing an incoming message and potentially discarding
it prior to processing by this protocol. This may, for example,
allow a security protocol, as suggested in ,
to perform verification of message signatures and prevent
processing and/or forwarding of unverifiable messages by this
protocol.
Through accessing an incoming message after it has been completely
processed by this protocol. In particular, this may allow a protocol
that has added information, by way of inclusion of appropriate TLVs
or of network addresses associated with new TLVs, access to such information
after appropriate updates have been recorded in the Information Bases
in this protocol.
Through requesting that a message be generated at a specific time.
In that case, message generation MUST still respect the constraints
in and .
As a proactive routing protocol, OLSRv2 is a potential target for various attacks.
This section presents the envisioned security architecture for OLSRv2 and gives guidelines
on how to provide integrity, confidentiality, and integration into external routing domains.
Separately specified mandatory security mechanisms are summarized, and some observations on
key management are given.
OLSRv2 integrates into the architecture specified in Appendix A of ,
in , and in Section 16 of ,
the latter by using and extending its messages and Information Bases.
As part of this architecture, OLSRv2 and NHDP recognize that there may be external
reasons for rejecting messages that would be considered "badly formed" or "insecure",
e.g., if an Integrity Check Value (ICV) included in a message by an external mechanism cannot be
verified. This architecture allows options as to whether and how to implement security
features, reflecting the situation that MANET routing protocol deployment domains have
varying security requirements, ranging from "practically unbreakable" to "virtually none".
This approach allows MANET routing protocol specifications to remain generic, with
extensions to them and/or extensions to the multiplexing and demultiplexing process
described in Appendix A of , providing security mechanisms
appropriate to a given deployment domain.
The following sections provide guidelines on how to provide integrity, confidentiality, and
integration with external routing domains in such extensions.
Each router injects topological information into the network by transmitting HELLO messages
and, for some routers, also TC messages. If some routers for some reason (malice or malfunction)
inject invalid control traffic, network integrity may be compromised. Therefore, message,
or packet, authentication is strongly advised.
Different such situations may occur, for example:
A router generates TC messages, advertising links to non-neighbor routers;
A router generates TC messages, pretending to be another router;
A router generates HELLO messages, advertising non-neighbor routers;
A router generates HELLO messages, pretending to be another router;
A router forwards altered control messages;
A router does not forward control messages;
A router does not select multipoint relays correctly;
A router forwards broadcast control messages unaltered but does not forward
unicast data traffic;
A router "replays" previously recorded control traffic from another router.
Authentication of the originator router for control messages (for
situations 2, 4, and 5) and of the individual links announced in the
control messages (for situations 1 and 3) may be used as a
countermeasure. However, to prevent routers from repeating old (and
correctly authenticated) information (situation 9), additional
information is required (e.g., a timestamp or sequence number), allowing a router to positively identify such replayed messages.
In general, ICVs (e.g., digital signatures) and other required security information
can be transmitted within the HELLO and TC messages or within a packet
header using the TLV mechanism. Either option permits different levels
of protection to coexist in the same network, if desired.
An important consideration is that all control messages (HELLO messages
and TC messages) are transmitted to all routers in the 1-hop neighborhood
and some control messages (TC messages) are flooded to all routers in the network.
This is done in a packet that is transmitted to all routers in the 1-hop neighborhood,
the current set of which may not be known. Thus, a control message or
packet used by this protocol is always contained in a transmission destined for
multiple destinations, and it is important that the authentication mechanism employed
permits any receiving router to validate the authenticity of a message or
packet.
specifies a common exchange format for cryptographic
information in the form of Packet TLVs, Message TLVs, and Address Block TLVs,
as specified in . These may be used (and shared) among
MANET routing protocol security extensions. In particular,
specifies the format of TLVs for containing Integrity Check Values (ICVs), i.e.,
signatures, for providing integrity, as well as TLVs for containing temporal information for
preventing replay attacks. specifies registries for using different
ciphers and formats of temporal information. When using ICV TLVs in an OLSRv2 deployment,
failure to verify an included ICV mandates rejection of an incoming message or packet as "invalid", according
to Section 12.1 of and according to
of this specification when using the multiplexing and demultiplexing process described in
Appendix A of .
specifies how to
insert ICVs into generated messages, how to verify incoming messages, and to reject
"insecure" messages (i.e., messages without an ICV or with an ICV that cannot be
verified). Different MANET deployments may, as a
result of the purpose for which they are used and the possibility and nature of
their configuration, require different ICV algorithms and timestamps or multiple keys,
and thus, a security extension may use any of the different options provided in
.
OLSRv2 periodically MPR floods topological information to all routers in the network.
Hence, if used in an unprotected network, in particular, an unprotected wireless network,
the network topology is revealed to anyone who successfully listens to the control
messages. This information may serve an attacker to acquire details about the topology
and therefore to initiate more effective attacks against routers in the routing domain,
e.g., by spoofing addresses of routers in the network and attracting traffic for these
addresses. Note that this is independent of the data traffic and purely protects the
control traffic, i.e., information about the network topology.
In situations where the confidentiality of the network topology is of importance,
regular cryptographic techniques, such as use of OLSRv2 multicast control packets
encrypted using IPsec (e.g., with a shared secret key), can be applied to ensure that
control traffic can be read and interpreted by only those authorized to do so.
Alternatively, a security extension may specify a mechanism to provide confidentiality
for control messages and/or packets. However, unless the information about the network
topology itself is confidential, integrity of control messages (as specified in
) is sufficient to admit only trusted routers (i.e., routers
with valid credentials) to the network.
This protocol provides a basic mechanism for injecting external routing information
into this protocol's routing domain. Routing information can also be extracted from this
protocol's Information Bases, in particular the Routing Set, and injected into an
external routing domain, if the routing protocol governing that routing domain permits this.
When operating routers connecting a routing domain using this protocol to an external routing
domain, care MUST be taken not to allow potentially insecure and untrustworthy information
to be injected from this routing domain to an external routing domain. Care MUST also be
taken to validate the correctness of information prior to it being injected, so as to avoid
polluting routing tables with invalid information.
A recommended way of extending connectivity from an external routing domain to this
routing domain, which is routed using this protocol, is to assign an IP prefix (under the
authority of the routers/gateways connecting this routing domain with the external
routing domain) exclusively to this routing domain and to configure the gateways
to advertise routes for that IP prefix into the external routing domain.
A conformant implementation of OLSRv2 MUST, at minimum, implement the security mechanisms
specified in , providing integrity and replay protection
of OLSRv2 control messages, including of HELLO messages specified by
and used by OLSRv2, by inclusion of a timestamp TLV and an Integrity Check Value (ICV) TLV.
This ICV TLV uses a SHA-256-based HMAC and one or more manually managed shared secret keys.
The timestamp TLV is based on Portable Operating System Interface (POSIX) time, assuming router time synchronization.
The baseline use case, for which this security mechanism provides adequate integrity
protection without rekeying, is for short-lived (for example, up to a couple of months)
OLSRv2 deployments.
Any deployment of OLSRv2 SHOULD use the security mechanism specified in
but MAY use another mechanism if more appropriate
in an OLSRv2 deployment. For example, for longer-term OLSRv2 deployments, alternative
security mechanisms (e.g., rekeying) SHOULD be considered.
This specification, as well as , does not mandate
automated key management (AKM) as part of the security architecture for OLSRv2.
While some use cases for OLSRv2 may require AKM, the baseline assumption is that
many use cases do not, for the reasons detailed below.
Bootstrapping a key is hard in a radio network, where it is, in general, not
possible to determine from where a received signal was transmitted or if two
transmissions come from the same or from different sources.
The widespread use of radio networks and mobile phone networks works under the
assumptions that (i) secret information is embedded in mobile phones at manufacture,
and (ii) a centralized database of this is accessible during the network lifetime.
As a primary use case of a MANET is to provide connectivity without centralized
entities and with minimal management, a solution such as described in the previous
paragraph is not feasible. In many instances, a cryptographic authority may not be
present in the MANET at all, since such a cryptographic authority would be
too vulnerable. Due to the potentially dynamic topology of a MANET, a
cryptographic authority may also become unreachable (to some or all of the MANET
routers) without prior warning.
provides guidelines for cryptographic key management.
Specifically, Section 2.1 sets forth requirements for when AKM is required,
and Section 2.2 sets forth conditions under which manual key management is
acceptable.
Section 2.1 of stipulates that "Automated key management
MUST be used if any of [a set of given] conditions hold". These conditions are
listed below, and arguments for each are provided in regard to their applicability for the baseline use case of OLSRv2.
A party will have to manage n^2 static keys, where n may become large.
The baseline use case of OLSRv2 uses only one or a small set of manually managed shared secrets in the whole MANET.
Any stream cipher (such as RC4 , AES-CTR , or AES-CCM ) is used.
A stream cipher is not envisioned for use to generate ICVs for OLSRv2 control messages.
An initialization vector (IV) might be reused, especially an
implicit IV. Note that random or pseudo-random explicit IVs are not a problem unless the probability of repetition is high.
An IV is not envisioned for use to generate ICVs for OLSRv2 control messages.
Large amounts of data might need to be encrypted in a short time, causing frequent change of the short-term session key.
Integrity Check Values (ICVs) are required only for OLSRv2 control messages, which are low-volume messages.
Long-term session keys are used by more than two
parties. Multicast is a necessary exception, but multicast key management
standards are emerging in order to avoid this in the future. Sharing long-term
session keys should generally be discouraged.
OLSRv2 control messages are all sent using link-local multicast.
The likely operational environment is one where personnel
(or device) turnover is frequent, causing frequent change of the short-term
session key.
This is not an intended deployment of OLSRv2. For longer-term OLSRv2 deployments, alternative
security mechanisms (e.g., including rekeying) SHOULD be considered.
Section 2.2 of stipulates that "Manual key management may be a
reasonable approach in any of [a given set of] situations". These situations are listed
below, and arguments for each are provided in regard to their applicability for the baseline
use case of OLSRv2.
The environment has very limited available bandwidth or very high round-trip times. Public key systems tend to require long messages and lots of computation; symmetric key alternatives, such as Kerberos, often require several round trips and interaction with third parties.
As previously noted, there may not be the required infrastructure (cryptographic authority)
present (or, if present, may not be reachable) in the MANET. Bandwidth in a MANET is commonly
limited, both by being a radio environment and by the need for any signaling to consume a
minimal proportion thereof, and round trip times may also be significant.
The information being protected has low value.
This depends on the OLSRv2 use case, but the information being protected is OLSRv2
control traffic, which is of at least moderate value; thus, this case does not apply.
The total volume of traffic over the entire lifetime of the long-term session key will be very low.
Integrity Check Values (ICVs) are required only for OLSRv2 control messages, which are low-volume messages.
The scale of each deployment is very limited.
A typical use case for OLSRv2 may involve only tens of devices --
with even the largest use cases for OLSRv2 being small by Internet
standards.
This specification defines one Message Type, which has been allocated
from the "Message Types" registry of ,
two Message TLV Types, which have been allocated from the "Message TLV Types"
registry of , and four Address Block TLV Types,
which have been allocated from the "Address Block TLV Types" registry of
.
For the registries where an Expert Review is required, the designated
expert SHOULD take the same general recommendations into consideration
as are specified by .
This specification defines one Message Type, allocated from the
0-223 range of the "Message Types" namespace defined in
, as specified in .
TypeDescription1TC : Topology Control (MANET-wide signaling)
IANA has created a registry for Message-Type-specific
Message TLVs for TC messages, in accordance with Section 6.2.1 of
and with initial assignments and allocation
policies as specified in .
TypeDescriptionAllocation Policy128-223UnassignedExpert Review
IANA has created a registry for Message-Type-specific
Address Block TLVs for TC messages, in accordance with Section 6.2.1 of
and with initial assignments and allocation
policies as specified in .
TypeDescriptionAllocation Policy128-223UnassignedExpert Review
This specification defines two Message TLV Types, which have been allocated
from the "Message TLV Types" namespace defined in .
IANA has made allocations in the 0-127 range for these types.
Two new Type Extension registries have been created with assignments as
specified in and
.
Specifications of these TLVs are in . Each of
these TLVs MUST NOT be included more than once in a Message TLV Block.
NameTypeType ExtensionDescriptionAllocation PolicyMPR_WILLING70Bits 0-3 specify the originating router's willingness to act as a flooding MPR;
bits 4-7 specify the originating router's willingness to act as a routing MPR.MPR_WILLING71-255Unassigned.Expert ReviewNameTypeType ExtensionDescriptionAllocation PolicyCONT_SEQ_NUM80 COMPLETE: Specifies a content sequence number for this complete message.CONT_SEQ_NUM81INCOMPLETE: Specifies a content sequence number for this incomplete message.CONT_SEQ_NUM82-255Unassigned.Expert Review
Type extensions indicated as Expert Review SHOULD be allocated as
described in , based on Expert Review as
defined in .
This specification defines four Address Block TLV Types, which have been allocated
from the "Address Block TLV Types" namespace defined in .
IANA has made allocations in the 8-127 range for these types.
Four new Type Extension registries have been created with assignments as
specified in Tables 13, 14, 15, and 16. Specifications of these TLVs are in .
The registration procedure for the "LINK_METRIC Address Block TLV Type
Extensions" registry is Expert Review.NameTypeType ExtensionDescriptionLINK_METRIC70Link metric meaning assigned by administrative action.LINK_METRIC71-223Unassigned.LINK_METRIC7224-255Reserved for Experimental
Use
All LINK_METRIC TLVs, whatever their type extension, MUST use their value field to
encode the kind and value (in the interval MINIMUM_METRIC to MAXIMUM_METRIC,
inclusive) of a link metric as specified in Sections
and
. An assignment of a LINK_METRIC TLV type extension MUST specify
the physical meaning of the link metric and the mapping of that physical meaning to the representable values
in the indicated interval.
NameTypeType ExtensionDescriptionAllocation PolicyMPR80Specifies that a given network address is of a router selected as a flooding MPR
(FLOODING = 1), that a given network address is of a router selected as a routing MPR
(ROUTING = 2), or both (FLOOD_ROUTE = 3).MPR81-255Unassigned.Expert ReviewNameTypeType ExtensionDescriptionAllocation PolicyNBR_ADDR_TYPE90Specifies that a given network address is of a neighbor reached via the originating router,
if it is an originator address (ORIGINATOR = 1), is a routable address (ROUTABLE = 2),
or if it is both (ROUTABLE_ORIG = 3).NBR_ADDR_TYPE91-255Unassigned.Expert ReviewNameTypeType extensionDescriptionAllocation PolicyGATEWAY100Specifies that a given network address is reached via a gateway on the
originating router, with value equal to the number of hops.GATEWAY101-255Expert Review
Type extensions indicated as Expert Review SHOULD be allocated as
described in , based on Expert Review as
defined in .
Note: This section does not require any IANA action, as the required information
is included in the descriptions of the MPR and NBR_ADDR_TYPE Address Block TLVs
allocated in . This information is recorded here
for clarity and for use elsewhere in this specification.
The Values that the MPR Address Block TLV can use are as follows:
FLOODING := 1;ROUTING := 2;FLOOD_ROUTE := 3.
The Values that the NBR_ADDR_TYPE Address Block TLV can use are follows:
ORIGINATOR := 1;ROUTABLE := 2;ROUTABLE_ORIG := 3.
This specification is the result of the joint efforts of the following
contributors, listed alphabetically.
Cedric Adjih, INRIA, France, <Cedric.Adjih@inria.fr>Emmanuel Baccelli, INRIA , France,
<Emmanuel.Baccelli@inria.fr>Thomas Heide Clausen, LIX, France, <T.Clausen@computer.org>Justin Dean, NRL, USA, <jdean@itd.nrl.navy.mil>Christopher Dearlove, BAE Systems, UK,
<chris.dearlove@baesystems.com>Ulrich Herberg, Fujitsu Laboratories of America, USA,
<ulrich@herberg.name>Satoh Hiroki, Hitachi SDL, Japan,
<hiroki.satoh.yj@hitachi.com>Philippe Jacquet, Alcatel Lucent Bell Labs, France,
<philippe.jacquet@alcatel-lucent.fr>Monden Kazuya, Hitachi SDL, Japan,
<kazuya.monden.vw@hitachi.com>Kenichi Mase, Niigata University, Japan,
<mase@ie.niigata-u.ac.jp>Ryuji Wakikawa, Toyota, Japan, <ryuji@sfc.wide.ad.jp>
The authors would like to acknowledge the team behind OLSRv1,
as listed in RFC 3626, including Anis Laouiti (INT), Pascale Minet (INRIA),
Paul Muhlethaler (INRIA), Amir Qayyum (M.A. Jinnah University), and
Laurent Viennot (INRIA) for their contributions.
The authors would like to gratefully acknowledge the following people for
intense technical discussions, early reviews, and comments on the specification
and its components (listed alphabetically): Khaldoun Al Agha (LRI),
Teco Boot (Infinity Networks), Ross Callon (Juniper), Song-Yean Cho (Samsung), Alan Cullen (BAE Systems),
Louise Lamont (CRC), Li Li (CRC), Joseph Macker (NRL), Richard Ogier (SRI),
Charles E. Perkins (Futurewei), Henning Rogge (Frauenhofer FKIE), and the entire
IETF MANET Working Group.
Finally, the authors would like to express their gratitude to the Area Directors for providing valuable review comments during the IESG evaluation, in particular (listed alphabetically) Benoit Claise, Adrian Farrel, Stephen Farrell, Barry Leiba, Pete Resnick, and Martin Stiemerling.
Integrity Check Value and Timestamp TLV Definitions for Mobile Ad Hoc Networks (MANETs)
Integrity Protection for the Neighborhood Discovery Protocol (NHDP) and
Optimized Link State Routing Protocol Version 2 (OLSRv2)
Fujitsu Laboratories of AmericaBAE Systems ATCLIX, Ecole PolytechniqueRadio Equipment and Systems (RES);
HIgh PErformance Radio Local Area Network (HIPERLAN) Type 1;
Functional SpecificationETSIIncreasing Reliability in Cable-Free Radio LANs: Low Level Forwarding in HIPERLANProject Hipercom, INRIA Rocquencourt, FranceProject Hipercom, INRIA Rocquencourt, FranceProject Hipercom, INRIA Rocquencourt, FranceProject Hipercom, INRIA Rocquencourt, FranceMultipoint Relaying: An Efficient Technique for Flooding in Mobile Wireless NetworksProject Hipercom, INRIA Rocquencourt, FranceProject Hipercom, INRIA Rocquencourt, FranceProject Hipercom, INRIA Rocquencourt, FranceFisheye State Routing in Mobile Ad Hoc NetworksComputer Science Department, University of California, Los Angeles, USAComputer Science Department, University of California, Los Angeles, USABell Laboratories, Lucent Technologies, USAMaking Link-State Routing Scale for Ad Hoc NetworksBBN Technologies, MA, USABBN Technologies, MA, USABBN Technologies, MA, USAScalability Modelling of Ad Hoc Routing Protocols - A Comparison of OLSR and DSRGuidelines for Cryptographic Key ManagementApplied Cryptography: Protocols, Algorithms, and Source Code in
CRecommendation for Block Cipher Modes of Operation: Methods and
TechniquesNational Institute of Standards and
TechnologyRecommendation for Block Cipher Modes of Operation: The CCM Mode
for Authentication and ConfidentialityNational Institute of Standards and
Technology
Updates to the Local Information Base, the Neighborhood Information Base, or the Topology Information Base MUST ensure that all constraints specified in this appendix are maintained, as well as those specified in . This is the case for the processing, specified in this document. Any protocol extension or outside process, which updates the Neighborhood Information Base or the Topology Information Base, MUST also ensure that these constraints are maintained.
In each Originator Tuple:
O_orig_addr MUST NOT equal any other O_orig_addr.
O_orig_addr MUST NOT equal this router's originator address.
In each Local Attached Network Tuple:
AL_net_addr MUST NOT equal any other AL_net_addr.
AL_net_addr MUST NOT equal or be a sub-range of any network address in the
I_local_iface_addr_list of any Local Interface Tuple.
AL_net_addr MUST NOT equal this router's originator address or
equal the O_orig_addr in any Originator Tuple.
AL_dist MUST NOT be less than zero.
In each Link Tuple:
L_neighbor_iface_addr_list MUST NOT contain any network address that
AL_net_addr of any Local Attached Network Tuple equals or is a sub-range of.
If L_in_metric != UNKNOWN_METRIC, then L_in_metric MUST be representable in
the defined compressed form.
If L_out_metric != UNKNOWN_METRIC, then L_out_metric MUST be representable in
the defined compressed form.
If L_mpr_selector = true, then L_status = SYMMETRIC.
In each Neighbor Tuple:
N_orig_addr MUST NOT be changed to unknown.
N_orig_addr MUST NOT equal this router's originator address or
equal O_orig_addr in any Originator Tuple.
N_orig_addr MUST NOT equal the AL_net_addr in any Local Attached
Network Tuple.
If N_orig_addr != unknown, then N_orig_addr MUST NOT equal the
N_orig_addr in
any other Neighbor Tuple.
N_neighbor_addr_list MUST NOT contain any network address that
includes
this router's originator address, the O_orig_addr in any Originator
Tuple,
or equal or have as a sub-range the AL_net_addr in any Local Attached
Network Tuple.
If N_orig_addr = unknown, then N_will_flooding = WILL_NEVER,
N_will_routing = WILL_NEVER, N_flooding_mpr = false,
N_routing_mpr = false, N_mpr_selector = false, and
N_advertised = false.
N_in_metric MUST equal the minimum value of the L_in_metric values of
all
corresponding Link Tuples with L_status = SYMMETRIC and L_in_metric !=
UNKNOWN_METRIC,
if any; otherwise, N_in_metric = UNKNOWN_METRIC.
N_out_metric MUST equal the minimum value of the L_out_metric values of
all
corresponding Link Tuples with L_status = SYMMETRIC and L_out_metric !=
UNKNOWN_METRIC,
if any; otherwise, N_out_metric = UNKNOWN_METRIC.
N_will_flooding and N_will_routing MUST be in the range from WILL_NEVER
to WILL_ALWAYS, inclusive.
If N_flooding_mpr = true, then N_symmetric MUST be true, N_out_metric
MUST NOT equal UNKNOWN_METRIC, and N_will_flooding MUST NOT equal
WILL_NEVER.
If N_routing_mpr = true, then N_symmetric MUST be true, N_in_metric
MUST NOT equal UNKNOWN_METRIC, and N_will_routing MUST NOT equal
WILL_NEVER.
If N_symmetric = true and N_flooding_mpr = false, then N_will_flooding
MUST NOT equal WILL_ALWAYS.
If N_symmetric = true and N_routing_mpr = false, then N_will_routing
MUST NOT equal WILL_ALWAYS.
If N_mpr_selector = true, then N_advertised MUST be true.
If N_advertised = true, then N_symmetric MUST be true and
N_out_metric MUST NOT equal UNKNOWN_METRIC.
In each Lost Neighbor Tuple:
NL_neighbor_addr MUST NOT include this router's originator address,
the O_orig_addr in any Originator Tuple, or equal or have as a sub-range the
AL_net_addr in any Local Attached Network Tuple.
In each 2-Hop Tuple:
N2_2hop_addr MUST NOT equal this router's originator address,
equal the O_orig_addr in any Originator Tuple, or equal or have as a
sub-range the AL_net_addr in any Local Attached Network Tuple.
If N2_in_metric != UNKNOWN_METRIC, then N2_in_metric MUST be representable in
the defined compressed form.
If N2_out_metric != UNKNOWN_METRIC, then N2_out_metric MUST be representable in
the defined compressed form.
In each Advertising Remote Router Tuple:
AR_orig_addr MUST NOT be in any network address in the
I_local_iface_addr_list in any Local Interface Tuple or
be in the IR_local_iface_addr in any Removed Interface
Address Tuple.
AR_orig_addr MUST NOT equal this router's originator address
or equal the O_orig_addr in any Originator Tuple.
AR_orig_addr MUST NOT be in the AL_net_addr in any
Local Attached Network Tuple.
AR_orig_addr MUST NOT equal the AR_orig_addr in any other
Advertising Remote Router Tuple.
In each Router Topology Tuple:
There MUST be an Advertising Remote Router Tuple with
AR_orig_addr = TR_from_orig_addr.
TR_to_orig_addr MUST NOT be in any network address in the
I_local_iface_addr_list in any Local Interface Tuple or be in the
IR_local_iface_addr in any Removed Interface Address Tuple.
TR_to_orig_addr MUST NOT equal this router's originator address
or equal the O_orig_addr in any Originator Tuple.
TR_to_orig_addr MUST NOT be in the AL_net_addr in any
Local Attached Network Tuple.
The ordered pair (TR_from_orig_addr, TR_to_orig_addr) MUST NOT
equal the corresponding pair for any other Router Topology Tuple.
TR_seq_number MUST NOT be greater than AR_seq_number in the Advertising
Remote Router Tuple with AR_orig_addr = TR_from_orig_addr.
TR_metric MUST be representable in the defined compressed form.
In each Routable Address Topology Tuple:
There MUST be an Advertising Remote Router Tuple with
AR_orig_addr = TA_from_orig_addr.
TA_dest_addr MUST be routable.
TA_dest_addr MUST NOT overlap any network address in the I_local_iface_addr_list
in any Local Interface Tuple or overlap the IR_local_iface_addr in any
Removed Interface Address Tuple.
TA_dest_addr MUST NOT include this router's originator address or
include the O_orig_addr in any Originator Tuple.
TA_dest_addr MUST NOT equal or have as a sub-range the AL_net_addr in any
Local Attached Network Tuple.
The ordered pair (TA_from_orig_addr, TA_dest_addr) MUST NOT equal
the corresponding pair for any other Attached Network Tuple.
TA_seq_number MUST NOT be greater than AR_seq_number in the Advertising
Remote Router Tuple with AR_orig_addr = TA_from_orig_addr.
TA_metric MUST be representable in the defined compressed form.
In each Attached Network Tuple:
There MUST be an Advertising Remote Router Tuple with
AR_orig_addr = AN_orig_addr.
AN_net_addr MUST NOT equal or be a sub-range of any network
address in the I_local_iface_addr_list in any Local Interface
Tuple or equal or be a sub-range of the IR_local_iface_addr in any
Removed Interface Address Tuple.
AN_net_addr MUST NOT equal this router's originator address
or equal the O_orig_addr in any Originator Tuple.
The ordered pair (AN_orig_addr, AN_net_addr) MUST NOT equal
the corresponding pair for any other Attached Network Tuple.
AN_seq_number MUST NOT be greater than AR_seq_number in the
Advertising Remote Router Tuple with AR_orig_addr = AN_orig_addr.
AN_dist MUST NOT be less than zero.
AN_metric MUST be representable in the defined compressed form.
The following specifies an algorithm that MAY be used to select
an MPR Set given a Neighbor Graph, as defined in
and .
This algorithm selects an MPR Set M that is a subset of the set N1
that is part of the Neighbor Graph. This algorithm assumes that a
subset I of N1 is pre-selected as MPRs, i.e., that M will contain I.
The following additional notation, in addition to that in
, will be used by this algorithm:
A subset of N2, consisting of those elements y in N2 such that
either d1(y) is not defined, or there is at least one x in N1
such that d(x,y) is defined and d(x,y) < d1(y).
For an element x in N1, the number of elements y in N for
which d(x,y) is defined and has minimal value among the
d(z,y) for all z in N1.
For an element x in N1, the number of elements y in N for
which d(x,y) is defined has minimal value among the d(z,y)
for all z in N1 and no such minimal values have z in M.
(Note that, denoting the empty set by 0, D(x) = R(x,0).)
To create the MPR Set M, starting with M := I:
Add all elements x in N1 that have W(x) = WILL_ALWAYS to M.
For each element y in N for which there is only one element x in N1
such that d2(x,y) is defined, add that element x to M.
While there exists any element x in N1 with R(x,M) > 0:
Select an element x in N1 with R(x,M) > 0 in the following order of
priority, and then add to M:
greatest W(x), THEN
greatest R(x,M), THEN
greatest D(x), THEN
any choice, which MAY be based on other criteria (for example, a
router MAY choose to prefer a neighbor as an MPR if that neighbor
has already selected the router as an MPR of the same type, MAY
prefer a neighbor based on information freshness, or MAY prefer
a neighbor based on length of time previously selected as an MPR)
or MAY be random.
OPTIONAL: consider each element x in M, but not in I, in turn
and if x can be removed from M while still leaving it satisfying
the definition of an MPR Set, then remove that element x from M.
Elements MAY be considered in any order, e.g., in order of
increasing W(x).
The following procedure is given as an example for calculating
the Routing Set using a variation of Dijkstra's algorithm. First,
all Routing Tuples are removed, and then, using the selections
and definitions in , the procedures
in the following sections (each considered a "stage" of the processing)
are applied in turn.
The following selections and definitions are made:
For each Local Interface Tuple, select a network address from its
I_local_iface_addr_list. This is defined as the selected address
for this Local Interface Tuple.
For each Link Tuple, the selected address of its corresponding
Local Interface Tuple is defined as the selected local address
for this Link Tuple.
For each Neighbor Tuple with N_symmetric = true and N_out_metric != UNKNOWN_METRIC,
select a Link Tuple with L_status = SYMMETRIC for which this is the corresponding
Neighbor Tuple and has L_out_metric = N_out_metric. This is
defined as the selected Link Tuple for this Neighbor Tuple.
For each network address (N_orig_addr or in N_neighbor_addr_list,
the "neighbor address") from a Neighbor Tuple with N_symmetric = true
and N_out_metric != UNKNOWN_METRIC, select a Link Tuple (the "selected
Link Tuple") from those for which this is the corresponding Neighbor
Tuple, have L_status = SYMMETRIC, and have L_out_metric = N_out_metric, by:
If there is such a Link Tuple whose L_neighbor_iface_addr_list
contains the neighbor address, select that Link Tuple.
Otherwise, select the selected Link Tuple for this Neighbor Tuple.
Then for this neighbor address:
The selected local address is defined as the selected local address
for the selected Link Tuple.
The selected link address is defined as an address from the
L_neighbor_iface_addr_list of the selected Link Tuple, if possible
equal to this neighbor address.
Routing Tuple preference is decided by preference for minimum
R_metric, then for minimum R_dist, and then for preference for
corresponding Neighbor Tuples in this order:
For greater N_will_routing.
For N_mpr_selector = true over N_mpr_selector = false.
Note that preferred Routing Tuples SHOULD be used. Routing Tuples with
minimum R_metric MUST be used; this is specified outside the definition
of preference. An implementation MAY modify this definition of preference
(including for minimum R_dist) without otherwise affecting this algorithm.
The following procedure is executed once.
For each Neighbor Tuple with N_symmetric = true and N_out_metric != UNKNOWN_METRIC,
add a Routing Tuple with:
R_dest_addr := N_orig_addr;R_next_iface_addr := selected link address for N_orig_addr;R_local_iface_addr := selected local address for N_orig_addr;R_metric := N_out_metric;R_dist := 1.
The following procedure is executed once.
Add a label that may be "used" or "unused" to each Routing Tuple,
with all initial values equal to unused. (Note that this label is
only required during this algorithm.)
If there are no unused Routing Tuples, then this stage is complete;
otherwise, repeat the following until that is the case.
Find the unused Routing Tuple with minimum R_metric (if more than one,
pick any) and denote it the "current Routing Tuple".
Mark the current Routing Tuple as used.
For each Router Topology Tuple, with
TR_from_orig_addr = R_dest_addr of the current Routing Tuple:
Define:
new_metric := R_metric of the current Routing Tuple + TR_metric;new_dist := R_dist of the current Routing Tuple + 1.
If there is no Routing Tuple with R_dest_addr = TR_to_orig_addr, then
create an unused Routing Tuple with:
R_dest_addr := TR_to_orig_addr;R_next_iface_addr := R_next_iface_addr of the current Routing Tuple;R_local_iface_addr := R_local_iface_addr of the current Routing Tuple;R_metric := new_metric;R_dist := new_dist.
Otherwise, if there is an unused Routing Tuple with R_dest_addr = TR_to_orig_addr,
and either new_metric < R_metric or (new_metric = R_metric and the updated
Routing Tuple would be preferred), then update this Routing Tuple to have:
R_next_iface_addr := R_next_iface_addr of the current Routing Tuple;R_local_iface_addr := R_local_iface_addr of the current Routing Tuple;R_metric := new_metric;R_dist := new_dist.
The following procedure is executed once.
For each Neighbor Tuple with N_symmetric = true and N_out_metric != UNKNOWN_METRIC:
For each network address (the "neighbor address") in N_neighbor_addr_list,
if the neighbor address is not equal to the R_dest_addr of any Routing Tuple,
then add a new Routing Tuple, with:
R_dest_addr := neighbor address;R_next_iface_addr := selected link address for the neighbor address;R_local_iface_addr := selected local address for the neighbor address;R_metric := N_out_metric;R_dist := 1.
The following procedure is executed once.
For each Routable Address Topology Tuple, if:
TA_dest_addr is not equal to the R_dest_addr of any Routing Tuple
added in an earlier stage; AND
TA_from_orig_addr is equal to the R_dest_addr of a Routing Tuple
(the "previous Routing Tuple"),
then add a new Routing Tuple, with:
R_dest_addr := TA_dest_addr;R_next_iface_addr := R_next_iface_addr of the previous Routing Tuple;R_local_iface_addr := R_local_iface_addr of the previous Routing Tuple;R_metric := R_metric of the previous Routing Tuple + TA_metric;R_dist := R_dist of the previous Routing Tuple + 1.
There may be more than one Routing Tuple that may be added for an
R_dest_addr in this stage. If so, then for each such
R_dest_addr, a Routing Tuple with minimum R_metric MUST be
added; otherwise, a Routing Tuple that is preferred SHOULD be
added.
The following procedure is executed once.
For each Attached Network Tuple, if:
AN_net_addr is not equal to the R_dest_addr of any Routing Tuple
added in an earlier stage; AND
AN_orig_addr is equal to the R_dest_addr of a Routing Tuple
(the "previous Routing Tuple),
then add a new Routing Tuple, with:
R_dest_addr := AN_net_addr;R_next_iface_addr := R_next_iface_addr of the previous Routing Tuple;R_local_iface_addr := R_local_iface_addr of the previous Routing Tuple;R_metric := R_metric of the previous Routing Tuple + AN_metric;R_dist := R_dist of the previous Routing Tuple + AN_dist.
There may be more than one Routing Tuple that may be added for an
R_dest_addr in this stage. If so, then for each such
R_dest_addr, a Routing Tuple with minimum R_metric MUST be
added; otherwise, a Routing Tuple that is preferred SHOULD be
added.
The following procedure is OPTIONAL according to and MAY be
executed once.
For each 2-Hop Tuple with N2_out_metric != UNKNOWN_METRIC, if:
N2_2hop_addr is a routable address; AND
N2_2hop_addr is not equal to the R_dest_addr of any Routing Tuple
added in an earlier stage; AND
the Routing Tuple with R_dest_addr = N_orig_addr of the corresponding
Neighbor Tuple (the "previous Routing Tuple") has R_dist = 1,
then add a new Routing Tuple, with:
R_dest_addr := N2_2hop_addr;R_next_iface_addr := R_next_iface_addr of the previous Routing Tuple;R_local_iface_addr := R_local_iface_addr of the previous Routing Tuple;R_metric := R_metric of the previous Routing Tuple + N_out_metric
of the corresponding Neighbor Tuple;R_dist := 2.
There may be more than one Routing Tuple that may be added for an
R_dest_addr in this stage. If so, then for each such
R_dest_addr, a Routing Tuple with minimum R_metric MUST be
added; otherwise, a Routing Tuple that is preferred SHOULD be
added.
TC messages are instances of messages. This
specification requires that TC messages contain <msg-hop-limit>
and <msg-orig-addr> fields. It supports TC messages with any
combination of remaining message header options and address encodings
enabled by that convey the required information.
As a consequence, there is no single way to represent how all TC messages
look. This appendix illustrates a TC message; the exact values and content
included are explained in the following text.
The TC message's four-bit Message Flags (MF) field has a value of 15,
indicating that the message header contains originator address, hop limit,
hop count, and message sequence number fields. Its four-bit Message Address
Length (MAL) field has value 3, indicating addresses in the message have a
length of four octets, here being IPv4 addresses. The overall message length
is 75 octets.
The message has a Message TLV Block with a content length of 17 octets containing
four TLVs. The first two TLVs are validity and interval times for the message.
The third TLV is the content sequence number TLV used to carry the 2-octet ANSN
and (with default type extension zero, i.e., COMPLETE) indicates that the
TC message is complete. The fourth TLV contains forwarding and routing
willingness values for the originating router (FWILL and RWILL, respectively).
Each TLV uses a TLV with Flags octet (MTLVF) value 16,
indicating that it has a Value, but no type extension or start and stop indexes.
The first two TLVs have a Value Length of 1 octet; the last has a Value Length
of 2 octets.
The message has two Address Blocks. (This is not necessary. The
information could be conveyed using a single Address Block; the
use of two Address Blocks, which is also allowed, is illustrative
only.) The first Address Block contains 3 addresses, with Flags
octet (ABF) value 128, hence with a Head section (with length 2
octets) but no Tail section and with Mid sections with length
two octets. The following TLV Block (content length 13 octets) contains
two TLVs. The first TLV is a NBR_ADDR_TYPE TLV with Flags octet (ATLVF)
value 16, indicating a single Value but no indexes. Thus, all these
addresses are associated with the Value (with Value Length 1 octet)
ROUTABLE_ORIG, i.e., they are originator addresses of advertised
neighbors that are also routable addresses. The second TLV is a
LINK_METRIC TLV with Flags octet (ATLVF) value 20, indicating a
Value for each address, i.e., as the total Value Length is 6 octets,
each address is associated with a Value with length two octets.
These Value fields are each shown as having four bits
indicating that they are outgoing neighbor metric values and as
having twelve bits that represent the metric value (the first four
bits being the exponent, the remaining eight bits the mantissa).
The second Address Block contains 1 address, with Flags octet (ATLVF)
176, indicating that there is a Head section (with length 2 octets),
that the Tail section (with length 2 octets) consists of zero valued
octets (not included), and that there is a single prefix length, which is
16. The network address is thus Head.0.0/16. The following TLV Block
(content length 9 octets) includes two TLVs. The first has a Flags
octet (ATLVF) of 16, again indicating that no indexes are needed, but
that a Value (with Value Length 1 octet) is present, indicating the
address distance as a number of hops. The second TLV is another
LINK_METRIC TLV, as in the first Address TLV Block except with a Flags
octet (ATLVF) value 16, indicating that a single Value is present.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TC | MF=15 | MAL=3 | Message Length = 75 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Limit | Hop Count | Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message TLV Block Length = 17 | VALIDITY_TIME | MTLVF = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value Len = 1 | Value (Time) | INTERVAL_TIME | MTLVF = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value Len = 1 | Value (Time) | CONT_SEQ_NUM | MTLVF = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value Len = 2 | Value (ANSN) | MPR_WILLING |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTLVF = 16 | Value Len = 1 | FWILL | RWILL | Num Addrs = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ABF = 128 | Head Len = 2 | Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid | Address TLV Block Length = 13 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NBR_ADDR_TYPE | ATLVF = 16 | Value Len = 1 | ROUTABLE_ORIG |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LINK_METRIC | ATLVF = 20 | Value Len = 6 |0|0|0|1|Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric (cont) |0|0|0|1| Metric |0|0|0|1|Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric (cont) | Num Addrs = 1 | ABF = 176 | Head Len = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head | Tail Len = 2 | Pref Len = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address TLV Block Length = 9 | GATEWAY | ATLVF = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value Len = 1 | Value (Hops) | LINK_METRIC | ATLVF = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value Len = 2 |0|0|0|1| Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Due to its proactive nature, this protocol has a natural control
over the flow of its control traffic. Routers transmit control
messages at predetermined rates specified and bounded by message intervals.
This protocol employs for local signaling, embedding
MPR selection advertisement through a simple Address Block TLV and router
willingness advertisement (if any) as a single Message TLV. Local
signaling, therefore, shares the characteristics and constraints of
.
Furthermore, the use of MPRs can greatly reduce the signaling overhead
from link state information dissemination in two ways, attaining both
flooding reduction and topology reduction. First, using MPR flooding,
the cost of distributing link state information throughout the network
is reduced, as compared to when using blind flooding, since only MPRs
need to forward link state declaration messages. Second, the amount
of link state information for a router to declare is reduced; it only needs
to contain that router's MPR selectors. This reduces the size of a
link state declaration as compared to declaring full link state information.
In particular, some routers may not need to declare any such information.
In dense networks, the reduction of control traffic can be of several
orders of magnitude compared to routing protocols using blind
flooding . This feature naturally provides more
bandwidth for useful data traffic and further pushes the frontier of
congestion.
Since the control traffic is continuous and periodic, it keeps the quality
of the links used in routing more stable. However, using some options,
some control messages (HELLO messages or TC messages) may be intentionally
sent in advance of their deadline in order to increase the responsiveness
of the protocol to topology changes. This may cause a small, temporary, and
local increase of control traffic; however, this is at all times bounded by
the use of minimum message intervals.
A router that recognizes that the network is suffering from congestion can
increase its message interval parameters. If this is done by most or all
routers in the network, then the overall control traffic in the network will be reduced.
When using this capability, routers will have to take care not to increase
message interval parameters such that they cannot cope with network
topology changes. Note that routers can make such decisions independently;
it is not necessary for all routers to be using the same parameter values, nor is it necessary that all routers decide to change their intervals at the same time.