Advertising
Seamless Bidirectional Forwarding Detection (S-BFD) Discriminators in IS-ISCisco Systems510 McCarthy Blvd.Milpitas95035CAUnited Statesginsberg@cisco.comBig Switch Networksnobo.akiya.dev@gmail.comHuaweimach.chen@huawei.comThis document defines a means of advertising one or more
Seamless Bidirectional Forwarding Detection (S-BFD)
Discriminators using the IS-IS Router CAPABILITY TLV. defines a simplified mechanism for using
Bidirectional Forwarding Detection (BFD) .
This mechanism depends on network nodes knowing the BFD
Discriminators that each node in the network has reserved for this
purpose. The use of the Intermediate System to Intermediate System
(IS-IS) protocol is one possible means of
advertising these discriminators.The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119
.The IS-IS Router CAPABILITY TLV as defined in
will be used to advertise Seamless
BFD (S-BFD) Discriminators. A new sub-TLV is defined as described
below. S-BFD Discriminators sub-TLVs are formatted as specified in
.The inclusion of an S-BFD Discriminators sub-TLV in a Router
CAPABILITY TLV is optional. Multiple S-BFD Discriminators sub-TLVs MAY be
advertised by an IS. How a given discriminator is mapped to a specific
use case when multiple S-BFD Discriminators are advertised is out of
scope for this document.S-BFD Discriminator advertisements MAY be flooded within an area or
throughout the domain, using the procedures specified in
. The appropriate flooding scope depends on
the intended use of S-BFD. If S-BFD usage will be exclusively within
a Level-1 area, then area scope is appropriate. If S-BFD usage will
span different Level-1 areas, then domain scope is appropriate.IANA has added a new sub-TLV in the
"Sub&nbhy;TLVs for TLV 242" registry. The registration is as follows:Security concerns for IS-IS are addressed in ,
, and .
The new S-BFD Discriminators sub-TLV does not introduce any new
security risks for IS-IS.Advertising the S-BFD Discriminators makes it possible for
attackers to initiate S-BFD sessions using the advertised information.
The vulnerabilities this poses and how to mitigate them are discussed
in .Intermediate System to Intermediate System intra-domain routeing
information exchange protocol for use in conjunction with the protocol
for providing the connectionless-mode network service (ISO 8473)International Organization for StandardizationSeamless Bidirectional Forwarding Detection (S-BFD)The authors wish to thank Sam Aldrin, Manav Bhatia, and Carlos
Pignataro for input essential to defining the needed functionality.