Research in Motion 5000 Riverside Drive, Building 6, Suite 100 Irving, Texas 75039 USA jbakker@blackberry.comPolycom Technology India Pvt Ltd Manyata Embassy Business Park, Bangalore 560045 India ranjit.avasarala@polycom.comDISPATCH 3GPP and TISPAN are defining the protocol specification for the
Communication Diversion (CDIV) service using IP Multimedia (IM) Core
Network (CN) subsystem (IMS) supplementary service. As part of CDIV, a SIP
based event package is used for notifying users about
diversions (re-directions or forwarding) of requests for
communication sessions targetting the user. This document defines
the SIP event package to support subscription and notification of
diversions. The proposed event package is
applicable to the CDIV supplementary service in IMS and may not be
applicable to the general internet.
3GPP is currently maintaining and specifying communication diversion
mechanisms which allow users to forward and/or redirect incoming
communications to other destinations. A common
example is Communication Forward On Busy (CFB) wherein users can instruct a server in the network to
redirect incoming requests, whilst they are participating in a session.
Similarly, other variants of communication diversion are well defined
and used in practice such as Communication Forward on subscriber Not Reachable
(CFNRc), Communication Forward Unconditional (CFU), Communication Forwarding No Reply (CFNR),
Communication Deflection (CD), and Communication Forwarding on Not Logged-in (CFNL). 3GPP is
currently maintaining and specifying a mechanism for users to
configure Communication Diversion Services (3GPP TS 24.604 ) for their
incoming communications.
The mechanism for users to configure Communication Diversion Services (3GPP TS 24.604 ) may cause a variety of rules
to be provisioned in the network at the same time. For instance, a
user may have, in addition to other communication diversion rules,
various CDIV services configured, e.g. some rules based on the
time-of-the-day and some rules based on the calling party's identity.
It is possible that the user loses track of the various rules and
undesirable diversions may occur. If the user cann't notified of the diversions,
then it is hard for the user to determine that the combination of rules have
caused undesirable diversions.
CDIV Notification (CDIVN) is a CDIV service providing the user the capability to
receive notifications about all diverted communications (CFU, CFB, CFNR, CD, CFNRc and CFNL).
If CDIVN is configured, when a communication is diverted on behalf of the subscriber, the Subcsriber receives a notification.
The subscriber is then in able to determine whether the communication diversion
which just occurred, was indeed as per their expectation. For example,
a subscriber intended to divert all incoming calls to voice-mail,
between 3.00 p.m. to 4.00 p.m. Yet, by mistake she configures the
time-duration as 3.00 to 4.00 p.m. It would be very difficult for
her to spot this error while manually reviewing her complete set of
communication diversion services, with their various configurations.
Instead, if the subscriber receives a real-time notification of any
communication diversion occurring after 4 p.m., she would be able to
immediately guess that something is 'wrong' or not as per her
intention and take corrective action. Such corrective action could
be manual verification of the specific rule which triggered the
communication diversion, wherein she will be able to spot the
"mistake" more easily.
Thus, for effective subscriber services management of multiple
configurations of various Communication Diversion services, a
notification-based mechanism may work well. Such a mechanism would
involve notifying subscribers about diversions of their incoming
communications, as and when the communication diversion happens or
with a slight delay (as per subscriber service configuration). As
such diversion-related information is conveyed almost instantly or
within a small time-frame, the subscribers can verify whether the
particular communication diversion is indeed correct at that instant
of time.
This document defines a SIP event package that allows a SIP User
Agents to subscribe to and be notified of communication diversions
enacted on their behalf using the CDIV service. The protocol specification for the
CDIV service (using IMS core networks) can be found in 3GPP TS 24.604 .
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119
and indicate requirement levels for compliant implementations. It is believed that the SIP event package defined here is not applicable to the general Internet; it has been designed to serve the
architecture of the CDIV service (see 3GPP TS 24.604 ) in IMS core networks
3GPP TS 24.229 (see ). The aim of this memo is to follow the procedure indicated in RFC 5727.
and to register a new event package with event name "comm-div-info" with IANA.
CDIV: Communication Diversion. CDIVN: Communication Diversion Notification. TISPAN: Telecommunications and Internet Converged Services and Protocols for Advanced Networking. Subscriber - The User Agent who has subscribed to the Communication diversion notification service. User - Another term for the subscriber. Diverting User - The User Agent who has configured a Communication Diversion. This could be the User Agent who has configured
the CDIV service rules in the network, in accordance with 3GPP TS 24.604 . Diverted-To Entity/User - The User Agent who is the new target
of the incoming communication, post execution of any configured CDIV service rules. Originating User - The User Agent who is the originator of the incoming communication, which was initially
targeted towards the Diverting User, but finally sent to the Diverted-To User. The Originating
User is also referred to as the Caller. IMS Core Network - This refers to the IMS based SIP based network that conforms to the
and not the general SIP network as defined in .The CDIVN service enables a user to receive notification about the diversion of any of his/her incoming
communications, which were addressed to the user's address. A comprehensive description of all the requirements that affect the
CDIVN service developed by 3GPP and TIPSAN is found in and .
This section fills in the details needed for an event package as defined in Section 4.4 of . The SIP Events specification requires package definitions to specify the name of their package or template-package.
The name of this package is "comm-div-info". As specified in , this value appears in the Event
header present in SUBSCRIBE and NOTIFY requests. The SIP Events specification allows packages to define additional parameters. This event package
"comm-div-info" does not define additional parameters.
The SIP Events specification requires package or template-package definitions to define the usage,
if any, of message bodies in SUBSCRIBE requests. Furthermore, the SIP Events specification requires that message bodies are specified or that
detailed specifications for the syntax and semantics of such a message body are cited.
A SUBSCRIBE for Communication Diversion event MAY contain a message body. The purpose of the body depends on its type. Subscriptions to
the Comm-div-info event package SHALL only include a message body of MIME type "application/vnd.3gpp.comm-div-info+xml". The syntax and
semantics of the message body can be found in 3GPP TS 24.604 .
A body of the SUBSCRIBE request with content type set to MIME type
"application/comm-div-info-filter+xml" contains information about the
communication diversion notification information filter criteria and
notification trigger criteria. The subscriber SHALL also verify that
this information conforms to a valid XML document as defined in [11].
The subscriber SHALL also verify that the information contained in
the XML document contains elements defined in .
The default expiration time for subscriptions within this package is 3600 seconds.
As per , the subscriber
MAY specify an alternate expiration in the Expires header field.
The SIP Events specification requires package definitions to define a default value for subscription durations, and to discuss
reasonable choices for durations when they are explicitly specified.
The NOTIFY message contains an event body. This event body is in a format listed in the Accept header field of the SUBSCRIBE request
or a package specific default format if the Accept header field was omitted from the SUBSCRIBE request.
Furthermore, the SIP Events specification requires that event bodies are specified or that detailed specifications for the
syntax and semantics of such a event body are cited.
In this event package, the body of the notification contains the communication diversion information pertaining to the diversion
that occurred in the network on behalf of the subscriber. The package specific body has the MIME type
"application/vnd.3gpp.comm-div-info+xml". The syntax and semantics of the event body can be found in
3GPP TS 24.604 .
A subscriber must
always Accept receiving a NOTIFY with Content-Type "application/vnd.3gpp.comm-div-info+xml". The notifiers MUST be capable of accepting
the "application/vnd.3gpp.comm-div-info+xml" data format as described in 3GPP TS 24.604 . If the notifier
sends a NOTIFY, it MUST include contents according to 3GPP TS 24.604 and include the
content-type header field set to "application/vnd.3gpp.comm-div-info+xml".
The default Accept header field for SUBSCRIBE is "application/vnd.3gpp.comm-div-info+xml" (assuming Event header has a value of "comm-div-info-ntfy").
The contents of a "application/vnd.3gpp.comm-div-info+xml" XML document in a NOTIFY request can contain sensitive information
that can reveal some privacy
information. Therefore, such documents MUST only be sent to authorized subscribers. In order to determine if a
subscription originates in an authorized user, the subscriber MUST be authenticated as described in
and then the user MUST be authorized to be a subscriber as described in .
The Notifier MUST check if the SUBSCRIBE request contains a body part. If there is a body part, the Notifier MUST do the following.
Check if a SUBSCRIBE request body part conforms to "application/vnd.3gpp.comm-div-info+xml" XML Schema document in 3GPP TS 24.604 .
If it conforms then the Notifier processes the document and generates notifications accordingly.
Notifiers MUST authenticate all subscription requests. This authentication can be done using any of the mechanisms defined in
and other authentication extensions.
Once authenticated, the notifier makes an authorization decision. A notifier MUST NOT accept a subscription unless
authorization has been provided by the user. The means by which authorization are provided are outside the scope of this document.
The SIP Events specification details the formatting and structure of NOTIFY messages. However, packages are mandated to provide
detailed information on when to send a NOTIFY, how to compute the state of the resource, how to generate neutral or fake state information,
and whether state information is complete or partial. This section describes those details for the "comm-div-info" event package.
A notifier sends a NOTIFY request when a communication diversion is enacted on behalf of the user. If there is a stored filter criteria for
the user, then the notifier MUST look into the filter criteria. If the filter criteria
matches, then the notifier generates a NOTIFY request and sends the NOTIFY request to the user. If the filter criteria do not
match, then the notifier does not generate a NOTIFY request. A body part of the NOTIFY has a
content-type set to "application/vnd.3gpp.comm-div-info+xml" and must contain the elements defined in 3GPP TS 24.604 .
Notifiers could detect that a communication diversion was enacted on behalf of the subscriber via a "History-Info" header field value, per 3GPP TS 24.604 , sent from an application server hosting the CDIV service.
The SIP Events specification expects event packages to describe the process followed by the subscriber upon receipt of a
NOTIFY request. In this specification, each NOTIFY request contains a XML document for the content type "application/vnd.3gpp.comm-div-info+xml" (see 3GPP TS 24.604 ).
The SIP Events specification requires each package to describe handling of forked Requests.
This specification only allows a single dialog to be constructed as a result of emitting an initial SUBSCRIBE request. This
guarantees that only a single notifier is generating notifications for a particular subscription to a particular user.
But if forking is allowed, then the server that receives multiple subscriptions should be able to generate a single dialog on behalf of all the
subscriptions that are received. Any subsequent subscriptions should be mapped to the generated dialog. Similarly when the server
receives a single notification for the generated dialog, it should be generate the corresponding number of notifications towards the
received notifications.
The SIP Events specification requires each package to specify maximum rate at which notifications can be sent .
Comm-div-info notifiers SHOULD NOT generate notifications for a single subscription at a rate of more than once every five seconds.
An FSM associated with the subscriber is created in the "IDLE" state, e.g. upon receiving filter criteria. Whenever
a communication diversion is detected for a URI of the subscriber, a state transition occurs. Depending on whether a
filter is matched, a state is entered. In the DIVERSION_NOTIFIED state, notification information is sent to the subscriber.
If notification information needs to be sent, the Notifier generates the notification information and sends the information
to the subscriber. If a diversion is detected but no filter is matched, a transition to DIVERSION_NOT_NOTIFIED occurs.
The FSM for CDIVN is shown in below Figure.
+ |
| NOT | | | DIVERSION |
| NOTIFIED +--+ +--+ NOTIFIED |
+-----+-----+ | +-------+-------+
^ | |
+--------+----------------------------+
Next diversion & No filter(s) match
]]>
The subscriber could receive, as part of the notification information, the
state the FSM was in prior to detecting the diversion.
[IDLE]: meaning that no diversions have occured since setting the present
"filter".[DIVERSION_NOTIFIED]: meaning that since receiving the last NOTIFY request
for this even package, no additional diversions have occured. [DIVERSION_NOT_NOTIFIED]: meaning that one or more diversions have occured since setting the present
"filter" or since receiving the last NOTIFY request for this even package. Comm-div-info document is an XML document that MUST be well-formed
and SHOULD be valid. Communication Diversion Information documents MUST be based on XML 1.0 and MUST be encoded using UTF-8
. The
structure of the filter and notifier format;examples of the use of subscribtion and notification bodies; andXML Schema of subscribtion and notification bodies,
have been described in 3GPP TS 24.604 .
Authentication and authorization of subscriptions have been discussed
in . Lack of authentication or authorization may provide
comm-div-info information to unauthorized parties and can reveal
sensitive information with regards to the user's call receiving
patterns. For example, who calls the user and at what time, etc.
Integrity protection and confidentiality of notifications are also
discussed in . If a notifier does not encrypt bodies of
NOTIFY requests, an eavesdropper could learn the status of a SIP user
agent and use it to create malicious sessions. If the notifier
does not integrity protect the bodies of NOTIFY requests, a man-in-
the-middle attacker or malicious SIP proxy could modify the contents
of the comm-div-info event package notification. Although this does
not cause harm, it can create annoyances. This document registers the new SIP Event Package.
Published Specification: RFC XXXX (Note to RFC Editor)
]]>
The authors would like to thank Mary Barnes, Samir Saklikar, Subir Saha, Ban Al-Bakri, Roland Jesske, Jose Miguel Torres,
Paul Kyzivat, John Elwell , Keith Drage , Gonzalo Camarillo, Olle E. Johansson, Atle Monrad and Dean Willis for their valuable comments and suggestions. Changes from draft-avasarala-dispatch-comm-div-notification-10
The SIP Events specification (RFC 3265) requires that bodies to be used as part of the event package are specified or that
detailed specifications for the syntax and semantics of such a body are cited. With that knowledge, the authors could greatly reduce the size of this draft; the
detailed specification is in 3GPP TS 24.604.Editorial clean up.Changes from draft-avasarala-dispatch-comm-div-notification-09
No changes of substance. An update addressing the comments on the list and offline, will follow.Changes from draft-avasarala-dispatch-comm-div-notification-08
Corrected text to not preclude use of S/MIME or multipart.Updated Finite State Machine diagram.Updated the schema for CDIVN notification document to reflect FSM updates. Changes from draft-avasarala-dispatch-comm-div-notification-07
Added MIME type for communication diversion filter criteria.Updated the State Agents section to add state diagram for CDIVN Service.Updated the schema for CDIVN notification document. Updated the Acknowledgements section.Changes from draft-avasarala-dispatch-comm-div-notification-06
Changed the namespace for XML schema to "http://urn.etsi.org" aligning with 3GPP TS 24.504Updated the XML schema and removed the word "optional" for "diverting-user-info" Changes from draft-avasarala-dispatch-comm-div-notification-05
Updated Requirements section Incorporated expert review comments for state information, notification content and subscribe bodies Modified the section on examples for subscription and notification body Changes from draft-avasarala-dispatch-comm-div-notification-04
Incorporated review comments Added text for SUBSCRIBE body and NOTIFY body and checking of
filter criteria. Updated Communication Diversion Notification Information document
and XML schema to add Diversion and notification count information as optional parameters.Changes from draft-avasarala-dispatch-comm-div-notification-03
Added State information to Notifiers. Modified diverting-URI definition and element in communication
diversion information selection criteria as optional parameter
. Changes from draft-avasarala-dispatch-comm-div-notification-02
Modified the applicability statement to make it more IMS specific. Added a definition for IMS Core network. Updated authors list and Acknowledgement sections. Changes from draft-avasarala-dispatch-comm-div-notification-01
Incorporated review comments. Modified contact details for co author Subir Saha. Changes from draft-avasarala-sipping-comm-div-notification-00
Changed contact details of co author Subir Saha. Moved from SIPPING to DISPATCH WG. Changes from draft-avasarala-dispatch-comm-div-notification-00
Added comm-div-info document structure information and schema for the
event package.
Added more elaborate description for various sections in comm-div-info
document