SIPCORE Working Group C. Holmberg
Internet-Draft I. Sedlacek
Intended status: Standards Track Ericsson
Expires: March 28, 2011 September 24, 2010
Indication of features supported by proxy
draft-holmberg-sipcore-proxy-feature-00.txt
Abstract
The Session Initiation Protocol (SIP) "Caller Preferences" extension
defined in RFC 3840 provides a mechanism that allows a SIP message to
convey information relating to the originator's capabilities. This
document makes it possible for SIP proxies to convey similar
information, by extending the rr-param rule defined in RFC 3261, so
that the header field parameter can be used to convey feature tags
that indicate features supported by the proxy.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on March 28, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Use-case: IMS Service Continuity . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. User Agent behavior . . . . . . . . . . . . . . . . . . . . . . 4
5. Proxy behavior . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Feature tag semantics . . . . . . . . . . . . . . . . . . . . . 4
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Example name . . . . . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 5
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
12.1. Normative References . . . . . . . . . . . . . . . . . . . 6
12.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
The SIP "Caller Preferences" extension defined in RFC 3840 [RFC3840]
provides a mechanism that allows a SIP message to convey information,
using feature tags, relating to the originator's capabilities.
Feature information can be useful for other SIP entities, that might
trigger actions and enable functions based on features supported by
other SIP entities.
This document extends the rr-param rule defined in RFC 3261
[RFC3261], so that it can be used to convey feature tags indicating
support of features in SIP proxies. The rr-param rule is used in the
SIP Path, Route, Record-Route and Service-Route header fields.
1.1. Use-case: IMS Service Continuity
The 3rd Generation Partnership Project (3GPP) defines a IP Multimedia
Subsystem (IMS) Service Continuity mechanism [3GPP.23.237] for
handover of Packet Switched (PS) sessions to Circuit Switched (CS).
The handover can be performed by a Service Centralization and
Continuity Application Server (SCC AS), or by a SCC AS together with
an Access Transfer Control Function (ATCF), that acts as a SIP proxy.
Delegating part of the session handover functionality to an ATCF
provides advantages related to voice interruption during session
handover etc, since it is located in the same network as the user.
In order for a SCC AS to delegate part of the session handover
functionality to an ATCF, when it receives a SIP REGISTER request, it
needs to be informed whether there is a proxy that provides ATCF
functionality in the registration path.
2. Conventions
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 BCP 14, RFC 2119
[RFC2119].
3. Definitions
The rr-param rule defined in RFC 3261 [RFC3261]:
rr-param = generic-param
is extended to:
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rr-param = generic-param / feature-param
where feature-param is defined in Section 9 of RFC 3840 [RFC3840].
4. User Agent behavior
This specification does not specify any new User Agent behavior.
5. Proxy behavior
When a proxy inserts a Path header field (during registration), a
Service-Route header field (during registration) or a Record-Route
header field (during a dialog establishment), it MAY insert a feature
tag in the header field.
If a feature tag is inserted in a Path or Service-Route header field
during registration, the resource identified by the URI in the header
field MUST provide support for the associated feature for all dialogs
associated with the registration, until the registration is
terminated or re-freshed.
If a feature tag is inserted in a Record-Route header field during a
dialog establishment, the resource identified by the URI in the
header field MUST provide support for the associated feature until
the dialog is terminated.
6. Feature tag semantics
The feature tag in a header field constructed using rr-param rule
indicates support of the feature in the resource identified by the
URI in the header field.
In order to insert a feature tag in a SIP header field constructed by
using rr-param rule, the feature specification MUST specify the
semantics of the feature tag when inserted in that specific header
field. Unless the feature specification defines such semantics, a
the feature tag MUST NOT be included in that specific header field.
NOTE: If a route set is built using Path, Record-Route or Service-
Route header fields, any inserted feature tag will be copied into the
associated Route header fields, together with other header field
parameters. This specification does not define any specific meaning
of the feature tags present in Route header fields in such cases.
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7. Examples
7.1. Example name
TBD
Alice P1 REGISTRAR
| | |
|--- REGISTER-------------->| |
| | |
| |--- REGISTER-------------->|
| | Path: P1;+g.3gpp.srvcc |
| | |
| | |
| |<-- 200 OK ----------------|
| | Path: P1;+g.3gpp.srvcc |
| | Service-Route: REG |
|<-- 200 OK ----------------| |
| Path: P1;+g.3gpp.srvcc | |
| Service-Route: REG | |
| | |
Figure 1: Example call flow
8. IANA Considerations
TBD
9. Security Considerations
Feature tags can provide sensitive information about a SIP entity.
RFC 3840 cautions against providing sensitive information to another
party. Once this information is given out, any use may be made of
it.
10. Acknowledgements
Thanks to Paul Kyzivat for his comments and guidance on the mailing
list.
11. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
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Changes from draft-holmberg-sipcore-proxy-feature-00
o To be added when the -01 version is submitted
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
"Indicating User Agent Capabilities in the Session
Initiation Protocol (SIP)", RFC 3840, August 2004.
12.2. Informative References
[3GPP.23.237]
3GPP, "IP Multimedia Subsystem (IMS) Service Continuity;
Stage 2", 3GPP TS 23.237 10.2.0, June 2010.
Authors' Addresses
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
Ivo Sedlacek
Ericsson
Scheelevaegen 19C
Lund 22363
Sweden
Email: ivo.sedlacek@ericsson.com
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