Usage of the Session Description Protocol (SDP) Alternative Network Address Types (ANAT) Semantics in the Session Initiation Protocol (SIP)
RFC 4092
| Document | Type |
RFC - Proposed Standard
(June 2005; No errata)
Obsoleted by RFC 5245
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | WG Document | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4092 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Allison Mankin | ||
| Send notices to | rohan@ekabal.com | ||
Network Working Group G. Camarillo
Request for Comments: 4092 Ericsson
Category: Standards Track J. Rosenberg
Cisco Systems
June 2005
Usage of the Session Description Protocol (SDP)
Alternative Network Address Types (ANAT) Semantics
in the Session Initiation Protocol (SIP)
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes how to use the Alternative Network Address
Types (ANAT) semantics of the Session Description Protocol (SDP)
grouping framework in SIP. In particular, we define the sdp-anat SIP
option-tag. This SIP option-tag ensures that SDP session
descriptions that use ANAT are only handled by SIP entities with ANAT
support. To justify the need for such a SIP option-tag, we describe
what could possibly happen if an ANAT-unaware SIP entity tried to
handle media lines grouped with ANAT.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. The sdp-anat Option-Tag . . . . . . . . . . . . . . . . . . . . 2
4. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 3
4.1. Answerer Supports All the Network Types Offered . . . . 3
4.2. Answerer Does Not Support All the Network Types Offered. 3
4.3. OPTIONS Requests . . . . . . . . . . . . . . . . . . . . 4
5. Option-Tag Usage . . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Camarillo & Rosenberg Standards Track [Page 1]
RFC 4092 ANAT Usage in SDP June 2005
1. Introduction
SIP [3] UAs (User Agents) often support different network address
types. For example, a UA may have an IPv6 address and an IPv4
address. Such a UA will typically be willing to use any of its
addresses to establish a media session with a remote UA. If the
remote UA only supports IPv6, for instance, both UAs will use IPv6 to
send and receive media.
The Alternative Network Address Types (ANAT) semantics [7] of the SDP
[2] grouping framework [5] allow UAs to offer [4] alternative
addresses of different types in an SDP session description. The
IPv4/IPv6 dual-stack SIP UA of our previous example would generate an
offer grouping an IPv6 media line and an IPv4 media line using ANAT.
Upon receipt of this offer, the answerer [4] would accept one media
line and reject the other.
If the recipient of an offer that uses ANAT supports the ANAT
semantics, everything works as described in the ANAT specification
[7]. Nevertheless, the recipient of such an offer (i.e., the
answerer) may not support ANAT. In this case, different
implementations of the answerer would react in different ways. This
document discusses the answerer's behaviors that are most likely to
be found and describes their consequences. To avoid these
consequences, we define the sdp-anat SIP option-tag.
The sdp-anat option-tag can be used to ensure that an offer using
ANAT is not processed by answerers without support for ANAT. This
option-tag can also be used to explicitly discover the capabilities
of a UA (i.e., whether it supports ANAT).
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [1] and indicate requirement levels for
compliant implementations.
3. The sdp-anat Option-Tag
We define the option-tag sdp-anat for use in the Require and
Supported SIP [3] header fields. SIP user agents that place this
option-tag in a Supported header field understand the ANAT semantics
Show full document text