The Session Initiation Protocol (SIP) and Session Description Protocol (SDP) Static Dictionary for Signaling Compression (SigComp)
RFC 3485
| Document | Type |
RFC - Proposed Standard
(March 2003; No errata)
Updated by RFC 4896
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Stream | WG state | WG Document | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 3485 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Allison Mankin | ||
| Send notices to | <rohan@cisco.com>, <dean.willis@softarmor.com> | ||
Network Working Group M. Garcia-Martin
Request for Comments: 3485 Ericsson
Category: Standards Track C. Bormann
J. Ott
TZI/Uni Bremen
R. Price
Siemens/Roke Manor
A. B. Roach
dynamicsoft
February 2003
The Session Initiation Protocol (SIP) and Session Description Protocol
(SDP) Static Dictionary for Signaling Compression (SigComp)
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 (2003). All Rights Reserved.
Abstract
The Session Initiation Protocol (SIP) is a text-based protocol for
initiating and managing communication sessions. The protocol can be
compressed by using Signaling Compression (SigComp). Similarly, the
Session Description Protocol (SDP) is a text-based protocol intended
for describing multimedia sessions for the purposes of session
announcement, session invitation, and other forms of multimedia
session initiation. This memo defines the SIP/SDP-specific static
dictionary that SigComp may use in order to achieve higher
efficiency. The dictionary is compression algorithm independent.
Garcia-Martin, et al. Standards Track [Page 1]
RFC 3485 SIP and SDP Static Dictionary for SigComp February 2003
Table of Contents
1. Introduction.....................................................2
2. Design considerations............................................3
3. Binary representation of the SIP/SDP dictionary..................5
4. Security Considerations.........................................13
5. IANA Considerations.............................................13
6. Acknowledgements................................................14
7. References......................................................14
7.1 Normative References........................................14
7.2 Informative References......................................14
Appendix A. SIP input strings to the SIP/SDP static dictionary.....17
Appendix B. SDP input strings to the SIP/SDP static dictionary.....26
Authors' Addresses.................................................29
Full Copyright Statement...........................................30
1. Introduction
SIP [3] and SDP [24] are text-based protocols that use the UTF-8
charset (RFC 2279 [5]). SIP and SDP were designed for rich bandwidth
links. However, when SIP/SDP is run over narrow bandwidth links,
such as radio interfaces or low speed serial links, the session setup
time increases substantially, compared to an operation over a rich
bandwidth link.
The session setup time can decrease dramatically if the SIP/SDP
signaling is compressed. The signaling compression mechanisms
specified in SigComp [1] provide a multiple compression/decompression
algorithm framework to compress and decompress text-based protocols
such as SIP and SDP.
When compression is used in SIP/SDP, the compression achieves its
maximum rate once a few message exchanges have taken place. This is
due to the fact that the first message the compressor sends to the
decompressor is only partially compressed, as there is not a previous
stored state to compress against. As the goal is to reduce the
session setup time as much as possible, it seems sensible to
investigate a mechanism to boost the compression rate from the first
message.
In this memo we introduce the static dictionary for SIP and SDP. The
dictionary is to be used in conjunction with SIP, SDP and SigComp.
The static SIP/SDP dictionary constitutes a SigComp state that can be
referenced in the first SIP message that the compressor sends out.
Garcia-Martin, et al. Standards Track [Page 2]
RFC 3485 SIP and SDP Static Dictionary for SigComp February 2003
2. Design considerations
The static SIP/SDP dictionary is a collection of well-known strings
that appear in most of the SIP and SDP messages. The dictionary is
not a comprehensive list of reserved words, but it includes many of
the strings that appear in SIP and SDP signaling.
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