Signaling Compression (SigComp) Corrections and Clarifications
RFC 4896
| Document | Type | RFC - Proposed Standard (June 2007; No errata) | |
|---|---|---|---|
| Authors | Adam Roach , Abigail Surtees , Mark West | ||
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4896 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Magnus Westerlund | ||
| Send notices to | (None) | ||
Network Working Group A. Surtees
Request for Comments: 4896 M. West
Updates: 3320, 3321, 3485 Siemens/Roke Manor Research
Category: Standards Track A.B. Roach
Estacado Systems
June 2007
Signaling Compression (SigComp) Corrections and Clarifications
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 IETF Trust (2007).
Abstract
This document describes common misinterpretations and some
ambiguities in the Signaling Compression Protocol (SigComp), and
offers guidance to developers to resolve any resultant problems.
SigComp defines a scheme for compressing messages generated by
application protocols such as the Session Initiation Protocol (SIP).
This document updates the following RFCs: RFC 3320, RFC 3321, and RFC
3485.
Surtees, et al. Standards Track [Page 1]
RFC 4896 SigComp Corrections and Clarifications June 2007
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Decompression Memory Size . . . . . . . . . . . . . . . . . . 3
2.1. Bytecode within Decompression Memory Size . . . . . . . . 3
2.2. Default Decompression Memory Size . . . . . . . . . . . . 4
3. UDVM Instructions . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Data Input Instructions . . . . . . . . . . . . . . . . . 5
3.2. MULTILOAD . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. STATE-FREE . . . . . . . . . . . . . . . . . . . . . . . . 6
3.4. Using the Stack . . . . . . . . . . . . . . . . . . . . . 6
4. Byte Copying Rules . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Instructions That Use Byte Copying Rules . . . . . . . . . 9
5. State Retention Priority . . . . . . . . . . . . . . . . . . . 9
5.1. Priority Values . . . . . . . . . . . . . . . . . . . . . 9
5.2. Multiple State Retention Priorities . . . . . . . . . . . 10
5.3. Retention Priority 65535 (or -1) . . . . . . . . . . . . . 10
6. Duplicate State . . . . . . . . . . . . . . . . . . . . . . . 14
7. State Identifier Clashes . . . . . . . . . . . . . . . . . . . 14
8. Message Misordering . . . . . . . . . . . . . . . . . . . . . 15
9. Requested Feedback . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Feedback When SMS Is Zero . . . . . . . . . . . . . . . . 15
9.2. Updating Feedback Requests . . . . . . . . . . . . . . . . 16
10. Advertising Resources . . . . . . . . . . . . . . . . . . . . 16
10.1. The I-bit and Local State Items . . . . . . . . . . . . . 16
10.2. Dynamic Update of Resources . . . . . . . . . . . . . . . 17
10.3. Advertisement of Locally Available State Items . . . . . . 17
10.3.1. Basic SigComp . . . . . . . . . . . . . . . . . . . . 18
10.3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . 18
10.3.3. SigComp Extended Mechanisms . . . . . . . . . . . . . 19
11. Uncompressed Bytecode . . . . . . . . . . . . . . . . . . . . 19
12. RFC 3485 SIP/SDP Static Dictionary . . . . . . . . . . . . . . 20
13. Security Considerations . . . . . . . . . . . . . . . . . . . 21
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22
16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
16.1. Normative References . . . . . . . . . . . . . . . . . . . 23
16.2. Informative References . . . . . . . . . . . . . . . . . . 23
Appendix A. Dummy Application Protocol (DAP) . . . . . . . . . . 24
A.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 24
A.2. Processing a DAP Message . . . . . . . . . . . . . . . . . 24
A.3. DAP Message Format in ABNF . . . . . . . . . . . . . . . . 26
A.4. An Example of a DAP Message . . . . . . . . . . . . . . . 26
Surtees, et al. Standards Track [Page 2]
RFC 4896 SigComp Corrections and Clarifications June 2007
1. Introduction
SigComp [1] defines the Universal Decompressor Virtual Machine (UDVM)
for decompressing messages sent by a compliant compressor. SigComp
further describes mechanisms to deal with state handling, message
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