Network Working Group R. Price
Request for Comments: 3320 Siemens/Roke Manor
Category: Standards Track C. Bormann
TZI/Uni Bremen
J. Christoffersson
H. Hannu
Ericsson
Z. Liu
Nokia
J. Rosenberg
dynamicsoft
January 2003
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
This document defines Signaling Compression (SigComp), a solution for
compressing messages generated by application protocols such as the
Session Initiation Protocol (SIP) (RFC 3261) and the Real Time
Streaming Protocol (RTSP) (RFC 2326). The architecture and
prerequisites of SigComp are outlined, along with the format of the
SigComp message.
Decompression functionality for SigComp is provided by a Universal
Decompressor Virtual Machine (UDVM) optimized for the task of running
decompression algorithms. The UDVM can be configured to understand
the output of many well-known compressors such as DEFLATE (RFC-1951).
Price, et. al. Standards Track [Page 1]
RFC 3320 Signaling Compression (SigComp) January 2003
Table of Contents
1. Introduction...................................................2
2. Terminology....................................................3
3. SigComp architecture...........................................5
4. SigComp dispatchers...........................................15
5. SigComp compressor............................................18
6. SigComp state handler.........................................20
7. SigComp message format........................................23
8. Overview of the UDVM..........................................28
9. UDVM instruction set..........................................37
10. Security Considerations.......................................56
11. IANA Considerations...........................................58
12. Acknowledgements..............................................59
13. References....................................................59
14. Authors' Addresses............................................60
15. Full Copyright Statement......................................62
1. Introduction
Many application protocols used for multimedia communications are
text-based and engineered for bandwidth rich links. As a result the
messages have not been optimized in terms of size. For example,
typical SIP messages range from a few hundred bytes up to two
thousand bytes or more [RFC3261].
With the planned usage of these protocols in wireless handsets as
part of 2.5G and 3G cellular networks, the large message size is
problematic. With low-rate IP connectivity the transmission delays
are significant. Taking into account retransmissions, and the
multiplicity of messages that are required in some flows, call setup
and feature invocation are adversely affected. SigComp provides a
means to eliminate this problem by offering robust, lossless
compression of application messages.
This document outlines the architecture and prerequisites of the
SigComp solution, the format of the SigComp message and the Universal
Decompressor Virtual Machine (UDVM) that provides decompression
functionality.
SigComp is offered to applications as a layer between the application
and an underlying transport. The service provided is that of the
underlying transport plus compression. SigComp supports a wide range
of transports including TCP, UDP and SCTP [RFC-2960].
Price, et. al. Standards Track [Page 2]
RFC 3320 Signaling Compression (SigComp) January 2003
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