Internet Engineering Task Force (IETF) G. Pelletier
Request for Comments: 6846 InterDigital Communications
Obsoletes: 4996 K. Sandlund
Category: Standards Track Ericsson
ISSN: 2070-1721 L-E. Jonsson
M. West
Siemens/Roke Manor
January 2013
RObust Header Compression (ROHC):
A Profile for TCP/IP (ROHC-TCP)
Abstract
This document specifies a RObust Header Compression (ROHC) profile
for compression of TCP/IP packets. The profile, called ROHC-TCP,
provides efficient and robust compression of TCP headers, including
frequently used TCP options such as selective acknowledgments (SACKs)
and Timestamps.
ROHC-TCP works well when used over links with significant error rates
and long round-trip times. For many bandwidth-limited links where
header compression is essential, such characteristics are common.
This specification obsoletes RFC 4996. It fixes a technical issue
with the SACK compression and clarifies other compression methods
used.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6846.
Pelletier, et al. Standards Track [Page 1]RFC 6846 ROHC-TCP January 2013Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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described in the Simplified BSD License.
Pelletier, et al. Standards Track [Page 2]RFC 6846 ROHC-TCP January 2013Table of Contents
1. Introduction ....................................................5
2. Terminology .....................................................5
3. Background ......................................................7
3.1. Existing TCP/IP Header Compression Schemes .................7
3.2. Classification of TCP/IP Header Fields .....................8
4. Overview of the TCP/IP Profile (Informative) ...................10
4.1. General Concepts ..........................................10
4.2. Compressor and Decompressor Interactions ..................10
4.2.1. Compressor Operation ...............................10
4.2.2. Decompressor Feedback ..............................11
4.3. Packet Formats and Encoding Methods .......................11
4.3.1. Compressing TCP Options ............................11
4.3.2. Compressing Extension Headers ......................11
4.4. Expected Compression Ratios with ROHC-TCP .................12
5. Compressor and Decompressor Logic (Normative) ..................13
5.1. Context Initialization ....................................13
5.2. Compressor Operation ......................................13
5.2.1. Compression Logic ..................................13
5.2.1.1. Optimistic Approach .......................14
5.2.1.2. Periodic Context Refreshes ................14
5.2.2. Feedback Logic .....................................14
5.2.2.1. Optional Acknowledgments (ACKs) ...........14
5.2.2.2. Negative Acknowledgments (NACKs) ..........15
5.2.3. Context Replication ................................15
5.3. Decompressor Operation ....................................16
5.3.1. Decompressor States and Logic ......................16
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