RObust Header Compression (ROHC): A Profile for TCP/IP (ROHC-TCP)
RFC 4996
| Document | Type |
RFC - Proposed Standard
(July 2007; Errata)
Obsoleted by RFC 6846
Was draft-ietf-rohc-tcp (rohc WG)
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Replaces | draft-ietf-rohc-tcp-epic, draft-ietf-rohc-tcp-taroc | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4996 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Magnus Westerlund | ||
| Send notices to | (None) | ||
Network Working Group G. Pelletier
Request for Comments: 4996 K. Sandlund
Category: Standards Track Ericsson
L-E. Jonsson
M. West
Siemens/Roke Manor
July 2007
RObust Header Compression (ROHC): A Profile for TCP/IP (ROHC-TCP)
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 specifies a ROHC (Robust Header Compression) 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 SACK (Selective Acknowledgments)
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.
Pelletier, et al. Standards Track [Page 1]
RFC 4996 ROHC-TCP July 2007
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Existing TCP/IP Header Compression Schemes . . . . . . . . 5
3.2. Classification of TCP/IP Header Fields . . . . . . . . . . 6
4. Overview of the TCP/IP Profile (Informative) . . . . . . . . . 8
4.1. General Concepts . . . . . . . . . . . . . . . . . . . . . 8
4.2. Compressor and Decompressor Interactions . . . . . . . . . 8
4.2.1. Compressor Operation . . . . . . . . . . . . . . . . . 8
4.2.2. Decompressor Feedback . . . . . . . . . . . . . . . . 9
4.3. Packet Formats and Encoding Methods . . . . . . . . . . . 9
4.3.1. Compressing TCP Options . . . . . . . . . . . . . . . 10
4.3.2. Compressing Extension Headers . . . . . . . . . . . . 10
4.4. Expected Compression Ratios with ROHC-TCP . . . . . . . . 10
5. Compressor and Decompressor Logic (Normative) . . . . . . . . 11
5.1. Context Initialization . . . . . . . . . . . . . . . . . . 11
5.2. Compressor Operation . . . . . . . . . . . . . . . . . . . 11
5.2.1. Compression Logic . . . . . . . . . . . . . . . . . . 11
5.2.2. Feedback Logic . . . . . . . . . . . . . . . . . . . . 13
5.2.3. Context Replication . . . . . . . . . . . . . . . . . 14
5.3. Decompressor Operation . . . . . . . . . . . . . . . . . . 14
5.3.1. Decompressor States and Logic . . . . . . . . . . . . 14
5.3.2. Feedback Logic . . . . . . . . . . . . . . . . . . . . 18
5.3.3. Context Replication . . . . . . . . . . . . . . . . . 18
6. Encodings in ROHC-TCP (Normative) . . . . . . . . . . . . . . 18
6.1. Control Fields in ROHC-TCP . . . . . . . . . . . . . . . . 18
6.1.1. Master Sequence Number (MSN) . . . . . . . . . . . . . 19
6.1.2. IP-ID Behavior . . . . . . . . . . . . . . . . . . . . 19
6.1.3. Explicit Congestion Notification (ECN) . . . . . . . . 20
6.2. Compressed Header Chains . . . . . . . . . . . . . . . . . 21
6.3. Compressing TCP Options with List Compression . . . . . . 23
6.3.1. List Compression . . . . . . . . . . . . . . . . . . . 23
6.3.2. Table-Based Item Compression . . . . . . . . . . . . . 24
6.3.3. Encoding of Compressed Lists . . . . . . . . . . . . . 25
6.3.4. Item Table Mappings . . . . . . . . . . . . . . . . . 26
6.3.5. Compressed Lists in Dynamic Chain . . . . . . . . . . 28
6.3.6. Irregular Chain Items for TCP Options . . . . . . . . 28
6.3.7. Replication of TCP Options . . . . . . . . . . . . . . 28
6.4. Profile-Specific Encoding Methods . . . . . . . . . . . . 29
6.4.1. inferred_ip_v4_header_checksum . . . . . . . . . . . . 29
6.4.2. inferred_mine_header_checksum . . . . . . . . . . . . 30
6.4.3. inferred_ip_v4_length . . . . . . . . . . . . . . . . 30
6.4.4. inferred_ip_v6_length . . . . . . . . . . . . . . . . 31
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