IP Header Compression
RFC 2507

Document Type RFC - Proposed Standard (February 1999; No errata)
Last updated 2013-03-02
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Network Working Group                                       M. Degermark
Request for Comments: 2507           Lulea University of Technology/SICS
Category: Standards Track                                    B. Nordgren
                        Lulea University of Technology/Telia Research AB
                                                                 S. Pink
                                     Lulea University of Technology/SICS
                                                           February 1999

                         IP Header Compression

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 (1999).  All Rights Reserved.

Abstract

   This document describes how to compress multiple IP headers and TCP
   and UDP headers per hop over point to point links. The methods can be
   applied to of IPv6 base and extension headers, IPv4 headers, TCP and
   UDP headers, and encapsulated IPv6 and IPv4 headers.

   Headers of typical UDP or TCP packets can be compressed down to 4-7
   octets including the 2 octet UDP or TCP checksum. This largely
   removes the negative impact of large IP headers and allows efficient
   use of bandwidth on low and medium speed links.

   The compression algorithms are specifically designed to work well
   over links with nontrivial packet-loss rates. Several wireless and
   modem technologies result in such links.

TABLE OF CONTENTS

   1.  Introduction..............................................3
   2.  Terminology...............................................5
   3.  Compression method........................................7
        3.1.  Packet types.......................................8
        3.2.  Lost packets in TCP packet streams.................9
        3.3.  Lost packets in UDP and non-TCP packet streams....10
   4.  Grouping packets into packet streams.....................14

Degermark, et. al.          Standards Track                     [Page 1]
RFC 2507                 IP Header Compression             February 1999

        4.1.  Guidelines for grouping packets...................15
   5.  Size Issues..............................................16
        5.1.  Context identifiers...............................16
        5.2.  Size of the context...............................17
        5.3.  Size of full headers..............................18
           5.3.1.  Length fields in full TCP headers............19
           5.3.2.  Length fields in full non-TCP headers........19
   6.  Compressed Header Formats................................20
   7.  Compression of subheaders................................22
        7.1.  IPv6 Header.......................................24
        7.2.  IPv6 Extension Headers............................25
        7.3.  Options...........................................25
        7.4.  Hop-by-hop Options Header.........................26
        7.5.  Routing Header....................................26
        7.6.  Fragment Header...................................27
        7.7.  Destination Options Header........................28
        7.8.  No Next Header....................................29
        7.9.  Authentication Header.............................29
        7.10. Encapsulating Security Payload Header.............29
        7.11. UDP Header........................................30
        7.12. TCP Header........................................30
        7.13. IPv4 Header.......................................33
        7.14  Minimal Encapsulation header......................34
   8.  Changing context identifiers.............................35
   9.  Rules for dropping or temporarily storing packets........35
   10. Low-loss header compression for TCP .....................36
        10.1.  The "twice" algorithm............................37
        10.2.  Header Requests..................................37
   11. Links that reorder packets...............................38
        11.1.  Reordering in non-TCP packet streams.............39
        11.2.  Reordering in TCP packet streams.................39
   12. Hooks for additional header compression..................40
   13. Demultiplexing...........................................41
   14. Configuration Parameters.................................42
   15. Implementation Status....................................43
   16. Acknowledgments..........................................44
   17. Security Considerations..................................44
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