TCP/IP Field Behavior
RFC 4413

 
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Type RFC - Informational (March 2006; Errata)
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Network Working Group                                            M. West
Request for Comments: 4413                                     S. McCann
Category: Informational                      Siemens/Roke Manor Research
                                                              March 2006

                         TCP/IP Field Behavior

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This memo describes TCP/IP field behavior in the context of header
   compression.  Header compression is possible because most header
   fields do not vary randomly from packet to packet.  Many of the
   fields exhibit static behavior or change in a more or less
   predictable way.  When a header compression scheme is designed, it is
   of fundamental importance to understand the behavior of the fields in
   detail.  An example of this analysis can be seen in RFC 3095.  This
   memo performs a similar role for the compression of TCP/IP headers.

West & McCann                Informational                      [Page 1]
RFC 4413                 TCP/IP Field Behavior                March 2006

Table of Contents

   1. Introduction ....................................................3
   2. General classification ..........................................4
      2.1. IP Header Fields ...........................................5
         2.1.1. IPv6 Header Fields ....................................5
         2.1.2. IPv4 Header Fields ....................................7
      2.2. TCP Header Fields .........................................10
      2.3. Summary for IP/TCP ........................................11
   3. Classification of Replicable Header Fields .....................11
      3.1. IPv4 Header (Inner and/or Outer) ..........................12
      3.2. IPv6 Header (inner and/or outer) ..........................14
      3.3. TCP Header ................................................14
      3.4. TCP Options ...............................................15
      3.5. Summary of Replication ....................................16
   4. Analysis of Change Patterns of Header Fields ...................16
      4.1. IP Header .................................................19
         4.1.1. IP Traffic-Class / Type-Of-Service (TOS) .............19
         4.1.2. ECN Flags ............................................19
         4.1.3. IP Identification ....................................20
         4.1.4. Don't Fragment (DF) flag .............................22
         4.1.5. IP Hop-Limit / Time-To-Live (TTL) ....................22
      4.2. TCP Header ................................................23
         4.2.1. Sequence Number ......................................23
         4.2.2. Acknowledgement Number ...............................24
         4.2.3. Reserved .............................................25
         4.2.4. Flags ................................................25
         4.2.5. Checksum .............................................26
         4.2.6. Window ...............................................26
         4.2.7. Urgent Pointer .......................................27
      4.3. Options ...................................................27
         4.3.1. Options Overview .....................................28
         4.3.2. Option Field Behavior ................................29
   5. Other Observations .............................................36
      5.1. Implicit Acknowledgements .................................36
      5.2. Shared Data ...............................................36
      5.3. TCP Header Overhead .......................................37
      5.4. Field Independence and Packet Behavior ....................37
      5.5. Short-Lived Flows .........................................37
      5.6. Master Sequence Number ....................................38
      5.7. Size Constraint for TCP Options ...........................38
   6. Security Considerations ........................................39
   7. Acknowledgements ...............................................39
   8. References .....................................................40
      8.1. Normative References ......................................40
      8.2. Informative References ....................................41

West & McCann                Informational                      [Page 2]
RFC 4413                 TCP/IP Field Behavior                March 2006

1.  Introduction

   This document describes the format of the TCP/IP header and the
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