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RObust Header Compression (ROHC): A Profile for TCP/IP (ROHC-TCP)
RFC 6846

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 2013

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Pelletier, et al.            Standards Track                    [Page 2]
RFC 6846                        ROHC-TCP                    January 2013

Table 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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