datatracker.ietf.org
Sign in
Version 5.12.0, 2015-02-26
Report a bug

RObust Header Compression (ROHC): Corrections and Clarifications to RFC 3095
RFC 4815

Document type: RFC - Proposed Standard (February 2007; No errata)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4815 (Proposed Standard)
Responsible AD: Magnus Westerlund
Send notices to: rohc-chairs@ietf.org

Network Working Group                                       L-E. Jonsson
Request for Comments: 4815                                   K. Sandlund
Updates: 3095, 3241, 3843, 4019, 4362                       G. Pelletier
Category: Standards Track                                      P. Kremer
                                                           February 2007

                   RObust Header Compression (ROHC):
               Corrections and Clarifications to RFC 3095

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

   RFC 3095 defines the RObust Header Compression (ROHC) framework and
   profiles for IP (Internet Protocol), UDP (User Datagram Protocol),
   RTP (Real-Time Transport Protocol), and ESP (Encapsulating Security
   Payload).  Some parts of the specification are unclear or contain
   errors that may lead to misinterpretations that may impair
   interoperability between different implementations.  This document
   provides corrections, additions, and clarifications to RFC 3095; this
   document thus updates RFC 3095.  In addition, other clarifications
   related to RFC 3241 (ROHC over PPP), RFC 3843 (ROHC IP profile) and
   RFC 4109 (ROHC UDP-Lite profiles) are also provided.

Jonsson, et al.             Standards Track                     [Page 1]
RFC 4815       Corrections and Clarifications to RFC 3095  February 2007

Table of Contents

   1. Introduction and Terminology ....................................3
   2. CRC Calculation and Coverage ....................................4
      2.1. CRC Calculation ............................................4
      2.2. Padding Octet and CRC Calculations .........................4
      2.3. CRC Coverage in CRC Feedback Options .......................5
      2.4. CRC Coverage of the ESP NULL Header ........................5
   3. Mode Transition .................................................5
      3.1. Feedback During Mode Transition to U- and O-Mode ...........5
           3.1.1. Mode Transition Procedures Allowing Sparse Feedback .6
           3.1.2. Transition from Reliable to Optimistic Mode .........7
           3.1.3. Transition to Unidirectional Mode ...................8
      3.2. Feedback During Mode Transition ............................8
      3.3. Packet Decoding During Mode Transition .....................9
   4. Timestamp Encoding ..............................................9
      4.1. Encoding Used for Compressed TS Bits .......................9
      4.2. (De)compression of TS without Transmitted TS Bits .........10
      4.3. Interpretation Intervals for TS Encoding ..................11
      4.4. Scaled RTP Timestamp Encoding .............................11
           4.4.1. TS_STRIDE for Scaled Timestamp Encoding ............11
           4.4.2. TS Wraparound with Scaled Timestamp Encoding .......12
           4.4.3. Algorithm for Scaled Timestamp Encoding ............12
      4.5. Recalculating TS_OFFSET ...................................14
      4.6. TS_STRIDE and the Tsc Flag in Extension 3 .................14
      4.7. Using Timer-Based Compression .............................15
   5. List Compression ...............................................15
      5.1. CSRC List Items in RTP Dynamic Chain ......................15
      5.2. Multiple Occurrences of the CC Field ......................15
      5.3. Bit Masks in List Compression .............................16
      5.4. Headers Compressed with List Compression ..................16
      5.5. ESP NULL Header List Compression ..........................17
      5.6. Translation Tables and Indexes for IP Extension Headers ...17
      5.7. Reference List ............................................17
      5.8. Compression of AH and GRE Sequence Numbers ................18
   6. Updating Properties ............................................19
      6.1. Implicit Updates ..........................................19
      6.2. Updating Properties of UO-1* ..............................20
      6.3. Context Updating Properties for IR Packets ................20
      6.4. RTP Padding Field (R-P) in Extension 3 ....................20
      6.5. RTP eXtension bit (X) in dynamic part .....................21
   7. Context management and CID/context Reuse .......................21
      7.1. Persistence of Decompressor Contexts ......................21
      7.2. CID/Context Reuse .........................................21

[include full document text]