Formal Notation for RObust Header Compression (ROHC-FN)
RFC 4997

Approval announcement
Draft of message to be sent after approval:

From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: Internet Architecture Board <iab@iab.org>,
    RFC Editor <rfc-editor@rfc-editor.org>, 
    rohc mailing list <rohc@ietf.org>, 
    rohc chair <rohc-chairs@tools.ietf.org>
Subject: Protocol Action: 'Formal Notation for Robust Header 
         Compression (ROHC-FN)' to Proposed Standard 

The IESG has approved the following document:

- 'Formal Notation for Robust Header Compression (ROHC-FN) '
   <draft-ietf-rohc-formal-notation-14.txt> as a Proposed Standard

This document is the product of the Robust Header Compression Working 
Group. 

The IESG contact persons are Magnus Westerlund and Lars Eggert.

A URL of this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-rohc-formal-notation-14.txt

Technical Summary

  This document defines ROHC-FN (RObust Header Compression - Formal
  Notation); a formal notation to specify field encodings for
  compressed formats when defining new profiles within the ROHC
  framework. Previous header compression profiles have been so far
  specified using a combination of English text together with ASCII
  Box notation. Unfortunately, this was sometimes unclear and
  ambiguous, revealing the limitations of defining complex structures
  and encodings for compressed formats this way. The primary
  objective of the Formal Notation is to provide a more rigorous
  means to define header formats -- compressed and uncompressed -- as
  well as the relationships between them. ROHC-FN offers a library of
  encoding methods that are often used in ROHC profiles and can
  thereby help simplifying future profile development work.

Working Group Summary

  This document has been in the workings for several years, it first
  appeared as part of of a header compression research proposal known
  as "EPIC", and became an official WG item 2002, to serve the ROHC
  TCP profile development. Its form has changed through the years,
  but it has now been rather stable for a long time and is used as
  a basis for both the ROHC TCP profile and the upcoming ROHCv2
  profiles. The document has been carefully reviewed by both the WG
  and externals, and there is WG consensus that the document should
  now be published as an RFC.

Document Quality

  The formal notation specified by this document has now been put in
  use for two ROHC profile specifications, the TCP and the ROHCv2
  profiles. The document has been both manually reviewed by several
  parties with different perspectives, and checked by automated
  tools. During WGLC, the document was reviewed by the committed WG
  reviewers Mark West, Carsten Bormann and Joe Touch, as well as by
  Sally Floyd, who provided a review at the request of the Transport
  Area Directorate.

Personnel
       
  Document Sheperd for this document is Lars-Erik Jonsson, and Magnus
  Westerlund is the Responsible Area Director.


Note to RFC Editor
 
Section 3.3, 

OLD:

      UNCOMPRESSED {
         version         [  4 ];
         header_length   [  4 ];
         tos             [  6 ];

NEW: 
      UNCOMPRESSED {
         version         [  4 ];
         header_length   [  4 ];
         dscp            [  6 ];
         ^^^^

Section 3.3, page 13:

OLD:
       tos            =:= irregular(6);

NEW: 

       dscp            =:= irregular(6);
       ^^^^

Section 4.12.1.3:

OLD:

     ipv4
     {
       UNCOMPRESSED {
         version;       // 4 bits
         hdr_length;    // 4 bits
         protocol;      // 8 bits
         tos_tc;        // 6 bits

NEW:

     ipv4
     {
       UNCOMPRESSED {
         version;       // 4 bits
         hdr_length;    // 4 bits
         protocol;      // 8 bits
         dscp;          // 6 bits
         ^^^^