Subject: [Diffserv] [Fwd: Protocol Action: TCP Processing of the IP Precedence Field toProposed Standard]

From: Brian E Carpenter <[email-masked]>
Date: Thu, 01 Jun 2000 11:37:18 -0500

Diffservers need to be aware of this decision.

    Brian

-------- Original Message --------
Subject: Protocol Action: TCP Processing of the IP Precedence Field toProposed Standard
Date: Wed, 31 May 2000 08:10:54 -0400
From: The IESG <[email-masked]>
To: IETF-Announce: ;;IETF-Announce:@mail-gw.hursley.ibm.com
CC: RFC Editor <[email-masked]>,Internet Architecture Board <[email-masked]>

The IESG has approved the Internet-Draft 'TCP Processing of the IP
Precedence Field' <draft-xiao-tcp-prec-03.txt> as a Proposed Standard.
This has been reviewed in the IETF but is not the product of an IETF
Working Group. The IESG contact persons Allison Mankin and Scott
Bradner.

Technical Summary
 
  This document describes a conflict between TCP  (RFC793) and DiffServ
  (RFC2475) on the use of the three leftmost bits in the TOS octet of an IPv4
  header (RFC791).  In a network that contains DiffServ capable nodes, such
  a conflict can cause failures in establishing TCP connections or can
  cause some established TCP connections to be reset undesirably. This
  document describes a modification to TCP for resolving the conflict.

  TCP requires that the precedence (and security parameters) of a connection
  must remain unchanged during the lifetime of the connection. Therefore, for
  an established TCP connection with precedence, the receipt of a segment with
  different precedence indicates an error. The connection must be reset .

  With the advent of DiffServ, intermediate nodes may modify the
  Differentiated Services Codepoint (DSCP) of the IP header to indicate the
  desired Per-hop Behavior (PHB). The DSCP includes the three bits formerly
  known as the precedence field.  Because any modification to those three bits
  will be considered illegal by endpoints that are precedence-aware, they may
  cause failures in establishing connections, or may cause established
  connections to be reset.

  With this RFC the behavior of TCP is changed to ignore the precedence of all
  received segments

Working Group Summary

  The working group supported the publication of this document.  No issues
  were raised during IETF Last-Call.

Protocol Quality

  This document has been reviewed for the IESG by Vern Paxson and Scott
  Bradner.

_______________________________________________
diffserv mailing list
[email-masked]
http://www1.ietf.org/mailman/listinfo/diffserv
Archive: http://www-nrg.ee.lbl.gov/diff-serv-arch/