Improving the Robustness of TCP to Non-Congestion Events
RFC 4653

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>, 
    tcpm mailing list <tcpm@ietf.org>, 
    tcpm chair <tcpm-chairs@tools.ietf.org>
Subject: Document Action: 'Improving the Robustness of TCP to 
         Non-Congestion Events' to Experimental RFC 

The IESG has approved the following document:

- 'Improving the Robustness of TCP to Non-Congestion Events '
   <draft-ietf-tcpm-tcp-dcr-08.txt> as an Experimental RFC

This document is the product of the TCP Maintenance and Minor Extensions 
Working Group. 

The IESG contact persons are Lars Eggert and Magnus Westerlund.

A URL of this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-tcpm-tcp-dcr-08.txt

Technical Summary
 
   This document specifies Non-Congestion Robustness (NCR) for TCP. 
   One of the ways TCP detects loss is using the arrival of three duplicate
   acknowledgments. However, this heuristic is not always correct, notably
   in the case when network paths reorder segments.  TCP-NCR is designed
   to mitigate this degraded performance by increasing the number of
   duplicate acknowledgments required to trigger loss recovery, based on
   the current state of the connection, in an effort to better disambiguate
   true segment loss from segment reordering.
 
Working Group Summary
 
   This draft has attracted considerable interest in the WG, with many
   different people commenting on reviewing various iterations. The
   consensus was that although the specific benefits of the NCR
   extensions remain to be investigated, the mechanism itself is
   suitably ready for publication as an Experimental RFC.
 
Protocol Quality
 
   PROTO Shepherd: Ted Faber (faber@isi.edu)

   The Gen-ART reviewer (Eric Gray, eric.gray@marconi.com) has found this
   ready for publication as an Experimental RFC.

   Chris Lonvick (clonvick@cisco.com) has reviewed this draft for the
   Security Directorate.

   Lars Eggert has reviewed this spec for the IESG.

Note to RFC Editor

Section 7, the only paragraph

OLD:
    We do not believe there are security implications involved with TCP-
    NCR over and above those for general TCP congestion control
    [RFC2581].  In particular, the Extended Limited Transmit algorithms
    specified in this document have been specifically designed not to be
    susceptible to the sorts of ACK splitting attacks TCP's general TCP
    congestion control is vulnerable to (as discussed in [RFC3465]).

NEW:
    General attacks against the congestion control of TCP are described
    in [RFC2581].  SACK-based loss recovery for TCP [RFC3517] mitigates
    some of the duplicate ACK attacks against TCP's congestion control.
    This document builds upon that work, and the Extended Limited
    Transmit algorithms specified in this document have been designed to
    thwart the ACK division problems that are described in [RFC3465].

(I.e., just replace the entire paragraph.)