Subject: [tcpm] Revising RFC2581: draft-ietf-tcpm-rfc2581bis-00.txt

From: Ethan Blanton <[email-masked]>
Date: Mon, 23 Jan 2006 22:23:09 -0500

Hi all,

Mark Allman, Vern Paxson and I are ready to push a revised version of
RFC2581 to the archives, draft-ietf-tcpm-rfc2581bis-00.txt .  This is
a charter goal for this working group, so we would love to have some
feedback on the issue.  Until this hits the archives:

http://www.icir.org/mallman/papers/draft-ietf-tcpm-rfc2581bis-00.txt

Note that the changes in this revision are specifically designed to be
well-understood and non-contentious, as the goal is to move this
document to Draft Standard.  (A summary of changes follows.)  In
general, standards track RFC changes since RFC2581 have been
integrated from elsewhere with very few other changes.  There are a
few clarifications (such as the definition of duplicate acknowledgment
recently discussed on this list), as well.

Please peruse this document when you get a chance (particularly if you
know of a particular clarity issue or outdated text in RFC2581; make
sure we took care of it!) and provide feedback to us.  On-list
feedback is most welcome, to stir community discussion.

7.  Changes Relative to RFC 2581

    A specific definition for "duplicate acknowledgment" has been
    added, based on the definition used by BSD TCP.

    The initial window requirements were changed to allow Larger
    Initial Windows as standardized in [RFC3390].  Additionally, the
    steps to take when an initial window is discovered to be too large
    due to Path MTU Discovery [RFC1191] are detailed.

    The recommended initial value for ssthresh has been changed to say
    that it SHOULD be arbitrarily high, where it was previously MAY.
    This is to provide additional guidance to implementors on the
    matter.

    During slow start, the usage of Appropriate Byte Counting [RFC3465]
    with L=1*SMSS is explicitly recommended.  The method of increasing
    cwnd given in [RFC2581] is still explicitly allowed.  Byte counting
    during congestion avoidance is also recommended, while the method
    from [RFC2581] and other safe methods are still allowed.

    The treatment of ssthresh on retransmission timeout was clarified.
    Specifically, Equation (3) from [RFC2581] was split into Equations
    (4) and (5) in this document.

    The description of fast retransmit and fast recovery has been
    clarified, and the use of Limited Transmit [RFC3042] is now
    recommended.

    The restart window has been changed to min(IW,cwnd) from IW.  This
    behavior was described as "experimental" in [RFC2581].

    It is now recommended that TCP implementors implement an advanced
    loss recovery algorithm conforming to the principles outlined in
    this document.

    The security considerations have been updated to discuss ACK
    division and recommend byte counting as a counter to this attack.

Ethan
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