Re: [tcpm] I-D Action:draft-ietf-tcpm-tcp-lcd-00.txt

[Alexander Zimmermann <alexander.zimmermann at nets.rwth-aachen.de>]

Hi Folks,

the first working group version of the connectivity disruption draft is finished. In my opinion the document is feature complete. In particular, we reorganized and heavily extended the discussion section (ambiguity problems, wrapped sequence numbers, packet duplication) and introduced an interoperability issue section (ECN, Tunnels, ICMPv6, ...).

Alex

---

Changes from draft-zimmermann-tcp-lcd-02

   o  Incorporated feedback submitted by Ilpo Jarvinen.
      <http://www.ietf.org/mail-archive/web/tcpm/current/msg04841.html>

   o  Incorporated feedback submitted by Pasi Sarolahti.
      <http://www.ietf.org/mail-archive/web/tcpm/current/msg04870.html>

   o  Incorporated feedback submitted by Joe Touch.
      <http://www.ietf.org/mail-archive/web/tcpm/current/msg04895.html>
      <http://www.ietf.org/mail-archive/web/tcpm/current/msg04900.html>

   o  Extended and reorganized the discussion (Section 5):

      *  Every discussion item got its own title, so that we have a
         better overview.

      *  Extended Retransmission Ambiguity section.  Added also some
         references to the historical retransmission ambiguity problem.

      *  Heavily extended discussion about wrapped sequence numbers (see
         Joe's comments).

      *  Described the influence of packet duplication on the algorithm
         (Thanks to Ilpo).

      *  The section "Protecting Against Misbehaving Routers" is not a
         subsection anymore.  Moreover, the section was renamed to
         "Dissolving Ambiguity Issues" and has now real content.

   o  An interoperability issues section (Section 7) was added.  In
      particular comments to ECN, ICMPv6, and to the two thresholds R1
      and R2 of [RFC1122] (Section 4.2.3.5) were added.

   o  Miscellaneous editorial changes.  In particular, the algorithm has
      a name now: TCP-LCD.


Am 18.11.2009 um 17:00 schrieb <Internet-Drafts at ietf.org>:

> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the TCP Maintenance and Minor Extensions Working Group of the IETF.
> 
> 
> 	Title           : Making TCP more Robust to Long Connectivity Disruptions (TCP-LCD)
> 	Author(s)       : A. Zimmermann, A. Hannemann
> 	Filename        : draft-ietf-tcpm-tcp-lcd-00.txt
> 	Pages           : 25
> 	Date            : 2009-11-17
> 
> Disruptions in end-to-end path connectivity, which last longer than
> one retransmission timeout cause suboptimal TCP performance.  The
> reason for the performance degradation is that TCP interprets segment
> loss induced by long connectivity disruptions as a sign of
> congestion, resulting in repeated retransmission timer backoffs.
> This leads in turn to a deferred detection of the re-establishment of
> the connection since TCP waits until the next retransmission timeout
> occurs before attempting the retransmission.
> 
> This document proposes a algorithm for making TCP more robust to long
> connectivity disruptions (TCP-LCD).  The memo describes how standard
> ICMP messages can be exploited during timeout-based loss recovery to
> disambiguate true congestion loss from non-congestion loss caused by
> connectivity disruptions.  Moreover, a revert strategy of the
> retransmission timer is specified that enables a more prompt
> detection of whether the connectivity to a previously disconnected
> peer node has been restored or not.  TCP-LCD is a TCP sender-only
> modification that effectively improves TCP performance in presence of
> connectivity disruptions.
> 
> Status of this Memo
> 
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//
// Dipl.-Inform. Alexander Zimmermann
// Department of Computer Science, Informatik 4
// RWTH Aachen University
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