[tcpm] New Version Notification for draft-zimmermann-tcp-lcd-02

Alexander Zimmermann <alexander.zimmermann@nets.rwth-aachen.de> Wed, 26 August 2009 14:13 UTC

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From: Alexander Zimmermann <alexander.zimmermann@nets.rwth-aachen.de>
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Subject: [tcpm] New Version Notification for draft-zimmermann-tcp-lcd-02
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Hi folks,

I upload a new version of our draft to the IETF repository:

As always, comments are more than welcome.



Main change from draft-zimmermann-tcp-lcd-01

The algorithm in Section 4.2 was slightly changed. Instead of reverting
the RTO by halving it, it is recalculated with help of the "Backoff_cnt"
variable. This fixes an issue that occurred when the retransmission  
was backed off but bounded by a maximum value. The algorithm in the
previous version of the draft, would have "reverted" to half of that
maximum value, instead of using the value, before the RTO was doubled
(and then bounded).


Filename:	 draft-zimmermann-tcp-lcd
Revision:	 02
Title:		 Make TCP more Robust to Long Connectivity Disruptions
Creation_date:	 2009-08-26
WG ID:		 Independent Submission
Number_of_pages: 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 connectivity disruptions as a sign of congestion,
resulting in repeated backoffs of the retransmission timer.  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 describes how standard ICMP messages can be exploited
to disambiguate true congestion loss from non-congestion loss caused
by long 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.  The specified algorithm is a TCP
sender-only modification that effectively improves TCP performance in
presence of connectivity disruptions.

// Dipl.-Inform. Alexander Zimmermann
// Department of Computer Science, Informatik 4
// RWTH Aachen University
// Ahornstr. 55, 52056 Aachen, Germany
// phone: (49-241) 80-21422, fax: (49-241) 80-22220
// email: zimmermann@cs.rwth-aachen.de
// web: http://www.umic-mesh.net