[pmtud] I-D ACTION:draft-ietf-pmtud-method-05.txt

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Path MTU Discovery Working Group of the IETF.

	Title		: Path MTU Discovery
	Author(s)	: M. Mathis, J. Heffner
	Filename	: draft-ietf-pmtud-method-05.txt
	Pages		: 31
	Date		: 2005-10-25

This document describes a robust method for Path MTU Discovery that
   relies on TCP or some other Packetization Layer to probe an Internet
   path with progressively larger packets.  This method is described as
   an extension to RFC 1191 and RFC 1981, which specify ICMP based Path
   MTU Discovery for IP versions 4 and 6, respectively.

   The general strategy of the new algorithm is to start with a small
   MTU and search upward, testing successively larger MTUs by probing
   with single packets.  If the probe is successfully delivered and
   satisfies a subsequent verification phase then the MTU is raised.  If
   the probe is lost, it is treated as an MTU limitation and not as a
   congestion signal.

   There are several options for integrating PLPMTUD with classical path
   MTU discovery.  PLPMTUD can be minimally configured to perform ICMP
   black hole recovery to increase the robustness of classical path MTU
   discovery, or ICMP processing can be completely disabled, and PLPMTUD
   can completely replace classical path MTU discovery.

   In the latter configuration, PLPMTUD exactly parallels congestion
   control.  An end-to-end transport protocol adjusts non-protocol
   properties of the data stream (window size or packet size) while
   using packet losses to deduce the appropriateness of the adjustments.
   This technique seems to be more philosophically consistent with the
   end-to-end principle than relying on ICMP messages containing
   transcribed headers of multiple protocol layers.

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