[pmtud] I-D ACTION:draft-ietf-pmtud-method-07.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		: Packetization Layer Path MTU Discovery
	Author(s)	: M. Mathis, J. Heffner
	Filename	: draft-ietf-pmtud-method-07.txt
	Pages		: 33
	Date		: 2006-6-12

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 a probe is successfully delivered then the
MTU can be raised.  If the probe is lost, it is treated as an MTU
limitation and not as a congestion signal.

PLPMTUD introduces some flexibility in the implementation of
classical Path MTU discovery.  If can be configured to perform just
ICMP black hole recovery to increase the robustness of classical Path
MTU Discovery, or at the other extreme, all ICMP processing can be
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 properties of the
data stream (window size or packet size) while using packet losses to
deduce the appropriateness of the adjustments.  This technique is
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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