PMTU-Options: Path MTU Discovery Using Options

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Last updated 2004-02-11
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document describes an experimental enhancement of Path MTU Discovery that has the potential of reducing loss, speeding up convergence, reducing load in routers which would otherwise need to generate a large amount of ICMP messages, and alleviating certain additional problems (interactions with tunnels, Black Hole Detection). The idea is to use an IP Option which queries routers for their MTU before starting a Path MTU Discovery process. The result retrieved in this is used as an upper limit for Path MTU Discovery. To this end, it is fed back to the source either at the packetization layer (recommended) or at the IP layer.


Michael Welzl (

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