On Sun, 9 May 2004, Masataka Ohta wrote: > Back to the original problem, PMTUD depends on the capabilities > of intermediate systems on a path to generate certain ICMP, > generation of which is as complex as fragmentation itself, > that it is not very end to end. > > That is, PMTUD is a broken concept. This is the whole point of reopening the original pmtud working group. http://www.ietf.org/html.charters/pmtud-charter.html See draft-ietf-pmtud-method-01.txt I quote: This document describes a robust new method for Path MTU Discovery that relies on TCP or 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. ... The general strategy of the new algorithm is to start with a small MTU and probe upward, testing successively larger MTUs by probing with single packets. If the probe is successfully delivered, then the MTU is raised. If the probe is lost, it is treated as an MTU limitation and not as a congestion signal. This does not require any messages from the network, and works just fine with arbitrary middleboxes that either toss over-sized frames or ICMP messages. Comments, suggestions and additions to the text are welcome. The document is not well baked, but there is running code. There is some (slightly out of date) background info at http://www.psc.edu/~mathis/MTU/#pmtud Thanks, --MM-- ------------------------------------------- Matt Mathis http://www.psc.edu/~mathis Work:412.268.3319 Home/Cell:412.654.7529 ------------------------------------------- _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf