Dan,Thanks for the RFC4821 and M Petit-Huguenin's I-D references. I knew and their predecessors but had not read these two.
The value of PMTUD mechanisms that work even when ICMP error messages are missing is clear.
Yet, since convergence to the right PMTU can be much faster if ICMP error messages are forwarded and processed, it seems useful to have this fact well understood, and advertised.
NAT and FW providers have IMO to keep (or restore) their motivation to forward ICMP error messages on established connections.
Rémi Després Dan Wing - Le 8/18/08 8:58 AM :
I don't recall if RFC4821 was included in your earlier list. RFC4821describes how to do Path MTU Discovery without ICMP.As you know, doing PMTUD over UDP requires each application to do it themselves. Marc Petit-Huguenin describes how to do RFC4821-style (that is, ICMP-less) PMTUD for UDP in draft-petithuguenin-behave-stun-pmtud-01, provided the application can demultiplex STUN messages from its normal application payloads (the STUN magic-cookie and the STUN fingerprint can be used to demux, which makes demuxing easier). -d