Fred, >> Yes, but sending at 1280 does not work for IP tunnels. The whole purpose of the minimum MTU was to give space for tunnel headers >> (1500-1280). > > But, if non-tunnel links set a 1280 MTU which is perfectly OK with the standard then > there is no space for headers. Given the issues with classical PMTUD then (plus the > non-applicability of RFC4821 for tunnels) the only solution for tunnels is fragmentation. > I'll let Joe step in if he wants to. You are correct. "Does not work for IP tunnels without fragmenting the outer header" is what I should have written. Of course it appears IPv6 fragments have a order of magnitude higher drop probability than ICMP PMTUD messages. Pick your poison. Best regards, Ole
Attachment:
signature.asc
Description: Message signed with OpenPGP