> -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Rémi Després > Sent: Tuesday, February 09, 2010 1:59 AM > To: Templin, Fred L > Cc: [email protected]; Behave WG > Subject: Re: [Softwires] [BEHAVE] PMTU Discovery and ICMPv6 filtering > > > Le 8 févr. 2010 à 22:08, Templin, Fred L a écrit : > > > Also, there seems to be some evidence that ICMPv6 PTB > > messages are being dropped in the network. > > In IPv6, I hope it will be possible to agree at least that > PTB messages SHOULD be forwarded (if not MUST). > Reasons to not agree should IMHO be seriously documented.
Ben Stasiewicz's tests [*] on the IPv6 Internet show that 56% of IPv6 hosts do not properly respond to ICMPv6 packet-too-big with an MTU<1280. I do not believe additional MUSTs in RFCs from the IETF would have a noticeable effect. [*] http://www.ietf.org/mail-archive/web/behave/current/msg08093.html -d > > ... for DF=1 packets the tunnel > > ingress MUST send an ICMP PTB when the packet is larger > > than a fixed minimum tunnel MTU and also too large to > > traverse the tunnel in a single piece. For packets that > > are no larger than the fixed minimum tunnel MTU, the > > tunnel ingress SHOULD use tunnel fragmentation (i.e., > > SEAL segmentation and reassembly). Presumably, the tunnel > > ingress would choose a fixed minimum tunnel MTU that is > > large enough so that source hosts will not see excessive > > data loss and retransmissions due to path MTU discovery > > interactions. > > > > For many/most deployments, a fixed minimum tunnel MTU of > > 1500 bytes would seem advisable. > > In my understanding, we can keep the current IPv6 value of > 1280 as the minimum that has to traverse ALL tunnels, and > note that if a tunnel has an internal mechanism to fragment > at entrance and reassemble at exit (e.g. SEAL), the tunnel > advertised MTU can become independent from that of the > traversed infrastructure. > > Thoughts? > > Cheers, > RD > _______________________________________________ > Softwires mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/softwires _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
