Hi, Fred, On 12/19/2012 02:41 PM, Templin, Fred L wrote: > I am thinking of the case of links (e.g., tunnels) in the middle > of the network that must perform link adaptation in order to meet > the 1280 byte minimum IPv6 MTU. For example, if a tunnel is > configured over a link that has an MTU less than (1280+HLEN), the > tunnel ingress will see an MTU smaller than 1280. In that case, > RFC2473 says that the tunnel ingress should perform fragmentation > on the encapsulated packet and the tunnel egress gets to do the > reassembly. But, that can amount to a lot of extra work for the > tunnel egress. > > To save the egress from this burden then, it would be great if > there were a way to get the source host to perform fragmentation > so that the destination gets to do the reassembly. In lieu of > that, it would be preferable for the tunnel ingress to perform > fragmentation on the inner packet before encapsulation provided > the inner packet includes an IPv6 fragment header.
That sounds sensible -- although I guess this would require > I talk about this in my draft on "IPv6 Path MTU Updates": > > http://www.ietf.org/id/draft-generic-6man-tunfrag-06.txt > > This document talks about taking care of packets that are in > the "red zone" size between 1280 and 1500 bytes when there > is a link in the path (e.g., a tunnel) that must perform > link adaptation to meet the minimum size. And, it seeks to > update RFC2460 by allowing the middlebox to signal the host, > and to perform fragmentation on the inner packet when the > packet includes an IPv6 fragment header. It would be good > to get your feedback on this document. I'd be glad to review it. Will do it during these seasons. Cheers, -- Fernando Gont SI6 Networks e-mail: [email protected] PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492 -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
