Hi Ole, > in my understanding the 1280 minimum MTU for IPv6 was already chosen to > accommodate nested tunnels.
Right, but.. > the expectation made, I believe, was that native links support at least > an MTU of 1500 bytes, But, that expectation went out the window at the same time the IPv6 minMTU was set to 1280 - so now 1280 is all that can be expected. So, without fragmentation, when the tunnel ingress receives a 1280 packet, it emits a (1280+HLEN) packet. If that packet is dropped at a link that configures a 1280 MTU, then it simply black holes. > allowing 220 bytes for tunnel encap (5 IPv6 headers). Tunnels within tunnels presents an additional pain point, but the plain truth is that IPv6 links only need to configure a 1280 MTU; not a 1500. > you want to avoid reassembly at tunnel endpoints, if you care about > performance that is. Unfortunately, reassembly is absolutely necessary if the tunnel is configured over a path that contains at least one 1280 link (see above). Thanks - Fred fred.l.temp...@boeing.com > cheers, > Ole -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
