IPv6 day and tunnels

Wed Jun 6 16:00:41 UTC 2012

A few more words on MTU. What we are after is accommodation
of MTU diversity - not any one specific size. Practical limit
is (2^32 - 1) for IPv6, but we expect smaller sizes for the
near term. Operators know how to configure MTUs appropriate
for their links. 1280 is too small, and turns the IPv6
Internet into ATM.

In order to support MTU diversity, PMTUD must be made to
work. This means working to eliminate all network blockage
of ICMPv6 PTBs, while at the same time provisioning hosts
and tunnels with mechanisms that work even if no PTBs are
delivered. For hosts, that requires RFC4821. For tunnels,
that requires fragmentation.

>From an earlier message:

> 9000B may still be acceptable.

True, but what we need is not any one fixed Internet
"cell size" but rather full support for MTU diversity.

Fred
fred.l.templin at boeing.com