RFC1883 and ipv6 spec v2

[Brian E Carpenter]

> 2/ the diff serv work (some of which is already being tested in the 
> field) may depend of the changability of some of the packet header at
> cloud (e.g. ISP) borders

I expect that diff serv will change the traffic class byte
on the fly but is unlikely to consider the flow ID at all.

It's clear that there are two camps on the flow ID - those who
believe it should be used for label switching, in which case
it changes on the fly, and those who believe it should be an
invariant. I agree we need a resolution of this but there are
arguments both ways. Anybody want to do the pro/con analysis?

  Brian Carpenter