Subject: RE: (ngtrans) Re: I-D ACTION:draft-ietf-ngtrans-mech-v2-00.txt

From: "Christian Huitema" <[email-masked]>
Date: Sun, 18 Aug 2002 22:35:24 -0700

> >As I said before, I think the same motivation and tradeoffs for PMTU
> discovery
> >apply for traffic whether or not it is encapsulated in multiple IP
> >headers or only contains one IP header.
> 
> 	i understand your goal (to make use of bigger link MTU as much
as
> 	possible), but i don't think the benefit outweigh the above
> problems.

I think Itojun is right on this one: tunneling is pretty much a band
aid, and you want to keep it simple. In fact, I would make a distinction
between tunneling as a substitute for a link in the middle of the
network and end-to-end encapsulation. If you work end-to-end, then you
can do a reasonable job of PMTU discovery, even if you add a layer of
encapsulation. OTOH, if you are using the tunnel as a link, you pretty
much have to assume a fixed MTU for the link; in the absence of special
knowledge and configuration, the simplest is to assume the minimal MTU,
1280 bytes.