draft-templin-tunnelmtu-01.txt

[Iljitsch van Beijnum <iljitsch@muada.com>]

On 25 okt 2003, at 2:51, Fred Templin wrote:

> General comment - it would be nice if folks would reveiw and comment
> on my drafts:
>  http://www.ietf.org/internet-drafts/draft-templin-ndiscmtu-00.txt
>  http://www.ietf.org/internet-drafts/draft-templin-tunnelmtu-01.txt
Ok, the second one first:

As far as I can tell, not being someone who builds routers, some of the 
mechanisms outlined here are problematic. For instance, determining 
whether the IP packet that carries a tunneled packet was fragmented 
means transferring information from one place in the architecture 
(reception and reassembly of IP packets) to another (handling protocol 
41). Another: doing a router sollicitation triggered by wanting to 
transmit a packet of a certain size is not a good thing.

But why bother in the first place?

Presonally, I would happily let my tunnel packets be fragmented as this 
way I don't incur a reduced MTU when using a tunnel. Sure, this costs 
extra CPU time for the tunnel endpoints but in most cases this isn't a 
problem. And when it is, the tunnel endpoints should be able to do 
PMTUD over the tunnel. And if that doesn't work, it's always possible 
to configure a smaller MTU. Don't forget that tunnels are typically 
pretty static so once everything is set up, there shouldn't be too many 
surprises.

I think this draft is solving a non-problem.


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