Re: Smallest Transit MTU

[Tony Rall <trall () almaden ibm com>]

On Wednesday, 2004-12-29 at 13:43 EST, Joe Abley <jabley () isc org> wrote:
> However, there are a growing throng of broadband users who have PPTP or
> other encaps between them and the world,

Encapsulated traffic (vpns, etc.) is indeed what I see as the largest 
contributor to connectivity problems for large packets.

> and who are able to get along
> just fine by reducing the advertised MSS in their TCP stack.

But that only affects tcp traffic - it does nothing to help other 
protocols.  In other words, it's a fairly lame circumvention that happens 
to do the job for most usage (but assuming it solves the problem often 
results in seemingly inexplicable failures when other protocols happen to 
be used).

The better solution is to ensure that PMTUD works correctly for your 
network, and get on the case of any correspondent or provider for which it 
doesn't.

 Tony Rall