Re: routing protocols will provide path-MTU

[Steve Deering <[e-mail]>]

Thanks, Noel.  Your message confirms my suspicion that different people
are thinking of different things when they say, "Within a few years,
the routing protocols will be providing MTU information."

I think a lot of people have the idea that Craig and Jeff mentioned,
that current-generation routing protocols will be enhanced to slosh
MTU information around, along with the other metrics that they
currently exchange.  I wanted to kill that notion, because of its
scaling problems.

Then there is the grand vision that you outlined.  I'd put that in the
same category as, "In a few years, everything will be carried in ATM
cells which will provide internal fragmentation and reassembly of IP
packets; therefore, we won't have to do MTU discovery."  In other words,
it is a long ways off and far from certain.  It should not discourage
us from coming up with a good MTU discovery protocol with a long
projected lifetime.

(That's not to say that we should take a long time doing it!  I do feel
some guilt for bringing up alternate proposals at this late date, but I
don't think I'm taking us "around in circles".  Rather, I believe I am
exploring a part of the solution space that we haven't examined thoroughly
before.  Think of it as "spiralling-in".)

Steve