Re: Thoughts on increasing MTUs on the internet

["David W. Hankins" <David_Hankins () isc org>]

Hopefully I'll be forgiven for geeking out over DHCP on nanog-l twice
in the same week.

On Thu, Apr 12, 2007 at 11:20:18AM +0200, Iljitsch van Beijnum wrote:
> 1. It's no longer necessary to limit the subnet MTU to that of the  
> least capable system

I dunno for that.

> 2. It's no longer necessary to manage 1500 byte+ MTUs manually

But for this, there has been (for a long time now) a DHCPv4 option
to give a client its MTU for the interface being configured (#26,
RFC2132).

The thing is, not very many (if any) clients actually request it.
Possibly because of problem #1 (if you change your MTU, and no one
else does, you're hosed).

So, if you solve for the first problem in isolation, you can
easily just use DHCP to solve the second with virtually no work
and probably "only" (heh) client software updates.


I could also note that your first problem plagues DHCP software
today...it's further complicated...let's just say it sucks, and
bad.

If one were to solve that problem for DHCP speakers, you could
probably put a siphon somewhere in the process.

But it's an even harder problem to solve.

-- 
David W. Hankins        "If you don't do it right the first time,
Software Engineer               you'll just have to do it again."
Internet Systems Consortium, Inc.       -- Jack T. Hankins

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