North American Network Operators Group

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Re: MTU of the Internet?

  • From: Marc Slemko
  • Date: Thu Feb 05 14:55:47 1998

On Thu, 5 Feb 1998, Phil Howard wrote:

> IMHO setting DF should not be allowed where the MTU is greater than 576,
> or whatever number today constitutes the "minimum reasonable requirement"
> which I would say isn't larger than 1006.  Maybe in a few years we can
> kiss SLIP bye-bye and make sure everything is 1500.

Erm... no.  The whole point of setting the DF bit is to avoid
fragmentation.  Read up on path MTU discovery to see why it is a good
thing.  Just because braindead filters cause problems is no reason to
suggest that PMTU discovery is bad.  It becomes even more critical in IPv6
where routers don't fragment period, so people had better get used to it.

Trying to force everyone to have the same MTU simply is not practical. 
You will always have systems with higher path MTUs that can get a gain
from knowing it and you will always have systems with lower MTUs for
whatever reason.

> Netscape's web server is broken.  And in more ways than just the DF thing.

It has nothing to do with what web server you are running.