North American Network Operators Group

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Re: MTU of the Internet?

  • From: Marc Slemko
  • Date: Wed Feb 04 16:18:32 1998

On Wed, 4 Feb 1998, Eric Germann wrote:

> With all the paranoids trying to block all ICMP, not just ICMP_ECHO, doesn't
> that essentially break PMTUD.  576 may not be efficient, but its probably
> the safest to assume.

No, it just means that these paranoids should get a clue.  Even servers
coloed at large NSPs sometimes have suck bogus filters applied by the NSP
that should know better.

On a side note, from what I understand Win95 implements blackhole
detection for this situation (don't know of many Unixes that do that...),
although it isn't enabled by default and you probably need patch mumble
and mumble to get it.  Not sure if it works or not.