nanog mailing list archives

Re: IP Fragmentation - Not reliable over the Internet?


From: Blake Dunlap <ikiris () gmail com>
Date: Tue, 27 Aug 2013 10:00:36 -0500

And then you have other issues like networks that arbitrarily set DF on all
packets passing through them. That burnt a good three days of my life back
in the day.

-Blake


On Tue, Aug 27, 2013 at 9:33 AM, <Valdis.Kletnieks () vt edu> wrote:

On Tue, 27 Aug 2013 00:34:57 -0700, Owen DeLong said:
That's a lot of questions he didn't ask.

This isn't your first rodeo.  You should know by now that the question
actually asked, the question *meant* to be asked, and the question that
actually needed answering are often 3 different things.

If I send a packet out as a legitimate series of fragments, what is the
chance
that they will get dropped somewhere in the middle of the path between
the
emitting host and the receiving host?

To my thinking, the answer to that question is basically "pretty close
to 0 and
if that changes in the core, very bad things will happen."

Saku Ytti and Emile Aben have numbers that say otherwise.  And there must
be a significantly bigger percentage of failures than "pretty close to 0",
or Path MTU Discovery wouldn't have a reputation of being next to useless.



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