[165253] in North American Network Operators' Group
Re: IP Fragmentation - Not reliable over the Internet?
daemon@ATHENA.MIT.EDU (Owen DeLong)
Tue Aug 27 14:53:17 2013
From: Owen DeLong <owen@delong.com>
In-Reply-To: <105365.1377614001@turing-police.cc.vt.edu>
Date: Tue, 27 Aug 2013 11:47:15 -0700
To: Valdis.Kletnieks@vt.edu
Cc: North American Network Operators' Group <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Aug 27, 2013, at 07:33 , 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.
>=20
> 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.
>=20
>> 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?
>=20
>> 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."
>=20
> 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.
No, their numbers describe what happens to single packets of differing =
sizes.
Nothing they did describes results of actually fragmented packets.
Owen
