[170754] in North American Network Operators' Group
Re: real-world data about fragmentation
daemon@ATHENA.MIT.EDU (Fernando Gont)
Tue Apr 8 06:29:05 2014
Date: Tue, 08 Apr 2014 07:28:25 -0300
From: Fernando Gont <fernando@gont.com.ar>
To: Joe Abley <jabley@hopcount.ca>, NANOG Mailing List <nanog@nanog.org>
In-Reply-To: <253521C4-EA53-4CF3-BC5F-EBC424989DFC@hopcount.ca>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Hi, Joe,
On 04/02/2014 03:14 PM, Joe Abley wrote:
> Is anybody aware of any wide-scale studies that examine the
> probability of fragmentation of datagrams of different sizes?
We're in the process of measuring some (kind of related stuff). If
you're interested in this data, we might be able to provide something
along these lines in 1 month or so...
It seems to be mostly about measuring the MTU to as many destinations as
possible, so to speak...
> For example, I could reasonable expect an IPv4 packet of 576 bytes
> not to be fragmented very often (to choose a size not at random).
Note: there shouldn't be any special magic around this number (usualy
mistakenly interpreted as the minimum IPv6 MTU, but rather being the
minimum IPv4 reassembly buffer size).
> The
> probability of a 10,000 octet IPv4 packet getting fragmented seems
> likely to be 100%, if we're talking about arbitrary paths across the
> Internet.
>
> What does the curve look like between 576 bytes and 10,000 bytes?
>
> I might expect exciting curve action around 1500 bytes (because
> ethernet), 1492 (PPPoE), 1480 (GRE), etc. But I'm interested in
> actual data.
>
> Anybody have any pointers? IPv4 and IPv6 are both interesting.
Probably off-topic, but since you mentioned reliability of IPv6
fragmentation:
*
<http://www.iepg.org/2013-11-ietf88/fgont-iepg-ietf88-ipv6-frag-and-eh.pdf>
* <http://www.iepg.org/2014-03-02-ietf89/fgont-iepg-ietf89-eh-update.pdf>
Thanks!
Cheers,
--
Fernando Gont
e-mail: fernando@gont.com.ar || fgont@si6networks.com
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1
