[170601] in North American Network Operators' Group
Re: real-world data about fragmentation
daemon@ATHENA.MIT.EDU (bmanning@vacation.karoshi.com)
Wed Apr 2 14:51:49 2014
Date: Wed, 2 Apr 2014 11:50:53 -0700
From: bmanning@vacation.karoshi.com
To: Joe Abley <jabley@hopcount.ca>
In-Reply-To: <253521C4-EA53-4CF3-BC5F-EBC424989DFC@hopcount.ca>
Cc: NANOG Mailing List <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
I can send you a copy of an invited presentation at AINTEC from 2009.
/bill
On Wed, Apr 02, 2014 at 02:14:22PM -0400, Joe Abley wrote:
> Hi all,
>
> It's common wisdom that a datagram that needs to be fragmented between endpoints (because it is bigger than the path MTU) will demonstrate less reliable delivery and reassembly than a datagram that doesn't need to be fragmented, because math, firewall, other, take your pick.
>
> Is anybody aware of any wide-scale studies that examine the probability of fragmentation of datagrams of different sizes?
>
> 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). 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.
>
>
> Joe
