[170630] in North American Network Operators' Group
Re: real-world data about fragmentation
daemon@ATHENA.MIT.EDU (Jennifer Rexford)
Wed Apr 2 16:30:55 2014
From: Jennifer Rexford <jrex@CS.Princeton.EDU>
In-Reply-To: <20140402185053.GB23819@vacation.karoshi.com>
Date: Wed, 2 Apr 2014 15:30:11 -0400
To: bmanning@vacation.karoshi.com
Cc: NANOG Mailing List <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
This isn't a direct answer to the question, but I find this paper pretty =
useful (even though it is dated now):
Beyond Folklore: Observations on Fragmented Traffic
by Colleen Shannon, David Moore, and k claffy
IEEE/ACM Transactions on Networking, December 2002
http://www.caida.org/publications/papers/2002/Frag/frag.pdf
(Bill, I'd be curious to see your AINTEC slides, too.)
-- Jen
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On Apr 2, 2014, at 2:50 PM, bmanning@vacation.karoshi.com wrote:
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> I can send you a copy of an invited presentation at AINTEC from 2009.
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> /bill
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> On Wed, Apr 02, 2014 at 02:14:22PM -0400, Joe Abley wrote:
>> Hi all,
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>> 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.
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>> Is anybody aware of any wide-scale studies that examine the =
probability of fragmentation of datagrams of different sizes?
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>> 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.
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>> What does the curve look like between 576 bytes and 10,000 bytes?
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>> I might expect exciting curve action around 1500 bytes (because =
ethernet), 1492 (PPPoE), 1480 (GRE), etc. But I'm interested in actual =
data.
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>> Anybody have any pointers? IPv4 and IPv6 are both interesting.
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>> Joe
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