[e2e] Internet packet size distribution - is Cisco VPN

[Loki Jorgenson]

FYI - in our experience, 1300 bytes is one of several default values
associated with Cisco VPNs.

Loki Jorgenson
e   ljorgenson at ApparentNetworks.com
t   604 433 2333 ext 105
f   604 433 2311
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w   www.ApparentNetworks.com

Message: 3
Date: Wed, 26 Oct 2005 11:10:53 -0700
From: John Heidemann <johnh at ISI.EDU>
Subject: Re: [e2e] Internet packet size distribution
To: "Ghanwani, Anoop" <anoop.ghanwani at hp.com>
Cc: Rishi Sinha <rishisin at usc.edu>, end2end-interest at postel.org
Message-ID: <200510261810.j9QIArDR022101 at dash.isi.edu>
Content-Type: text/plain; charset=US-ASCII

On Mon, 24 Oct 2005 11:05:25 PDT, "Ghanwani, Anoop" wrote: 
> 
>> We traced the recommendations for 1300B MTU to several sources. For
>> example VPN MTU recommendations, see our web page.
>
>Could this be because of IPv6 traffic being tunneled in IPv4?
>IPv6 requires that the link layer support an MTU of at least
>1280 bytes.  Add 20 bytes for an IPv4 tunnel header and you
>get 1300 bytes.

Good point.

My assumption is that VPN'ed traffic is much, much more common than
tunneled IPv6 (particularly at USC where all wireless was VPNed until
recently), but it would be good to validate that assumption.

   -John