[e2e] Internet packet size distribution

Joe Touch touch at ISI.EDU
Wed Oct 26 13:14:41 PDT 2005


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John Heidemann wrote:
> 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

It can be difficult to find such traffic, since it isn't always on
protocol 50 (ESP) or 4 (IP-IP tunnel); the totals for those are under
1%, as per CAIDA's traces from around 2002.

The rest shows up hidden inside UDP or even TCP, esp. to traverse
firewalls or NA(P)Ts, and cannot as easily be measured.

Joe
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