RE: The IPv4 Internet MTU

[Rémi Denis-Courmont <rdenis@simphalempin.com>]

On Thu, 27 Sep 2007 16:36:09 -0700, Christian Huitema

<huitema@windows.microsoft.com> wrote:

>> Why not just set the Teredo interface MTU to (64KB-ENCAPS)?

>> Then, take special care to make sure the small packets get

>> through but let the big packets take care of themselves.



> The problem is UDP fragmentation. By nature, it is unreliable: the more

> fragments, the more chances to lose one of them, thus causing the loss of

> the entire packet. This is aggravated by NAT behavior: some NAT will try

to

> reassemble the packets, but others will just pass the 1st fragment and

drop

> the next ones.



Maybe Fred was hinting that Teredo could have defined its

fragmentation layer between UDP and IPv6. But while this would

work-around on-path fragmentation it would bring a naughty congestion

control issue - one simply cannot send 40 datagrams of 1500 bytes each

with no pacing. And we don't want to have to do congestion control,

right?



-- 

Rémi Denis-Courmont

http://www.remlab.net/