Subject: RE: PMTU blackhole detection

From: "Timothy E. Enos" <[email-masked]>
Date: Fri, 22 Apr 2011 14:44:44 -0400

I concur with Fred that IPv6 links over the network should have an MTU >1280 if possible. 

The fragmentation that could occur at say the head-end of a tunnel seems enough of a contraindication in general for it having a 1280 MTU.

Efficient use of (up)links is clearly another consideration when setting MTU (and MSS for that matter).

Tim Enos
Ps 127:3-5

-----Original Message-----
From: Templin, Fred L <[email-masked]>
Sent: Friday, April 22, 2011 1:17 PM
To: Bob Hinden <[email-masked]>; Dan Wing <[email-masked]>
Cc: [email-masked] <[email-masked]>; 'Brian E Carpenter' <[email-masked]>
Subject: RE: PMTU blackhole detection

IMHO, IPv6 links that occur in the network (even tunnels)
should try to do better than 1280 if possible. Otherwise,
VPNs/tunnels that ride over the links may see a too-small
MTU resulting in IPv6 fragmentation. Granted, doing better
than 1280 may be difficult for some links.

Thanks - Fred
[email-masked]

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of Bob Hinden
> Sent: Wednesday, April 20, 2011 2:26 PM
> To: Dan Wing
> Cc: [email-masked]; Bob Hinden; 'Brian E Carpenter'
> Subject: Re: PMTU blackhole detection
> 
> Dan,
> 
> > Ben Stasiewicz has done some research on IPv6 MTU problems,
> > 
> http://ripe60.ripe.net/presentations/Stasiewicz-Measurements_o
> f_IPv6_Path_MTU_Discovery_Behaviour.pdf
> > 
> 
> Very interesting.  A good next step would be to figure out 
> what caused each type of failure.
> 
> Bob
> 
> 
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