PMTUD broken with

Fernando Gont fernando at
Fri Feb 4 04:37:09 CET 2011

Hi, Daniel,

On 02/02/2011 07:24 p.m., Daniel Roesen wrote:
>> I do worry that the ipv6 universe will be 1280 vs the 1476/1500 in v4 land...

Actually the 1280 value in v6 should be compared with the 68B value in
v4 -- these are the minimum MTUs for each technology.

> The DOCSIS model uses RAs with M=1 O=1 and no prefix advertisement on
> the DOCSIS link between the CMTS and the CPE router to enforce stateful
> DHCPv6. Reading above paragraph, we cannot advertise a MTU >1500 there
> to cover for e.g. DS-Lite encaps overhead to make reasonable sure that
> AFTRs don't need to reassemble tunnel packets.

Sorry, I don't follow. You want to advertise an MTU>1500 on Ethernet?

Fernando Gont
e-mail: fernando at || fgont at
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