Re: [MBONED] [Fwd: I-D Action:draft-eubanks-chimento-6man-00.txt]

[Greg Shepherd <gjshep at gmail.com>]

On Tue, Feb 24, 2009 at 4:07 PM, Dino Farinacci <dino at cisco.com> wrote:
>>>> The argument made by the draft authors is that since multicast
>>>> packets already have a UDP header with a checksum, there is no
>>>> additional benefit and indeed some cost to nodes to both compute and
>>>> check the UDP checksum of the outer (encapsulating) header.  However,
>>>> Consequently, IPv6 should make an exception to the rule that the UDP
>>>> checksum MUST not be 0, and allow tunneling protocols to set the
>>>> checksum field of the outer header only to 0 and skip both the sender
>>>> and receiver computation.
>>>
>>> It is worse than that for AMT. Since the control packets are encapsulated
>>> in
>>> an IGMP packet format. There is an IGMP checksum performed as well, then
>>> on
>>> top of that encapsulated in UDP, with the UDP checksum performed there
>>> too.
>>>
>>> So please note that the burden might be less in the control-plane, but it
>>> is
>>> less necessary to do UDP checksum as well in this case. I think you
>>> shouldn't deprecate the behavior in the spec, but outline how double
>>> check-summing is occurring in this case.
>>
>> Dino, I believe the current spec must be deprecated because it
>> specifically forbids a 0 checksum.
>>
>> Greg
>
> The AMT spec?
>
> Dino

No, sorry. The IPv6 UDP spec which does not allow 0 checksum.

Greg