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

[Dave Thaler <dthaler at windows.microsoft.com>]

You don't need to do a "deprecate" per se to do this.  You just need
to do an "updates" as far as I know.

Another protocol that I believe would want a 0 checksum is if you
want to use UDP-ESP (RFC 3948) across a NAT64.

-Dave


> -----Original Message-----
> From: mboned-bounces at ietf.org [mailto:mboned-bounces at ietf.org] On
> Behalf Of Marshall Eubanks
> Sent: Tuesday, February 24, 2009 4:37 PM
> To: gjshep at gmail.com
> Cc: mboned at ietf.org
> Subject: Re: [MBONED] [Fwd: I-D Action:draft-eubanks-chimento-6man-
> 00.txt]
>
>
> On Feb 24, 2009, at 7:10 PM, Greg Shepherd wrote:
>
> > 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.
>
> Correct.
>
> Note that I do not think that it is appropriate to say that we are
> "deprecating" IPv6, or IPv6 UDP.
>
> We are adding flexibility that is needed to support applications,
> including (but not limited to)
> AMT. In most cases, checksums WILL still be required, and the spec
> will be unchanged. But in cases like this,
> where the flexibility is needed, it will be there.
>
> <Wearing no hats at all>
> Marshall
>
> >
> >
> > Greg
> > _______________________________________________
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