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

[Dino Farinacci <dino at cisco.com>]

Maybe Marshall, you should send this request to a wider list than just  
multicast people.

Dino

On Feb 25, 2009, at 3:45 AM, Marshall Eubanks wrote:

> On Feb 25, 2009, at 12:15 AM, Dave Thaler wrote:
>
> > 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.
>
> This plus LISP makes 2 protocols beyond AMT that need this. If you  
> know of others, please send them to the list.
>
> My feeling is that this is likely to be widely used, if it gets  
> through the process.
>
> Regards
> Marshall
>
>
> > -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
> > > > _______________________________________________
> > > > MBONED mailing list
> > > > MBONED at ietf.org
> > > > https://www.ietf.org/mailman/listinfo/mboned
> > >
> > > _______________________________________________
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> > > https://www.ietf.org/mailman/listinfo/mboned
>
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