Subject: Re: [magma] WG Last Call: draft-holbrook-idmr-igmpv3-ssm-04.txt

From: Nidhi Bhaskar <[email-masked]>
Date: Thu, 5 Jun 2003 12:13:15 -0700 (PDT)

> Now, on the question whether the admin-scoped range for SSM should
> be within the SSM range of 232/8 or within the existing admin-scoped
> range of 239/8.
> RFC 2365 already defines 224.0.1.0-238.255.255.255 as
> "global scope", but this was before SSM (i.e., when 232/8 was
> allocated for VMTP transient groups :)
> Hence, it seems to me that you can go either way, by shifting the
> configuration compexity between extra SSM-range configuration and
> extra admin-scope configuration.
>
> My preference would be that the SSM admin-scope range is within the
> original SSM range (232/8), because of the substantial difference
> between ASM and SSM (compared to the difference between "scoped" and
> "non-scoped" multicast), and because it keeps things cleaner. In
> that case, you may need to add additional scope zone configuration
> only for your border routers; otherwise you may have to reconfigure
> all your routers AND hosts to support SSM within some subrange of
> 239/8.

I agree that a scoped multicast SSM range should be allocated.  This
reduces configuration required to enable SSM defaults. However,
carving one from 232/8 (say 232.239/16) may not be the better option.

I don't think Admin scoping is different between ASM/SSM. It is used
to restrict traffic to a certain topology by relying on the group
to which it is sent. For SSM we could reword that to -- restrict
traffic for all channels where the group falls under 239/8.

I think it is early enough to define a admin scoped SSM range within
239/8. Right now, most vendors likely require SSM to be explicitly
enabled & networks doing admin scoped SSM already configure an
additional admin scoped SSM range (e.g 239.232/16 or something else).
For this reason moving to a subrange of 232/8 is more work not less -
now boundary config also need updating.

Also, SSM deployments today happen by upgrading first/hop last hop
routers and the remaining topology thinks the group is Sparse. The
folks who are turning on SSM in the network may not be the same as
those that know/control the boundary configs. The consequences of not
updating a boundary to include 232.239/16 are worse than some routers
within the admin scope thinking 239.232/16 is Sparse.

Also, I like the idea that all admin scoped multicast falls under
239/8.

I admit that this is a very router specific view of things and does
not take into account requirements for hosts/apps.

Thanks,
Nidhi.

>
> Thanks,
> Pavlin
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From: Nidhi Bhaskar <[email-masked]>
Date: Thu, 5 Jun 2003 12:13:15 -0700 (PDT)

Thanks,
Nidhi.