All things related to multicast

[Marshall Eubanks <>]

Michael Luby wrote:

> I'm always very confused by these discussions, probably because of my bias
> in terms of viewing multicast as just an underlying network efficiency
> enhancement instead of some kind of service that an end user should ever be
> aware of.  However, given my bias, I am really perplexed why it is
> considered the case that:
>
> (1) for SSM, the perception is that a miracle has to occur to discover the
> source address, but no similar miracle has to occur to discover the group
> address (which also has to occur for ASM). There are millions of ways to
> propagate the group address for ASM, or equivalently a (source, group
> address) for SSM, including building apps like SAP, SDR, etc. if you like
> that model, or webpages, etc.



I do no think that there is much difference here between ASM and SSM.


> (2) for many to many apps, people seem to think that ASM is ok.  I can see
> that SSM is more of a challenge in many people's minds for many-to-many
> apps, but even there I can see some pretty easy ways at the app level to
> support a many to many app using SSM that is at least as robust and
> efficient as using the existing underlying ASM implementations.


I think that many many to many apps will be driven to SSM for
security and deployment reasons.




> (3) webpages and other standard mechanisms viewed as terrible ways to
> disseminate info about content being delivered using multicast.  These
> mechanisms work quite well for unicast, and there are some extremely popular
> websites out there that get tens or hundreds of millions of hits a day, so
> why is this bad for multicast?  Again, this may my bias that I consider


It's not bad, it's just expensive.


> multicast an underlying network technology that should never even be exposed
> to the end user.  If you accept this bias, then there is fundamentally
> nothing different between what the presentation to the end user would be for
> multicast or unicast, and all the apps that need to be written on top of
> unicast for reporting also would need to be written for multicast to support
> reporting, ditto authentication, access, advertising the content, etc. So,
> if there seems to be a need to generate new ways of advertising info to end
> users for multicast, don't we need exactly these same new ways for unicast
> (again, this reasoning is only valid if you buy my bias that multicast and
> unicast should look the same to an app user, and multicast only provides
> underlying network efficiencies over unicast).


Actually, you do need other ways to publicize unicast broadcast sites; 
they have the exact same problems we do in that regard.

Please do not think that the existing unicast models for broadcasting 
are not broken, as they are.

Marshall


> Mike L
>
> -----Original Message-----
> From: 
>
> [mailto:]On
>  Behalf Of Marshall Eubanks
> Sent: Wednesday, August 07, 2002 8:21 AM
> To: Alan Crosswell; Kevin C. Almeroth
> Cc: 
>
> Subject: Re: IPv6 Multicast
>
>
> On Wed, 7 Aug 2002 10:09:54 EDT
>  Alan Crosswell 
> <>
>  wrote:
>
> > Can someone explain to me how one uses SSM to do something intrinsically
> > easy for ASM:  discover the existence of unknown sources?
> > /a
>
> The general answer to this
> is that you will discover SSM sources from a web site.
>
> The discovery of unknown web sites is left as an exercise to the reader :)
>
> Only people who
>
> a.) do not care about the size of their audience or
>
> b.) have very deep pockets
>
> would be happy with this reasoning.
>
> It seems clear to me that SSM will have SAP/SDR like guides, and I wonder
> that
> these have not been created yet.
>
> Marshall


--
                                 Regards
                                 Marshall Eubanks

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