Subject: [ssm] Session Relaying in SSM: architectural aspects

From: Kostas Katrinis <[email-masked]>
Date: Sat, 07 Jan 2006 16:50:01 +0100

Hello all,

within the premises of my PhD work I am studying multi-source 
functionality over SSM.

Pertaining to supporting multiple sources within a single SSM session by 
using a session relay,
the related bibliography (at least to my knowledge) agrees to placing 
the relay service at the application
layer (due to many advantages not listed herein).

Now, assuming an application-layer relay service, the possibilities for 
placing the relays are two:

a) At group members
b)"Inside" the network, using dedicated "proxies" (like Zappala proposed 
in [1]).

Assuming that one does not want to go for a) (for instance because the 
worst case delay is twice as high
as the worst case delay when using SPTs as proved in Holbrook's thesis), 
the goal of my email is to ask, whether
there is any insight/consensus on how the architectural model will look 
like for the b) option.

Queries are for example of the type:

1) Who is going to provide the proxy (relay) service? Is it the ISP for 
all SSM groups or does any application provider
(like a gaming company or a videoconferencing company) have to develop 
its own service. Or just have a dedicated
provider for the service (e.g. like Akamai).

2) How many of the benefits of SSM are lost (e.g. source filtering), if 
one goes for the relaying solution.

Think of it as searching an answer to the question: "how good can the 
relay solution get without sacrificing the deployment
benefits of the SSM model (whatever the latter is supposed to mean)".

I would greatly appreciate any inputs, related work hints etc.

Thanks,
Kostas.

[1] Daniel Zappala, and Aaron Fabbri, Using SSM Proxies to Provide 
Efficient Multiple-Source Multicast Delivery 
<http://faculty.cs.byu.edu/%7Ezappala/pubs/ssm-gis01.pdf>. IEEE 
Globecom, Sixth Global Internet Symposium, Volume 3, pages 1590-1594, 
November 2001.

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From: Marshall Eubanks <[email-masked]>
Date: Mon, 9 Jan 2006 20:01:07 -0500

Are you familar with the AMT protocol ?

> as the worst case delay when using SPTs as proved in Holbrook's thesis),

Why is delay the primary metric here ? These are mostly broadcast or even
VOD precaching services, and delay is pretty irrelevent.  I would
argue that hop (regeneration) count
is a better metric. I  would also argue that P2P broadcasting is
likely to be an important player.

> there is any insight/consensus on how the architectural model will look

If I am understanding you, this is dealt with by AMT.
http://www.ietf.org/internet-drafts/draft-ietf-mboned-auto-multicast-05.txt

> provider for the service (e.g. like Akamai).

This is really more a business problem than a technical problem.

In the AMT proposal, this is provided primarily by ISP's, although if
I deploy the service
I would certainly allocate bandwidth to it. A decent question is, is
it intended to supplant or enhance native multicast ? (Very roughly),
if supplant, then Akamai or the source, if enhance, the ISP's.

In other, P2P type proposals (say, with BitTorrent), this is done at the edge.

> one goes for the relaying solution.

I am not sure why you can't source filter in AMT. Please explain.

> I would greatly appreciate any inputs, related work hints etc.

Hope all these questions are  useful.

> Kostas.

Marshall