Subject: Re: [Ieprep] a little homily - benefits of multicast

From: Scott Bradner <[email-masked]>
Date: Thu, 4 Apr 2002 08:30:43 -0500 (EST)

it seems to me that these two sentences are mutually exclusive

> I see multicast as an essential part of the solution. Current practice for
> using multicast in interactive real-time applications is a mystery to me.

we have no "running code" that multicast has any real use in the Internet -
if that is the case then how can multicast be "an essential part of the
solution"

scott

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From: Alistair Munro <[email-masked]>
Date: Thu, 04 Apr 2002 14:52:46 +0100

Hi Scott,

> we have no "running code" that multicast has any real use in the Internet -

I can't quite parse this, so excuse any misunderstanding. There are conferencing
applications based on multicast that I have used, and I am sure that you have
too. On the non-interactive side, there is content being distributed from
Internet2 sites using multicast - albeit experimental. Microsoft media server
distributes content using multicast.

What running code are you looking for specifically - have I missed your point?

However my point was that  I don't know what to refer to concerning best
practice on how to do conferencing using IP multicast.

> if that is the case then how can multicast be "an essential part of the

Layer 2 and layer 3 multicast is widely used in emergency/professional mobile
systems for several applications. I mentioned group calls and there are others.
Users of those systems would insist on having these applications on an Internet
platform. Whether these applications would use IP layer 3 multicast is a
reasonable question to ask. They could be implemented on some platforms using
the layer 2 capability (e.g. TETRA) but not, for example, in a GSM network.
802.11 is something else again. What you would you propose as an alternative to
multicast?

Regards,

Alistair

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From: Fred Baker <[email-masked]>
Date: Thu, 04 Apr 2002 09:54:45 -0800

>distributes content using multicast.

yes, and those are used in some enterprise environments. Scott is pointing 
out that there isn't much of this on the backbone. We know that there 
isn't, because few of the backbone operators enable multicast routing. They 
have had trouble with it and because they have not been able to obtain 
revenue from it, so the capability simply doesn't exist in their networks. 
Intersite multicast across the Internet mostly happens in tunnels.