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

From: Scott Bradner <[email-masked]>
Date: Thu, 4 Apr 2002 09:23:12 -0500 (EST)

> 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.

I know of no widely deployed, well used, multicast service on the Internet.
There are a number of LAN or enterprise-level multicast applications but
not ISP-based ones that have had enough use to show that they can be
made to work operationally

> What you would you propose as an alternative to multicast?

I propose that we, in this group, not invent new applications but instead 
figure out how to ensure that existing applications work in times of
emergency. And I think that doing anything with multicast would be
inventing new applications.

That does not mean that people in the IETF should not work on multicast.
The SSM WG is doing just that.  But until we have evidence that multicast
services can and are deployed in ISPs we do not have any idea what 
problems to solve in the case of emergency.

Scott

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From: Alistair Munro <[email-masked]>
Date: Thu, 04 Apr 2002 18:49:10 +0100

Hi Scott,

Thanks for the clarification.

> made to work operationally

Yes, that was my feeling too. A set of applications running on IP for the
purpose of supporting the emergency services operationally within a closed
network would fall in the category of enterprise, possibly, and might have more
success. I think we would have to say do *not* use multicast to implement
emergency services if you are a commodity ISP.

> emergency.

I would limit the applicability of this to commodity ISPs. Possibly something
along the lines of:
    must turn on DiffServ (RFCs xxxx apply)
    take heed of RFC IntServ in DiffServ environment (sorry about choice of
words)
    indicative bandwidth allocations

I don't see why innovators can't be left to implement new applications for
closed emergency service networks, using multicast or not. I have been working
on specifying this sort of thing with SIP, mobility, and multicast - and it is
hard work... but there are applications out there. I'm sure we could write some
sort of best practice advice.

> And I think that doing anything with multicast would be

If the functionality we *think* is needed already exists, can we not draw
attention to it and its use as part of current practice? Without specifying
applications?

>   But until we have evidence that multicast services can [be] and are
> deployed in ISPs we do not have any idea what problems to solve in the case
> of emergency.

Before I came across this WG, I had a fairly simple-minded view of what an ISP
offering Internet services over a 3G commodity mobile network would have to do
to support services in an emergency and emergency services for the public and
professionals. From earlier analysis, we believed that multicast is apropriate
for special professional purposes. If you are saying that there are no ISP
supported multicast services that must be maintained in an emergency then I
agree, but I do not agree that multicast should not be used for certain
purposes - just surrounded by skull-and-crossbones for the unwary.

I will have to go back to the Baker and Folts drafts to see what I think the
wording should be.

Regards,

Alistair