Subject: [ssm] draft-chesterfield-avt-rtcpssm

From: Toerless Eckert <[email-masked]>
Date: Mon, 4 Jul 2005 13:09:07 -0700

Hi folks.

What happened to subject draft ? We really need that type of RTCP for SSM
feedback to get some standardization and move on on SSM ? Is it just timed out
and nobody cares ? How can it be revived ?

Thanks
    Toerless

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From: Colin Perkins <[email-masked]>
Date: Mon, 4 Jul 2005 21:39:32 +0100

> and nobody cares ? How can it be revived ?

The latest version was draft-ietf-avt-rtcpssm-08.txt, which expired  
recently. I'm hoping a revised draft will be available in time for  
the next meeting - there has been some discussion on the draft in the  
last few days.

Colin

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From: Toerless Eckert <[email-masked]>
Date: Mon, 4 Jul 2005 15:01:57 -0700

> the next meeting - there has been some discussion on the draft in the  

Thanks, Colin,

Just as a general critique: I don't think that a draft like
draft-ietf-avt-rtcp-feedback should go forward without specifically
detailing whether or how it supports ASM and/or SSM multicast. This draft
only refers to multicast, and that is just not sufficient anymore.

Thanks
    Toerless

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From: Colin Perkins <[email-masked]>
Date: Mon, 4 Jul 2005 23:09:44 +0100

On 4 Jul 2005, at 23:01, Toerless Eckert wrote:
>>> What happened to subject draft ? We really need that type of RTCP
>>> for SSM feedback to get some standardization and move on on SSM ?  
>>> Is it
>>> just timed out and nobody cares ? How can it be revived ?
>>

The draft is titled "RTCP Extensions for Single-Source Multicast  
Sessions with Unicast Feedback", and makes an explicit distinction  
between ASM and SSM throughout. I'm not sure exactly what else you  
think it should say?

Colin

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From: Toerless Eckert <[email-masked]>
Date: Mon, 4 Jul 2005 15:41:54 -0700

> between ASM and SSM throughout. I'm not sure exactly what else you  

It's a generic problem of all drafts and RFC that only loosely refer to
"multicast". "multicast" is not an explicit service anymore. Documents need to
refer to ASM multicast and/or SSM multicast to make it clear which of those they
have considered.

Thanks
    Toerless

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From: Colin Perkins <[email-masked]>
Date: Tue, 5 Jul 2005 00:16:16 +0100

> refer to ASM multicast and/or SSM multicast to make it clear which  

Sure, I understand that. But from my reading, this draft *does* refer  
explicitly to SSM rather than just "multicast" -- what needs to be  
changed?

Colin

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From: Toerless Eckert <[email-masked]>
Date: Thu, 7 Jul 2005 08:49:30 -0700

On Thu, Jul 07, 2005 at 10:21:15AM +0200, Joerg Ott wrote:
> To add to this, draft-ietf-avt-rtcpssm also discusses how
> non-aggregatable RTCP messages shall be treated.  Thus, it is explicitly
> designed to also support RTCP feedback in SSM environments--obviously
> at some loss of damping efficiency but what would you expect if you
> double propagation delay.

> only refers to multicast, and that is just not sufficient anymore.

eg: different draft! But one which i think relates quite a bit to the
issue at hand as well and should not become an RFC without explicitly
mentioning ASM and SSM (which it does not).

I for once fail to easily determine from the claims of support whether
one could use the mechanisms described therein with SSM (i think not),
nor do i understand easily whether it would be possible to use them with
SSM if combined with draft-ietf-avt-rtcpssm without further extensions.

And this is probably not the only draft about other RTCP stuff. For
all of it, the rule applies: In the real world, customers want to move
to SSM and it needs to be easy to determine applicability  from the
drafts claims !

Cheers
	Toerless

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From: Toerless Eckert <[email-masked]>
Date: Thu, 7 Jul 2005 15:09:05 -0700

On Thu, Jul 07, 2005 at 05:57:00PM -0400, Julian Chesterfield wrote:
> Toerless,
> 
> On 7 Jul 2005, at 11:49, Toerless Eckert wrote:
> 
> Please read the latest version of the draft. The introduction goes into 
> great detail about the ASM and SSM communication models, and associated 
> protocols.

% grep SSM draft-ietf-avt-rtcp-feedback-11.txt
<nothing>

% grep ASM draft-ietf-avt-rtcp-feedback-11.txt
<nothing>

hmmm...

> again, the introduction discusses three scenarios where the mechanism 
> would be appropriate. The first scenario is an SSM group. The scheme is 
> designed towards SSM groups in particular on the basis that an SSM 
> group can support multicast downstream, and unicast back to the source.

> What extensions would be required to make this work over an SSM 
> architecture?

re-read my email ? ;-)) I am concerned about any other draft extending
the use of RTCP (and that happens quite a bit via for example 
as i mentioned "draft-ietf-avt-rtcp-feedback" and other relying on
that draft, like RTP retransmissions) - All those folks i think are
aboslutely NOT considerin whether and/or how their stuff would work
with multicast SSM, and i am saying that each draft that extends RTP
needs to explicitly mention it's aplicability claim to ASM and SSM
(claims to support ASM and/or SSM), and NOT claim anymore simply
"does also support multicast").

Cheers
	Toerless

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From: Toerless Eckert <[email-masked]>
Date: Thu, 7 Jul 2005 23:42:35 -0700

On Fri, Jul 08, 2005 at 08:28:32AM +0200, Magnus Westerlund wrote:
> Hi Toerless and Julian,
> 
> You seem to be talking around each other. What I understand is that you 
> want the following:
> 
> Toerless requests Joerg (author of RTCP FEEDBACK AVPF draft) to clarify 
> which parts of the mechanisms that applies to ASM and which is also 
> usable by SSM.
> 
> Julian request Toerless to review draft-ietf-avt-rtcpssm-08 which is the 
> latest version of the draft, although expired and provide comments. 
> Google after it and you will find it.

Sure.

> Have I understand this correctly?

Aah, you're taking all the fun out of it. This was classical theater
where two actors talk monologes over each other ;-)
> 
> In regards to AVPF is not specific to either ASM or SSM it can be used 
> in either models. However it does require you to implement the SSM RTCP 
> solution to be able to use it.

See, that is a sentence i think should be in that draft. Of course it
would require a reference to RTPSSM, but that's exactly what would make
me happy ;-)

> Please note that AVPF is an approved but not yet published. Thus making 
> any changes are problematic and only really broken thing or minor 
> editorial things are adressable.

*sigh*. I have been trying to get the notion into the bloody IETF/IESG review
process that "supports multicast" is a term in drafts that should be
unacceptable, but instead every draft should mention as appropriate ASM
or SSM.

But if you as someone who probably had more time to understand the potential
interaction of the AVPF and RTCPSSM think that they should be combine
with each other flawless and without need for further specs, 
then i am at least less nervuous on that front, because in the end it's
about being able to leverage all RTP/RTCP progress while still deploying
SSM...

Thaks a lot !

   Toerless

> Cheers
> 
> Magnus Westerlund
> 
> Multimedia Technologies, Ericsson Research EAB/TVA/A
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