Subject: ATM extensions to SDP - QoS parameters be in there

From: "Rosen, Brian" <[email-masked]>
Date: Mon, 14 Feb 2000 14:50:49 -0500

There is a small group of people working to extend SDP to describe
an ATM bearer.  For both MGCP and Megaco/H.248, SDP is the way to 
describe the characteristics of a bearer in a session, and if we 
want an ATM bearer, we need to do it with SDP.  In addition to the 
Media Gateway Control protocols, it would be nice if the same 
mechanism worked for SIP, which uses SDP for the same purpose.

A question has arisen which is architectural, and thus this message.
When you create an ATM connection, you specify addresses, and you
also specify QoS parameters.  The protocols that create the 
connections have both sets of parameters.  The question at hand
is, should SDP carry QoS parameters, as well as addresses and
bearer type (IP, ATM, ...)?  On the one hand:
	QoS is as much of a session specification as a codec choice
	It would be very expedient to have c= lines for the various 
		ATM QoS parameters because all users of SDP would then 
		be able to completely describe an ATM VC
	One (ATM) protocol is used to carry both sets of parameters,
		so why artificially split QoS and address info

On the other hand:
	We have shunted IP Qos to separate protocols -- IP QoS 
		parameters are not defined in SDP
	Generally speaking, QoS choices are made at one end, while 
		SDP is used primarily between peers to describe sessions

This issue may come up again in other contexts, so I'm soliciting 
advice from the larger group on this architectural question.

Brian
------------
Brian Rosen, Principal Engineer
Marconi (Formerly FORE Systems)
1000 FORE Drive, Warrendale, PA 15086
(724) 742-6826  mailto:[email-masked]

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From: Stephen Casner <[email-masked]>
Date: Mon, 14 Feb 2000 23:14:10 -0800 (Pacific Standard Time)

On Mon, 14 Feb 2000, Rosen, Brian wrote:
...
> 		SDP is used primarily between peers to describe sessions

It is accurate the no QoS parameters are currently specified in SDP,
but that doesn't mean there is no need for them.  We have defined some
private SDP extensions for QoS to use in our IP/TV application.

							-- Steve

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From: Dean Willis <[email-masked]>
Date: Wed, 16 Feb 2000 18:46:04 -0600

Yep, put em in. Can't really do the job without this info, as the Precept
people discovered independently.

--
dean

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On Behalf Of
> Rosen, Brian
> Sent: Monday, February 14, 2000 1:51 PM
> To: [email-masked]'
> Subject: ATM extensions to SDP - QoS parameters be in there
>
>