Subject: RE: [Megaco] Reserve Value and Reserve Group

From: "Tom-PT Taylor" <[email-masked]>
Date: Wed, 2 Jan 2002 14:24:11 -0500

A "property group" is the same as a session description.  ReserveGroup=true
says to reserve resources to support all of the session descriptions
presented.

ReserveValue=true definitely says that if multiple payload types are
presented on the same m= line, resources should be reserved for all of them.
The grey area is if there are multiple m= lines within the same session
description.  I propose the interpretation that ReserveValue=true reserves
all resources within the same session description.

I believe a further interpretation is needed as follows:

  ReserveValue=true, ReserveGroup=false, multiple session descriptions
presented:
  --------------
 means that the MG chooses its preferred session description, then reserves
all resources specified therein.

  ReserveValue=false, ReserveGroup=true, multiple session descriptions
presented:
  --------------
 means that the MG reserves resources for every session description, but
within each session description, where any m= line presents alternative
payload types, the MG chooses just one of the alternatives. 

I suspect it may be simpler to use the FID mechanism
(draft-ietf-mmusic-fid-05.txt) when it is finished.

As for the missing s=, o=, and t= lines, RFC 3015 makes them optional in the
MGC-to-MG direction.

-----Original Message-----
From: Sudhir Kumar Appana [mailto:[email-masked]]
Sent: Saturday, December 29, 2001 1:27 AM
To: [email-masked]
Cc: Sudhir (E-mail)
Subject: [Megaco] Reserve Value and Reserve Group

Hi,
In the RFC 3015, following is given in section 7.1.8 (Local and Remote
Descriptors):
"If ReserveGroup is true, the MG reserves the resources required to
support any of the requested property group alternatives that it can
currently support.  If ReserveValue is true, the MG reserves the
resources required to support any of the requested property value
alternatives that it can currently support."

In the above statement, I want to know "what is property group and what is
property value". Where can I get more information on this. I referred
SDP RFC 2327, in that Session level Description and Media level Description
are differentiated. But I could not conclude from this.

In RFC 3015 Appendix-A section-A.1.2 Step-12, Local Descriptor defines two
Session level descriptions. Can anybody mail me how can I interpret this,
as property groups or as property values. I will be happy, if somebody
explains this with some example packets.

One more doubt regarding SDP Paramters:
In SDP RFC 2327, it is given that following fields are mandatory:
For 'Session description':
v=  (protocol version)
o=  (owner/creator and session identifier).
s=  (session name)
For 'Time description':
t=  (time the session is active)

For 'Media description':
m=  (media name and transport address)

But in call flows given in RFC 3015 Appendix A and in 'draft-madhu-megaco-
callflows-00.txt', I haven't found fields 'o=' and 's='. Are this fields are
not required.

Thanks,
Sudhir

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---

From: "Usha Iyer" <[email-masked]>
Date: Thu, 3 Jan 2002 10:01:14 +0530

Hi Tom, All

    Section  6.98 of  AVD-2128 doc ( H248IG) states that
--------------------
A Stream Descriptor specifies a single bi-directional media stream and so a
single session description MUST NOT include more than one media description
("m=" line).  Any additional media streams for a termination must appear in
distinct Stream Descriptors.
-----------------------
      Due to the above restriction ,you can't have multiple "m=" lines in
one session desc.
       One ques:  How do u resolve ReserveValue = True and also ReserveGroup
= True

Regards
Usha

---

From: "Usha Iyer" <[email-masked]>
Date: Thu, 3 Jan 2002 10:01:14 +0530

Hi Tom, All

Regards
Usha