Subject: RValue/RGroup Properties.

From: Darin Herle <[email-masked]>
Date: Wed, 27 Sep 2000 20:03:10 -0700

I'm trying to understand the use of Reserve Value and Reserve Group
properties.

Can't you achieve the same result by having multiple values defined for the
same
property?  ie. specify a codec list for the "media" property of SDP.  What
were
the designers trying to achieve with RValue AND RGroup?

Thanks.

~Darin

---

From: Tom-PT Taylor <[email-masked]>
Date: Wed, 27 Sep 2000 23:27:21 -0400

For "Group" read "session" when you're using SDP.  The intent of
ReserveValue was to indicate the handling of exactly the sort of example you
give, where multiple values are specified for one property.  Is the MG
expected to be prepared to handle any one of them, or to select one return
it?  My favourite example of where it might be required to reserve resources
for multiple alternatives has been where it might have to switch on the fly
between e.g. G.729 and AVT-Tones encoding.  "Select one" would be where the
choice was between functional equivalents like G.729 and G.711.

ReserveGroup applies when multiple session specifications have been
provided. An example of when you might need this is when you want to present
the alternatives:
 - reserve for both G.729 and AVT-Tones, or
 - reserve for G.711 alone.
Depending on how ReserveGroup is set, the MG is being asked to keep its
options open by reserving resources for both session descriptions (with the
assumption that only one will be left when negotiations with the far end are
complete) or to select one of the alternatives (which is what the MG at the
far end would be asked to do).

> -----Original Message-----
> From: Darin Herle [mailto:[email-masked]]
> Sent: Wednesday, September 27, 2000 11:03 PM
> To: [email-masked]
> Subject: RValue/RGroup Properties.
>
>