Subject: RE: [Simple] Presence Data Model: Identifying services

From: "Nancy Greene (QC/EMC)" <[email-masked]>
Date: Thu, 23 Sep 2004 20:41:10 -0500

Paul said:
>I think the real problem in this case is not with the capability 
>approach. It is that the 'duplex' capability is underspecified. There is 
>no explanation of how a pair of half duplex endpoints (or one 
>half-duplex and one full-duplex endpoint) agree on who can talk.

> the case of the 'voice' capability, it is understood that having both 
>endpoints support voice isn't enough to support communication. There is 
>an SDP negotiation of codecs, etc. that either succeeds or fails. There 
>should be something similar for half-duplex.

I have been thinking about this too. When it is just a pair of terminals, each could use their own mechanism to not start an RTP session if it detects that the other end has started one first.

But don't we need the duplex info as an attribute in the sdp as well as in a feature tag? It may only apply to one of the media types negotiated.

Nancy

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