Guru, The question is not only about the codec negotiation. It is mainly about the selection of the codec for effective b/w utilization in this scenario.
All these IP phones A,B and C support G.711 and G.729. And when A is supporting G.711, C also supports G.711 in this call. But, since C is in a different n/w with WAN interface, G.711 would be expensive which consumes more b/w. So, G.729 is the right codec here. Since, these endpoint terminals are not aware of the network configurations, C does not have intelligence to do this. What are the ways to select a proper codec here? Should the proxy server change the codec when the message is being sent? If proxy is doing this job, how can it trace what network interfaces the IP phones have? I think I have made the question clear. - sunil vatnal ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Wednesday, November 03, 2004 4:48 PM Subject: RE: [Sip-implementors] Codec negotiation > > Hi, > > With your Diagrammatic view, it is clear that proxy knows where user C > is and when user A sends an invite; proxy intercepts and intern sends an > invite to user C with user A media capabilities. If proxy does receive a > 200 ok from user C it just forwards the message to user A. (User C is > complaint with user A media capabilities). If this doesn't happen user C > proposes its own media capabilities and codec negotiation can take place > (Proxy may intercept with each or ip phones may have the intelligence to > carry out msg transfers without proxy in-between.) > > Regards, > Guru > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of > [EMAIL PROTECTED] > Sent: Wednesday, November 03, 2004 9:50 AM > To: [EMAIL PROTECTED] > Subject: [Sip-implementors] Codec negotiation > > Hi, > > When codec negotiation is taking place, > > - Since the endpoint terminals - usually IP phones - are not aware of > the > network configuration, How can the endpoint terminal (usually IP Phone) > decide one of its codec capabilities ? > > For example, there're 3 users on the network. > user A (IP phone, G.711, G.729 are possible, network 1.0.0.0) > user B (IP phone, G.711, G.729 are possible, network 1.0.0.0) > user C (IP phone, G.711, G.729 are possible, network 3.0.0.0) > Proxy Server (network 1.0.0.0) > > A ----- B (same network, LAN) > \ > P > | > | > C (different network, WAN) > > In case when the call between A and C is taking place and when the > bandwidth is concerned, > How would they know that G.729 should be used instead of G.711 because > they're not in the LAN environment ? > > Thanks > > /Jun > > _______________________________________________ > Sip-implementors mailing list > [EMAIL PROTECTED] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > > > > Confidentiality Notice > > The information contained in this electronic message and any attachments to this message are intended > for the exclusive use of the addressee(s) and may contain confidential or privileged information. If > you are not the intended recipient, please notify the sender at Wipro or [EMAIL PROTECTED] immediately > and destroy all copies of this message and any attachments. > > _______________________________________________ > Sip-implementors mailing list > [EMAIL PROTECTED] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
