Hi, SIP is peer to peer and to have media gateway among endpoints which exists over different networks, there should be some global policy negotiated among all endpoints so that media will be always routed through that specific media gateway. I think it is againt the SIP philosophy.
Simple Solution to this problem within the scope of SIP signaling--- -------------------------------------------------------------------- As a local policy, each endpoint which is not aware of its n/w bandwidth, should send SIP OPTIONS request to its SIP PROXY server ( which may be outbouns proxy also) to discover the b/w to be used. This SIP Proxy must know the network configuration and should reply back to the UAC with the b/w. SIP OPTIONS can be sent to SIP Proxy server. Refer RFC 3261 Page 66 Section 11 Carefully go throgh Sectioon 11 to know how to target OPTIONS request to Proxy Server. -------------------------------------------------------------------- I think it is the most feasible solution within the scope of the SIP philosophy. Best Regards, Deepak kumar Sr. Software Engg. Global Edge Software Ltd. Bangalore, India +91-9448492335 ----- Original Message ----- From: "Avasarala Ranjit-A20990" <[EMAIL PROTECTED]> To: "???" <[EMAIL PROTECTED]>; "'sunil vatnal'" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Wednesday, November 03, 2004 5:48 PM Subject: RE: [Sip-implementors] Codec negotiation > Hi > proxy need not have a media function since media does not go through proxy. > But since proxy is aware of network configuration, media can be routed through media server or gateway. > So for this to happen, there should be some signalling mechanism between media gateway (server) and proxy. > > So whenever there is a difference in network configuration, proxy should route the media data through media server. > > For this proxy needs to inform User Agents to send their media data to media server instead of directly sending to other user. > > I am not aware of any standard or spec that says about proxy server getting network info. > > Regards > Ranjit > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Sent: Wednesday, November 03, 2004 5:28 PM > To: Avasarala Ranjit-A20990; 'sunil vatnal'; [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED] > Subject: RE: [Sip-implementors] Codec negotiation > > > Ranjit, > > The media part is transcoded only if the proxy server has media function embedded. Let's assume that the proxy server doen not have media function and it's aware of some of network configuration. Two questions here; 1. Is it really O.K that the proxy server would change some information in SDP body of SIP INVITE message ? > - Back to the A and C case > 1) A sends INVITE + SDP to the proxy server. > (SDP -> m: audio 3000 RTP/AVP 0 4 18, --> 0:g.711, 4:g.723, > 18:g.729) > 2) The proxy server forwards the INVITE + "modified" SDP > (SDP -> m: audio 3000 RTP/AVP 4 18, --> now g.711 has been > removed since the "C" is out of the local network) > ==> Is it really possible ? As far as I know, the proxy server is not aware of "SDP" unless it's working as an B2BUA... > 3) B responses with 200 OK > > 2. Actually, no one can understand the network configuration except the "Router". The real WAN interfaces are managed by the router of each network and neither the proxy server or IP phone knows that specific information of the WAN interfaces. > - Is there any kind of standard specifications (or implementation > guidelines) that a proxy server could get network interface information such as trunk type and bandwidth from the network ? > > Regards, > Jun > > -----Original Message----- > From: Avasarala Ranjit-A20990 [mailto:[EMAIL PROTECTED] > Sent: Wednesday, November 03, 2004 6:01 PM > To: sunil vatnal; [EMAIL PROTECTED]; [EMAIL PROTECTED]; sip- [EMAIL PROTECTED] > Subject: RE: [Sip-implementors] Codec negotiation > > Hi Sunil > > here since proxy is aware that user C is in a different network, it should communicate with user C using G.729. so the media part is /transcoded/ before it goes to user C. > So the media server, transcodes from G.711 to G.729 for C and vice versa for A. > > > Regards > Ranjit > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:sip-implementors- [EMAIL PROTECTED] On Behalf Of sunil vatnal > Sent: Wednesday, November 03, 2004 2:04 PM > To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; sip- [EMAIL PROTECTED] > Subject: Re: [Sip-implementors] Codec negotiation > > > 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 > > _______________________________________________ > 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
