Subject: [Megaco] Question concerning Dynamic Payload Type negotiation/configuration

From: Gunter Weiss <[email-masked]>
Date: Tue, 26 Aug 2003 16:13:13 +0200

Hello,

I have some basic questions on Dynamic PT negotiation within H.248/SDP:
-----------------------------------------------------------------------
   How is it considered in a H.248 controlled network to negotiate
   the Dynamic Payload type (used for DTMF relay a'la RFC2833)
   between the two ends (Media Gateways) via the MGC.
   In detail I'm interested to know, how will the first ADD request
   from the MGC to the originating Gateway look like?
   1.1
   Will the MGC already send a dynamic payload in the session description
   of the first Add request from MGC towards the Gateway?
   e.g.:
   MGC >> MG:
   m=audio $ RTP/AVP 8 96
   a=rtpmap:96 telephone-event/8000

   MG >> MGC:
   m=audio 10036 RTP/AVP 8 96
   a=rtpmap:96 telephone-event/8000

   1.1.1: What will be if the Gateway has another default PT for 
   let's say DTMF relay? Can it responsen than in the following way:

   MG >> MGC:
   m=audio 10036 RTP/AVP 8 97
   a=rtpmap:97 telephone-event/8000

   Or is it considered that the GW can always adapt the PT??

   1.2 If the MGC will send already two PTs in the m line , 
   will there be the ReserveValue set to true or is in this
   case the ReserveValue not considered at all as the Dynamic PT is
   a further specification, what the resource should be able to handle?

   MGC >> MG:

   MEGACO/1.0 [123.123.123.4]:55555
   Transaction = 11 {
    Context = $ {
       Add = DS0/1/1
       Add = $ {
          Media {
             LocalControl{
                Mode = ReceiveOnly,
                ReserveValue = true}; 
             Local{
   v=0
   c=IN IP4 $
   m=audio $ RTP/AVP 8 96
   a=rtpmap:96 telephone-event/8000
                  }
   }}}}

   1.3 Or is it not sent in the request from the MGC, but sent in the
   response from the MG to the MGC?
   e.g.
   MGC >> MG:
   m=audio $ RTP/AVP 8

   MG >> MGC:
   m=audio 10036 RTP/AVP 8 96
   a=rtpmap:96 telephone-event/8000

   or another possible way to report the capabilities:
   e.g.:
   MGC >> MG:
     m=audio $ RTP/AVP 8

   MG >> MGC:
     m=audio 3456 RTP/AVP 8
     a=sqn: 0
     a=cdsc: 1 audio RTP/AVP 8 96
     a=cpar: a=rtpmap:96 telephone-event/8000

If there are already scenarios on this topic please point me to it!

Thanks in advance,
	Gunter!
 
-- 
                            Gunter Weiss,  VS/NGE,  VND
    +--------V--------+     Competance Area Leader - Gateway Protocols
    |  A L C A T E L  |     callto: +49-711-821-41613 faxto : .-40247
    +-----------------+     mailto:[email-masked]

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