Subject: [Speechsc] What is the scope of MRCPv2 session

From: santhanakrishnan <[email-masked]>
Date: Wed, 07 Jun 2006 11:20:40 +0530

Hi,

            The relationship between SIP dialog, MRCP session is not clearly
or explicitly stated in the draft.     

I have given some of the snippets from the "draft-ietf-speechsc-mrcpv2-09"
each of which is leading to different interpretations. Even "2.1
Definitions" section does not capture these items. Any amount of clarity
would be appreciated. 

>From page 10.

   A separate MRCPv2 session is

   needed to control each of the media processing resources associated

   with the SIP dialog between the client and server.  Within a SIP

   dialog, the individual resource control channels for the different

   resources are added or removed through SDP offer/answer carried in a

   SIP re-INVITE transaction.

For each resource there has to be a separate MRCP session?

>From page 29

   All MRCPv2 requests, responses and events MUST contain the Channel-

   Identifier header.  The value is allocated by the server when a

   control channel is added to the session and communicated to the

   client by the "a=channel" atribute in the SDP answer from the server

   The header value consists of 2 parts separated by the '@' symbol.

   The first part is an unambiguous string identifying the MRCPv2

   session.

   Please refer to page 163

   S->C:

          SIP/2.0 200 OK

          To:MediaServer <sip:[email-masked]>

          From:sarvi <sip:[email-masked]>;tag=1928301774

          Call-ID:a84b4c76e66710

          CSeq:314163 INVITE

          Contact:<sip:[email-masked]>

          Content-Type:application/sdp

          Content-Length:131

          v=0

          o=sarvi 2890844526 2890842809 IN IP4 126.16.64.4

          s=SDP Seminar

          i=A session for processing media

          c=IN IP4 224.2.17.12/127

          m=application 32416  TCP/MRCPv2

          a=channel:32AECB23433801@speechsynth

          a=cmid:1

          m=audio 48260 RTP/AVP 0

          a=rtpmap:0 pcmu/8000

          a=sendonly

          a=mid:1

          m=application 32416  TCP/MRCPv2

          a=channel:32AECB23433802@speechrecog

          a=cmid:2

          m=audio 48260 RTP/AVP 0

          a=rtpmap:0 pcmu/8000

          a=rtpmap:96 telephone-event/8000

          a=fmtp:96 0-15

          a=recvonly

          a=mid:2

Each resource control channel describes a separate session?

>From page 54

   If the synthesizer and recognizer resources are part of the same

   MRCPv2 session, they can be optimized for a quicker kill-on-barge-in

   response if the recognizer and synthesizer interact directly.

Multiple resources can there be in a MRCP session?

>From page 63

      For implementations where a single recognition resource does not
support

   both modes, or simultaneous normal and hotword recognition is

   desired, the two modes can be invoked through separate resources

   allocated to the same SIP dialog (with different MRCP session

   identifiers) and share the RTP audio feed.

Can multiple MRCP sessions be there in the same SIP dialog?

>From page 8

   MRCPv2 uses SIP and SDP to create the client/server dialog and set up

   the media channels to the server.  It also uses SIP and SDP to

   establish MRCPv2 control sessions between the client and the server

   for each media processing resource required for that dialog.  The

   MRCPv2 protocol exchange between the client and the media resource is

   carried on that control session.

Again does each resource control channel describe a separate session?

Regards,

Santhanakrishnan;

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