[cisco-voip] question(s) about SIP early media

[Ed Leatherman]

Hi Brian,

Here's what the signalling looks like, apologies for the formatting.

No.     Delta       Time        Source                Destination
Protocol Info
      1 0.000000    0.000000    Vidyo Server          CUCM
 SIP/SDP  Request: INVITE sip:83045551212 at CUCM        | , with session
description
      2 0.001193    0.001193    CUCM                  Vidyo Server
 SIP      Status: 100 Trying |
  RTP from MTP to Vidyo starts here
      9 0.273383    0.274576    CUCM                  Vidyo Server
 SIP/SDP  Status: 183 Session Progress | , with session description
     47 0.751382    1.025958    CUCM                  Vidyo Server
 SIP      Request: UPDATE sip:Vidyo Server  :50600;transport=UDP |
     48 0.000829    1.026787    Vidyo Server          CUCM
 SIP      Status: 200 OK |
    707 13.100773   14.127560   Vidyo Server          CUCM
 SIP      Request: CANCEL sip:83045551212 at CUCM       :5060 |
    708 0.000478    14.128038   CUCM                  Vidyo Server
 SIP      Status: 200 OK |
    710 0.004368    14.132406   CUCM                  Vidyo Server
 SIP      Status: 487 Request Cancelled |
    711 0.000756    14.133162   Vidyo Server          CUCM
 SIP      Request: ACK sip:83045551212 at CUCM        |


On Tue, Oct 15, 2013 at 8:25 AM, Brian Meade (brmeade) <brmeade at cisco.com>wrote:

>  Ed,****
>
> ** **
>
> It will probably be much easier for use to follow the call flow if you
> could send the actual SIP messaging for one of the calls.****
>
> ** **
>
> Prack is really only used in response to a 180 Ringing with SDP or a 183
> Session Progress with SDP.  That’s where early media gets established.****
>
> ** **
>
> Brian****
>
> ** **
>
> *From:* cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] *On Behalf
> Of *Ed Leatherman
> *Sent:* Tuesday, October 15, 2013 8:19 AM
> *To:* Cisco VOIP
> *Subject:* [cisco-voip] question(s) about SIP early media****
>
> ** **
>
> I'm trying to troubleshoot what I think is an early media problem on a SIP
> trunk between CUCM 8.6 and a video conferencing system (Vidyo). If the
> Vidyo system tries to dial long distance, it does not get the audio prompt
> for the authorization code, which comes in from our long distance carrier
> prior to the call being established.****
>
> Audio is OK for local calls once the call is established.****
>
> ** **
>
> I don't have direct access to the vidyo side. so I took a few packet
> captures at the CUCM side to try and puzzle out what is going on.****
>
> ** **
>
> Vidyo sends SDP info immediately in its Invite message, and CUCM begins to
> send back audio from the MTP right away. Does CUCM need to send a PRACK
> here, or is the Status 100 reply from CUCM sufficient?****
>
> ** **
>
> CUCM also responds with it's own 183 session progress message back that
> includes it's own SDP info. I never see a PRACK back from Vidyo, nor do I
> get audio. Would this imply that vidyo is not participating in the early
> media?****
>
> ** **
>
> For a local call, vidyo does eventually start sending me audio when the
> session is completely established.****
>
> ** **
>
> On the CUCM side for the SIP trunk profile, I have Early Offer support for
> voice and video calls checked and SIP Rel1XX options set to send PRACK for
> all 1xx messages (tried both settings though)****
>
> ** **
>
> I'm asking my internal customer that owns the vidyo system to contact
> vidyo tech support, but I figured I'd see if any of you SIP gurus had an
> opinion :)****
>
> ** **
>
> --
> Ed Leatherman****
>



-- 
Ed Leatherman
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