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

[Ed Leatherman]

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
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