SIP phone doesn't recognize that the caller has picked up the call

[Illini79]

SIP phone --> CUCM --> cube -->ITSP

hello all, when making calls to the PSTN over a SIP trunk the PSTN user answers the call but phone connected to CUCM never recognizes that the PSTN user has answered the call. The phone connected to CUCM continues to ring. SIP endpoints connected to the CUCM are unsuccessful but SCCP endpoints connected to the CUCM make calls successfully.  I've attached two packet captures and packet #10 in the good capture shows that cube sends out a second invite with SDP while in the unsuccessful packet capture  the cube sends out second invite with no SDP in packet#7 and the call fails.   It appears that the call is failing because cube sends out an invite without SDP and the ITSP doesn't know where to send traffic.  Can someone guide me in the right direction on this one.

[Mohammed al Baqari · Accepted solution]

Provider is sending 183 session progress to cube and cube is sending the same to cucm but no response is coming from cucm.

You need to enable PRACK on CUCM SIP trunk using SIP Profile and enable PRACK on CUBE as follow

In CUBE

dial-peer voice 1 voip

 voice-class sip rel1xx support "100rel"

OR

voice service voip

 sip

  rel1xx support "100rel"

In CUCM

1. In the CUCM Administration interface, go to Device > Device Setting > SIP Profile
2. Open the SIP profile used by a given SIP trunk.
3. Choose Send PRACK for all 1xx Messages from the SIP Rel1XX Options drop−down list.
4. Reset the SIP trunk profile for the given SIP trunk

[Illini79]

Mohammed you are awesome...!!!  That solved the initial problem.  Should I add the rel command for all my dial-peers? 

Now I have the problem that when PSTN phone try's to hang up the call, the phone attached to CUCM does not hangup.

[Dennis Mink]

Looking at the SDP Twillion want RTP terminate on 54.244.51.91 and you are wanting a connection on 192.168.15.101.

is your cube set up to have RTP flow around it, or flow through it?

is that routable? 

[Illini79]

Hello Dennis, I'm guessing the default behavior of the Cube is flow through and I haven't changed the default configuration. My global comcast IP is NATT'ed to my internal 192.168.15.101.