Hi to everyone,
We have SIP Cisco IP Phone <-> CUCM <-> SIP Trunk <-> CUBE <-> SIP Trunk <-> ITSP.
- When PRACK is enabled and Cisco IP Phone makes a call to a specific mobile destination, Cisco Phone does not hear Ring Back Tone.
- When PRACK is disabled in CUCM SIP Profile and the same call is made then RBT is played locally from the phone.
PRACK is mandatory and agreed with the provider so it must be enabled both in CUCM and CUBE.
Provider says that no matter if they send us 183 Session Progress if they send us afterwards 180 Ringing then we must play the tone locally.
As far as I know and please correct me if I'm wrong:
- If 183 Session Progress with SDP is send then cisco phone waits to hear tone from ITSP.
- Also if 180 Ringing is received but there are no incoming media packets then cisco phone must play local RBT.
Can someone please advice?
Below are the outputs from the packet captures in CUBEs internal and external interfaces where Cisco Phone makes a call to ITSP and PRACK is enabled in CUCM and CUBE.
Below are the outputs from the packet captures in CUBEs internal and external interfaces where Cisco Phone makes a call to ITSP and PRACK is disabled only in CUCM SIP Profile.
Hi TechLvr,
I tried with "Send PRACK if 1xx Contains SDP" in SIP Profile of SIP Trunk in CUCM but nothing changed.
The obvious would be that CUCM should not send PRACK in 180Ringing without SDP but below is the debug from CUBE where you can see that CUCM continuous to send PRACK.
The command voice-class sip rel1xx system is the default one of the dial-peer which was revealed from "show run all". There is no manually entered command in dial-peer regarding rel.
Below you can see the debug ccsip messages output from a working B number which has RBT played from the ITSP side and a non working B number which has NO RBT either from ITSP side or locally.
Both calls have PRACK enabled end to end (CUCM-CUBE).
In the good scenario ITSP sends RBT after 183 with SDP.
In the bad scenario ITSP does not send RBT after 183 with SDP. Then after 180Ringing is received from ITSP, although RBT should be played locally from the phone this is not happening.
As said in my original post if PRACK is disabled for the bad scenario on CUCM side then RBT is locally played from the phone. Keep in mind that PRACK is mandatory and cant be disabled in the production. It was done only for testing purposes.
Debugs from both good and bad scenarios are attached.
Working Scenario:
From the logs, it seems like when the ITSP sends 180 Ringing with "Require: 100rel" to the CUBE, and the CUBE sends a PRACK to the ITSP as expected.
The CUBE then sends 180 Ringing with "Require: 100rel" to CUCM, and the CUCM sends a PRACK back to the CUBE.
ITSP sends 200OK to the CUBE for the PRACK message.
CUBE sends 200OK to the CUCM for the PRACK message.
Non-working Scenario:
ITSP send 180 Ringing WITHOUT "Require:100rel" to the CUBE. The CUBE does NOT send a PRACK to the ITSP as the ITSP did NOT request a PRACK.
The CUBE then sends 180 Ringing with "Require: 100rel" to CUCM, and the CUCM sends a PRACK back to the CUBE.
CUBE sends 200OK to the CUCM for the PRACK message.
I believe the issue is that the ITSP does not consistently send "Require:100rel" in the 180 Rining message to the CUBE.
I suggest you ask the ITSP to look into this on their end.
Also, I noticed something strange in your non-working call logs. For example, in the initial INVITE from the CUBE to the ITSP, the Via header says "ITSP" instead of "CUBE-EXTERNAL-IP". In that same Invite w/ SDP the connection header shows "c=IN IP4 ITSP" instead of "c=IN IP4 CUBE-EXTERNAL-IP". I think there are two possible reasons. Either you made a mistake while censoring the IP addresses in the non-working call logs, or the non-working calls use a specific dial peer with a SIP profile that messes up the SIP messages. Can you check that?
Screenshot below shows the difference between the working and non-working scenarios.
Screenshot below shows the errors you probably made while censoring or possible issues with the CUBE configs.
