Cisco Jabber doesn't send PRACK

[techToddler]

Hello Forum,

Trying to understand the below.

Call flow:

Jabber -> CUCM -> CUBE -> ITSP.

Invite to CUCM -> Invite to CUBE

100 Trying to Jabber <- 100 Trying to CUCM from CUBE

183 Progress -> CUBE and 183 Progress to CUCM

-> At this point CUCM sends a PRACK to CUBE and forwards that 183 to Jabber. However, Jabber doesn't send a PRACK and can hear the ring back very well. No matter if I change the SIP profile to accept rel1xx option the ring back is heard. 

I am wondering what the reason behind this would be. Do CUCM instruct something else to Jabber to play this ringtone? if yes what keywords are seen in the log to verify them? 

That 183 in progress sent to Jabber never received a response. Is that normal? I assumed it should receive a response. 

Appreciate your help.

[Steven L]

is something not working? 

in general Cisco SIP Endpoints do not send PRACK as far as i know. The default SIP image for phones is proprietary. I think if you put an MPP image on them, it probably does send PRACKs for compatibility reasons.

Jabber is completely proprietary and will only support SIP messages that CUCM expects

[techToddler]

Steve thanks for replying,

If that is the case, why 183 is forwarded to Jabber even? How does CUCM even know if the Jabber is ringing then?

Hope my question makes sense. 

Thanks. 

[Steven L]

without looking at your actual SIP messages, i am not sure what the 183 contains. is it the SDP?

the endpoint still needs the SDP since that is what notifies what CODEC, etc is to be used.

[techToddler]

yes, it contains SDP. 

Below is the one sent to Jabber. I changed IP and other details but the SDP has the info. 

SIP/2.0 183 Session Progress
Via: SIP/2.0/TCP 10.11.12.13:64407;branch=z9hG4bK00004dfe
From: "XXXXXXXXX" <sip:XXXXXXXXXX@10.47.37.30>;tag=9c2dcd1acb3d0006000000af-000018ab
To: <sip:91YYYYYYYYYY@10.7.3.4>;tag=782970~dfee80d0-154f-4def-93f5-9e3cdd13bc26-46454726
Date: Mon, 22 Apr 2024 15:16:23 GMT
Call-ID: 9c2dcd1a-cb3d0003-0000486f-00007ef6@10.22.22.33
CSeq: 101 INVITE
Allow: INVITE, OPTIONS, INFO, BYE, CANCEL, ACK, PRACK, UPDATE, REFER, SUBSCRIBE, NOTIFY
Allow-Events: presence
Server: Cisco-CUCM12.5
Call-Info: <urn:x-cisco-remotecc:callinfo>; security= Unknown; orientation= to; gci= 2-36243; isVoip; call-instance= 1
Send-Info: conference, x-cisco-conference
Remote-Party-ID: <sip:+XXXXXXXXX@10.22.22.33>;party=called;screen=no;privacy=off
Contact: <sip:91YYYYYYYYYY@10.22.22.33:5060;transport=tcp>
Content-Type: application/sdp
Content-Length: 274

v=0
o=CiscoSystemsCCM-SIP 782970 1 IN IP4 10.22.22.33
s=SIP Call
c=IN IP4 X.X.X.X
b=AS:24
t=0 0
m=audio 22382 RTP/AVP 18 101
a=ptime:20
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
m=application 0 UDP/UDT/IX *

When this is sent out, I am not getting a reply back from Jabber even though the SIP profile is updated to send PRACK if 183 contains SDP. 

The only message that is sent after this is 200 Ok which is from the CUBE after accepting the call. 

Thanks. 

[Roger Kallberg]

This is as @Steven L wrote normal operations of Jabber. Is the lack of response cause of any issue(s)?

[techToddler]

No, the call works. I am trying to understand why there was no response from Jabber

[Roger Kallberg]

As @Steven L wrote Jabber, or any other Cisco soft phone client, doesn’t respond with PRACK. It’s as simple as that.

[Steven L · Accepted solution]

for your SIP profile, you said you configured it to send PRACK..

please note that this is a "Trunk Specific Configuration"

[techToddler]

Got it. I overlooked that heading. Thanks Steve and everyone.