SIP Messages | missing "Ringing"

[sarahr202]

Hi everybody,

I am starting on IP telephony. Here is my lab set up: ( I am using soft phone  X lite)

10.10.10.4( EXT:2000)-----10.10.10.10(CUCM)-----10.10.10.5(EXT:2001)

I am using SIP for signalling.  EXT 2000 calls  EXT 2001, I can see SIP messages are relayed to EXT:2001 but I do not see any " any ringing " message coming from EXT 10.10.10.5

I also noticed that EXT 2001 informs CUCM during registration it can understand following SIP messages:

SUBSCRIBE, NOTIFY, INVITE, ACK, CANCEL, BYE, REFER, INFO, MESSAGE

Below you can see SIP messages are relayed to 10.10.10.5 ( EXT: 2001) but EXT 2001 did not send " Ringing" message . I did not hear any ringing either.

EXT 2001 does not send ringing message because it does not support,it is missing in the supported message? If yes, what  kind of phone is this if it does not support that important message ? :)

thanks.

[Vivek Batra]

First of all, Supported header doesn't need to include 180 Ringing since Supported includes only SIP methods and 180 Ringing is a SIP response, not a SIP method.

I don't think there would be any terminal in the world not supporting 180 Ringing since its come under basic feature as minimum capability need to be supported by any SIP UA.

In the above call flow, I can see one UDP message flowing from 2001 to call manager but not sure its content. Somehow 2001 is not able to accept the INVITE hence call manager is keep re-transmitting INVITE message to 2001.

One more point to notice is INVITE from call manager to 2001 is without SDP. If 2001 phone is third party SIP phone, it could be a issue. Many third party SIP phones (not having standard SIP stack) doesn't behave as per RFC 3264 with respect to delayed offer.

Both phones viz 2000 and 2001 are Cisco SIP phones?

Are you able to make call in reverse direction viz from 2001 to 2000?

Can you please share the SIP trace including SIP registration from both phones, call from 2000 to 2001 and from 2001 to 2000?

Thanks

Vivek

[sarahr202]

Hi Vivek

EXT 2000 ( 10.10.10.4) registers with CUCM

EXPANDED:

EXT2001 ( 10.10.10.5) registers with CUCM:

Expanded:

EXT 2000 calls EXT 2001 :

EXPANDED:

CUCM relays it to EXT 2001 which does not response:

#####################

EXT 2001 calls EXT 2000 , but met with the same result:

EXPANDED:

###########################

Much appreciated!!

EDIT:

Expanded (invite) from ext 2000 to CUCM:

[Vivek Batra · Accepted solution]

Would have better if shared actual wireshark traces. Anyway at this first sight, seems not having early offer on UAS side might be the issue.

SIP profile is having parameter to enable 'Early offer support for voice and video calls'. This parameters works great over SIP trunk. I'm not sure if this is applicable for devices too. Let's give a hit. Enable this parameter under SIP profile and assign this SIP profile to both phones (2001 and 2002).

Thanks

Vivek

[sarahr202]

I did try to attache file , it won't let me attach "pcapng" file. I will try " early support for voice and video calls" and come back.

Much appreciated!!