SIP Phone 6921 doesn't send DTMF to BiB recorder

[sergio.castelani]

Hi friends!

Our  company is developing a call recorder based on built-in-bridge  technology. This recorder uses the DTMF (RFC-2833) signals from the  telephones to activate some custom processing. We did all development using phone 7911 and CUCM 8.6 as a test base, getting awesome results.

However, we started testing other phones with BiB technology and got stuck at Phone 6921, because we couldn't find a way to make it send DTMF events ( both received and transmitted ) to the recorder.

When sniffing the network, after pressing some button on the keypad, we see this phone sending a SIP NOTIFY with DTMF data to the Call Manager, a RFC-2833 event to the far-end's RTP stream, but no RFC-2833 event to the recorder's RTP stream.

Is there some configuration we are missing out?? Is this a known bug or limitation??

Thanks in advance

[Karthik Sivaram]

Hi Sergio,

Please check this bug CSCua47105.

Hope this helps!

Thanks,

Karthik

[sergio.castelani]

Hey Karthik!

Phone is working with payload 101 already. We can see it sending RTPs with payload 101 to its far-end side. Only at the recorder call legs (far/near ends) they are not happening.

Here is the sequence of SIP messages within SDP negotiation, from the phone perspective, for the recorder's

near-end leg:

-> INVITE

v=0

o=CiscoSystemsCCM-SIP 4275 1 IN IP4 192.168.2.232

s=SIP Call

c=IN IP4 192.168.2.232

t=0 0

m=audio 4000 RTP/AVP 0

a=label:X-relay-nearend

a=rtpmap:0 PCMU/8000

a=ptime:20

a=inactive

<- 200 OK

v=0

o=Cisco-SIPUA 19606 0 IN IP4 192.168.2.75

s=SIP Call

t=0 0

m=audio 19134 RTP/AVP 0 101

c=IN IP4 192.168.2.75

a=rtpmap:0 PCMU/8000

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-15

a=inactive

-> INVITE (no SDP)

<- 200 OK

v=0

o=Cisco-SIPUA 19606 1 IN IP4 192.168.2.75

s=SIP Call

t=0 0

m=audio 19134 RTP/AVP 0 101

c=IN IP4 192.168.2.75

a=rtpmap:0 PCMU/8000

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-15

a=sendrecv

-> ACK

v=0

o=CiscoSystemsCCM-SIP 4275 2 IN IP4 192.168.2.232

s=SIP Call

c=IN IP4 192.168.2.171

t=0 0

m=audio 40042 RTP/AVP 0 101

a=rtpmap:0 PCMU/8000

a=ptime:20

a=recvonly

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-15