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DTMF transmission on DMA

Pankaj Malhotra
Occasional Contributor

DTMF transmission on DMA

Hi,

 

This is the call flow:

 

Ip phone---> CUCM----SIP trunk------> DMA-----H323----> RMX

 

DTMF does not work when trying to enter conference room after connecting to RMX.

 

CUCM does not get DTMF events in 200 ok from  DMA so, CUCM picks up RFC2833 ( default on SIP) and sends RTP-NTE to RMX directly.

But since RMX is an H323 EP on DMA, it is incapable of supporting RFC2833. Is DMA not capable of sending what DTMF it will negotiate so that CUCM can send SIP KPML to DMA and DMA can further send OOB h245 DTMF to RMX?

 

Are there any known issues on supplementary services as well when trying to transfer , hold a call from IP phone connected to RMX ?

 

Is there any releavant document to add DMA as H323 endpoint on CUCM so that end to end call flow becomes H323 and issues becuase of protocol interoperability can be avaoided?

 

Regards,

 

Pankaj

Message 1 of 5
4 REPLIES 4
Bazzuck
Respected Contributor

Re: DTMF transmission on DMA

Hi Pankaj

 

"In H.323, DTMF tones are usually sent over the H.323 signaling path. In SIP, DTMF tones are usually sent over the media path as a special RTP payload packet (see RFC 4733). Because of this difference and because the DMA system isn’t in the
media path, its gateway function doesn’t support DTMF transmission."


from >DMA® 7000 System Operations Guide 6.0< page's 264

 

There is a guide >Polycom Unified Communications Deployment Guide for Cisco Environments<, which can help you design your network.

 

You can't add DMA to CUCM as a H323 endpoint\gateway.

 

I suggest to use one of the following designs:

  1. Ip phone---> CUCM----SIP trunk------> DMA-----SIP----> RMX
  2. Ip phone---> CUCM----SIP----->Cisco VCS Control------H323----> DMA-----H323----> RMX (if you would like use H323 for RMX)
  3. Ip phone---> CUCM----H323------>Cisco IOS Gatekeeper-----H323------> DMA-----H323----> RMX (again H323 for RMX, I think it is officially unsupported solution, but it works fine)

 

Regards

 

 

Message 2 of 5
Pankaj Malhotra
Occasional Contributor

Re: DTMF transmission on DMA

First, Regarding DTMF transmission, CUCM chooses to send DTMF in RTP-NTE events along with RTP stream only because DMA never exchanges it's peers capabilities. If DMA would have informed CUCM on what was supported by H323 RMX, then CUCM would have sent KPML OOB in SIP signalling and DMA should have converted it to H245-alphanumeric OOB DTMF for RMX. CUCM chose to send RFC2833 only on best efforts as DMA did not exchange allow events field or nofity method event in 200 OK SIP message.

 

Second, in regards to making the entire call flow H323. Can we add DMA as an H323 client on CUCM or add H323 gateway on CUCM? We don't have IOS gatkeeper in the setup.

 

Message 3 of 5
Pankaj Malhotra
Occasional Contributor

Re: DTMF transmission on DMA

Sorry you already replied to endpoint/gateway addition part.

Message 4 of 5
Bazzuck
Respected Contributor

Re: DTMF transmission on DMA

You can try to use VMRs on the DMA. In this case, if DMA recieve a SIP call to VMR from CUCM, DMA will create a conference on RMX and send a SIP call to RMX and DTMF should works.

Message 5 of 5