In this article we will play with a couple of dial peer combinations between a source gateway and a destination gateway.
Here is the network setting:
x5002 — Mongi Shop router — PSTN router — x4002
Playing With Dial Peer Session Protocols
case#1: one outbound call leg is H323 and the remote inbound call leg is SIP
The call succeeds and it is a H.323 call:
case#2: one outbound call leg is SIP and the remote inbound call leg is H.323
The call succeeds and it is a SIP call:
So from both cases, we see that the type of session protocol used for outbound call legs follows what is configured on the outbound call leg, despite the difference with the remote inbound call leg.
But, why does the terminating gateway still accepts inbound call legs whether they are H.323 or SIP? That’s because SIP and H.323 services are up on the router.
So to force the router to stop the H.323 service for example, we can do that as follows:
Configuring DTMF support occurs at the voip dial peer level.
Let’s choose which dial peer we will configure DTMF support for.
We examine if any DTMF settings exist already:
Line 390 says DTMF Relay is disabled. We configure it under the dial peer:
and we check again with “show dial-peer” command:
Now we want to examine the negotiated DTMF method between two voice gateways, when a call is established. The network setting is: x5002 — Mongi Shop router — PSTN router — x4002. We call from x5002 to x4002.
- The inbound matched dial peer at PSTN router is voip dial peer 111
- The outbound matched dial peer at Mongi Shop router is voip dial peer 4000
We remove everything related to DTMF relay on both routers.
We make the call and observe the negotiated DTMF relay method with the command “show sip-ua calls”.
Since there is no custom DTMF relay method, both routers fall to inband-voice DTMF relay:
Let’s change the method to H245 alphanumeric on the UAC:
We make the call. The same DTMF method (inband-voice) is agreed upon. That’s because the inbound matched dial peer on the UAS does not support the H245 alphanumeric method.
The following table summarizes what I’ve found from experiencing with different combinations of DTMF relay methods, on the UAC and the UAS.
|UAC DTMF method||UAS DTMF method||negotiated DTMF method|
|H245-alphanumeric cisco-rtp h245-signal rtp-nte sip-kpml sip-notify||none||inband-voice|
|H245-alphanumeric cisco-rtp h245-signal rtp-nte sip-kpml sip-notify||sip-notify||sip-notify|
Notice that, in the absence of a common DTMF method between the UAC and the UAS, both fall to the default which is Inband-voice.