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H.323 Dial Peers And SIP Dial Peers

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

sip-h323--2016-03-06 19_31_38

sip-h323--2016-03-06 19_31_33

The call succeeds and it is a H.323 call:
sip-h323--2016-03-06 19_33_55

sip-h323--2016-03-06 19_34_40

case#2: one outbound call leg is SIP and the remote inbound call leg is H.323

sip-h323--2016-03-06 19_38_17

sip-h323--2016-03-06 19_38_12

The call succeeds and it is a SIP call:

sip-h323--2016-03-06 19_38_32

sip-h323--2016-03-06 19_38_48

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:

h323-sip--2016-06-13 16_02_02


DTMF Relay

Configuring DTMF support occurs at the voip dial peer level.

Let’s choose which dial peer we will configure DTMF support for.

h323-sip--2016-03-10 19_57_36

We examine if any DTMF settings exist already:

h323-sip--2016-03-10 19_57_461

Line 390 says DTMF Relay is disabled. We configure it under the dial peer:

h323-sip--2016-03-10 19_59_06

and we check again with “show dial-peer” command:

h323-sip--2016-03-10 19_59_411

h323-sip--2016-03-10 20_00_04

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.

h323-sip-dtmf-relay--2016-03-13 11_19_42

h323-sip-dtmf-relay--2016-03-13 11_20_51

We make the call and observe the negotiated DTMF relay method with the command “show sip-ua calls”.

h323-sip-dtmf-relay--2016-03-13 11_26_55

Since there is no custom DTMF relay method, both routers fall to inband-voice DTMF relay:

h323-sip-dtmf-relay--2016-03-13 11_28_23 h323-sip-dtmf-relay--2016-03-13 11_28_09

Let’s change the method to H245 alphanumeric on the UAC:

h323-sip-dtmf-relay--2016-03-13 11_32_31

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.

h323-sip-dtmf-relay--2016-03-13 11_32_52

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 none inband-voice
H245-alphanumeric cisco-rtp h245-signal rtp-nte sip-kpml sip-notify none inband-voice
sip-kpml h245-alphanumeric inband-voice
cisco-rtp h245-alpha inband-voice
cisco-rtp sip-notify inband-voice
sip-notify sip-notify sip-notify
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.



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