We are planning to change the PSTN connection from ISDN to SIP.
We have the following equipments:
CP7941 (with SCCP)
Cisco2851 as IOS voice gateway (C2800NM-SPSERVICESK9-M), Version 12.4(22)T)
The current call process is the following:
7941 -SCCP-> CUCM -H.323-> Cisco2851 -ISDN-> Telco
We do not have any problem via ISDN. The ringback tone from Cisco2851 to 7941 goes in audio mode (in RTP).
The planned and tested call process is the following:
7941 -SCCP-> CUCM -H.323-> Cisco2851 -SIP -> Telco
We found that no Ringback tone on the IP phone while calling to PSTN via SIP provider but the phone displayed âRing outâ message.
We make several debugs, and we saw that Telco sent us âSIP/2.0 180 Ringingâ and Cisco2851 sent âALERTINGâ to CUCM while was not âRingback toneâ on calling phone.
What special setting is necessary to get âRingback toneâ on IP phone if the SIP provider sends Ringing message?
Is there any possibility to make IP Phone to generate âRingback toneâ?
You can try two things:
This service parameter:
Use H225 User Info: Use ANN for Ringback
You will want to make sure your H323 gateway has a ANN in the MRGL as well. This will cause CUCM to generate ringback locally.
Or on the H323 gateway:
You can add an MTP in the MRGL
Click 'MTP Required'
Click 'Enable Inbound Fast Start'
Click 'Enable Outbound Fast Start'
This will cause the CUCM to send outbound fast start, which will translate into SIP early media. Then, we should get a 183 Session Progress back instead, and we'll cut through the audio from the provider.
I have tried your first suggestion (the service parameter changed to âUse ANN for Ringbackâ and set on the H323 gateway the MRGL with ANN and restart CallManager) but I did not hear the Ringback tone.
Your second suggestion was working: I have heard the Ringback tone. This solution has a side effect: All conversation traffic (voice RTP) went through the CallManager not only at the tone generation. I think it was because of MTP. (By the way we have got same â180 Ringingâ signal from the provider but they have sent the Ringback tone.)
I do not want to load the CallManager with conversational traffic. How can I prevent the conversational traffic goes through CallManager? Can I set the SIP settings in the IOS gateway in order to make provider to send Ringback tone?
This isn't something we can control from the gateway.
What you can try doing is putting the MTP on CUBE by configuring an MTP software resource. That way calls out your CUBE use your CUBE as an MTP and voice doesn't go through CUCM.
It seems good. But I have a little problem with it:
We have more sites. We use G.711 at the central site and G.729 from remote sites. If we use MTP then we limit the codec type to one (G.711 or G.729). We would like to use to the provider direction both types of codec.
Is there any solution to this? CUBE is able to service two MTPs? Can I set in CallManager two logical gateways which are same hardware?
Thanks for help,
Rather than have two gateways, can you not defined two MTPs on the CUBE, one for G.711 and one for G.729?
I have thought that the solution to my problem would be the setting two MTPs and two H.323 gateways.
Two gateways are necessary because I can assign a codec to one gateway; therefore I need another gateway for assigning another codec.
I think that I can define two MTPs in the CUBE, because I see the possibility to bind separate interface to the âsccp ccm groupâ.
How can I set the IOS gateway that the CallManager could see it as two H.323 gateway?
Thank you for help,
You could configure a secondary IP address on the interface, but you may have mixed results if you need to use a H323 bind command.
Otherwise, CUCM refers to the gateway by the IP address and CUBE is not going to switch IP addresses for incoming calls.
You may want to look into why you need an MTP for this call. Make sure the ANN is available, and that the region between the ANN and the CUBE doesn't need a transcoder.
You are right. This way becomes complicate.
I have gone back to starting stage and I have got solution.
I have set at the CUBE this:
After changing the setting in CUBE, I get Ringback tone on IP phone during calling to PSTN via SIP.
The cause of the problem was the following:
The provider sent â180 response with SDPâ without RTP media. The gateway thought from â180 response with SDPâ that RTP media would be arriving and opened media path on H.323 side with CallManager. We could not get ringback tone on the IP phone, because the phone had opened the media path to CUBE.
This is the reference, when the SIP gateway makes early media cut-through or local ringback.
Thank you for the suggestions and help,
On 13th February I could resolve my problem. How can I mark this conversation that it resolved my problem?
Is there any possibility to mark the conversation that resolved the problem by the opener participant?
Next to the replies there should be an option to check that 'this solved my problem'. I wish I could tell you more, but I haven't posted a question :)
It should be somewhere on the post, because I have seen threads with multiple posts that 'resolve the issue'.