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PDD (Post Dial Delay) and trunks SIP


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My phone is a GS 2130 and I'm trying to call out. My trunk sometimes takes up to 4-6 seconds to receive back the 180 or 183 from provider. I would like to somehow send a SIP 180 Ringing to the phone right away. The customer is complaining that the Post Dial Delay is too long, and it frustrates him. I tried in the trunk settings to change to different options on Ringback on incoming calls, ocal ringback generation for outbound calls and PRACK support, but it does not help.

I want phone to ring right away, does not matter if it receives the 183 or 180 from the trunk. How can i forcet this?

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Well first of all, if the provider does not provide the ringback thats for a reason — the called phone does not ring yet! Especially when calling cell phones it really can take some time before the phone actually alerts the user. To bridge that time, we provide "comfort" noise so that the line does not sound dead. When calling the mobile app we provide a special ding-dong ringtone to bridge the sometimes awful long time before the app wakes up. 

What you can try on the trunk is to change the "Local ringback generation for outbound calls" setting. If the provider sends any kind of 18x that could solve the problem. The other "hack" would be to load a new audio_moh/noise.wav file that provides some kind of ringback tone, similar to what is happening when calling the app. 

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The problem with 18x without media is that it's not possible to control how the ringback sounds (e.g. country) and it also adds additional delay upon pickup for connecting the call. Because of that the PBX always uses 18x with SDP and provides media, either locally from the PBX or from the trunk.

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