oozenoz

You're definitely on the right set of tracks, just be cautious when making a final decision about your dialing plan and scope... there are some pitfals and things you need to sort out before you begin programming - what you are describing is very easy when there is only one trunk path, you will potentially have several for any single site.

Assume that you will have one VoIP trunk path from site A to B, another from site A to C, and one between B and C, and that you continue to have no overlap of extension ranges (adding that would only complicate this discussion unnecessarily).

Let's say you go forward and make all international calling via the format yxxxx where y defines your call as an international, and xxxx is the foreign site extension. Your user at site A wants to call someone at B, how will the system determine which set of IP trunks to go out so that it does not route the call to site C? (ARS can probably do this for you if you use a 2-digit code, where yx are unique to a given site... again this only works if you have no overlaps on extension ranges).

The alternative (which is something I would strongly urge you consider) would be to create a 2-digit trunk access code for each foreign site. So from Milan, let's say you dial 11 to get to Hong Kong, 12 to get to another site, 13 to another, etc. If you think you are ever going to need more than 10 sets of VoIP trunks at any one site, make the access code 3-digit.

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- calvin