Saturday, April 25, 2009

Normalizing inbound calls and solving the "9" prefix dilemma

I don't believe it is actually written anywhere but I've found out recently that the location profile you specify on your mediation server is actually used for normalizing inbound calls. Seems straightforward but it isn't always clear what these options and settings are used for.

This post is designed to bring awareness to this process first of all but more importantly I talk about the dilemma of including normalization rules for "9" prefix calling.

First off, if you're performing digit manipulation in the gateway for inbound calls you're probably doing the work of OCS anyway. Remove any digit manipulation you have in the voice gateway (or equivalent, i.e. Call Manager).

You want to create a normalization rule and include the name of the mediation server in it so you can easily keep track of which location profile is for what server. For example, if your mediation server is called "abedmocsm01" then create a LP called "abedmocsm01.domain.com".

Include the most common rule for North America calling as follows:

^(\d{10})$ which translates to +1$1

Follow suit by adding rules for your DID's and non-DID ranges. If you have a main number with non-DID's behind it then it would look something like:

^5(\d{3})$ which translates to +17805551212;ext=5$1

Now that you have that sorted, you'll notice that you don't have a rule for something like:

^9780(\d{7})$ which translates to +1780$1

The above rule wouldn't apply since the PSTN (or PBX) would never send a 9, then digits. Using this "split Location Profile" type scenario allows you to get away with not having both of these rules:

^9780(\d{7})$
^780(\d{7})$

I hope his is some value to those out there.

Cheers,

Jason

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