One of the many advantages of IP telephony is having client-server type applications, which allow us to enable remote extensions registered to our PBX. We can therefore integrate an enterprise's main office and its branches into one entity or a huge intersite PBX with the possibility for offering all the main services (voicemail, DID routing, caller ID, conference bridge, and so on.) to all the users across a city, a nation, or even across many countries.

This possibility may also be reached, thanks to the increase in the bandwidth the telecommunication companies are offering recently. Elastix recommends at least a 4 MB ADSL connection to work properly, although its reliability depends on the codec used for each user. Years ago, this only could be achieved by calling through the PSTN by using the DISA concept, with the resulting costs.

Enabling remote extensions helps companies to reduce their telephony costs. We can even register remote users by using a softphone...