We have been using Asterisk for the last four years; it facilitates our distributed model of operation, effectively bridging the gap between traditional PSTN and VoIP. Asterisk enables us to bring important customer calls into our head office via trustworthy ISDN technology whilst at the same time linking branch offices and remote users via VoIP. If we cannot make an outbound call with our SIP and IAX2 trunks, we simply fall back to ISDN.

Many organisations use Asterisk in conjunction with the Trixbox CE distribution to give an excellent administration front-end with FreePBX and good presence management with Hudlite. FreePBX has a poorly documented feature which allows you to separate devices from users. Therefore as users move through our distributed network, they associate themselves with a device by logging in. Calls can transparently be connected with the user rather than using traditional extensions which do not move. Unfortunately Hudlite does not currently support users and devices, forcing us to stay with device only calls if we wish to retain its features.

 We really did not want to make this choice, we wanted rich presence management, integration with messaging, mobility of users and full logging via a searchable database. We therefore decided to look at Microsoft Office Communications Server (OCS). OCS has come on a long way in the last four years and with OCS 2007 R2 just round the corner and the excellent desktop and PDA client, Communicator 2007, it has a promising future.