Introduction to VoIP and Asterisk

The Asterisk presentation was initially notable for the absence of the presenter, Julien Goodwin. He eventually turned up, and gave rather a good talk given that it was largely a talk: his laptop just refused to talk to the projector. This is turning into something of a theme: regardless of whether Linux is ready for the desktop, it?d really be nice if it was ready for the conference room by the next time I hit to a conference.

Julien generalised the concept of VoIP to ?Voice over a packet?switched network?, as you can end up with your voice going over other level three?ish protocols (ATM is the typical example; it might even be nice if this was used more as using TCP/IP gives 30% to 50% packet overhead). He also explained that there?s no automatic money saving by virtue of the different switching technique; VoIP won?t automatically save you money.

He then explained most of the issues behind VoIP; much of this is similar to the talk Ewen gave on Monday (see A sysadmin's view of VoIP). He did cover Speex, though ? this is an (allegedly) patent unencumbered codec that?s optimised for encoding speech, from the people who brought you Ogg Vorbis. This gives good quality results, but does tend to eat a lot of CPU.

QoS was also covered. Apparently, this doesn?t work. At all. Ever. Not even a little. If someone says it works, they have more bandwidth than they?re using, and that?s it.

Integration was the focus of the last half of the talk, with Julien discussing VoIP phone issues. Apparently, if you?re setting this up, you want to go SIP ? it?s more supported than anything else, and is simply more likely to work. Some of the SIP phones he showed were very neat ? running off PoE, and including Ethernet switches so you don?t have to re?wire your office. The integration of VoIP into a business as more than just a phone system was very cool too. Many of the VoIP phones available have little LCD displays and ?feature buttons?, which seem to be programmable ? it may prove useful for a call centre to implement the clocking in and out for its employees using the phones themselves.

Wrapping up, Julien demonstrated Asterisk and VoIP, setting up a simple Asterisk server, calling it, and using a SIP phone to call his VoIP voicemail. He also tried to call an audience member on their cellphone, but this didn?t work as well as might be hoped, although I?m quite happy to blame the conferences? rather congested uplink for this. Julien?s giving another Asterisk talk Thursday afternoon that I may have to hit; setting up a PABX for the flat might be geeky cool, and it?s not like my closet server?s exactly overworked.