Monday, July 23, 2007

OSCON: Understanding Asterisk

My afternoon tutorial today is Understanding Asterisk given by Brian Capouch. I went to Brian Acker's session on Hacking your Home Phone during OSCON 2005 so, like this morning, I thought that it was worth following up with a tutorial.


Brian Capouch talking about Understanding Asterisk

Update: Brian's gone back to basics and is talking about how the POTS network actually operates, and I'm suddenly realising why VoIP is taking off so much more quickly in the US than it is back home in the UK. I was totally floored to find out that some US telcos charge for touch tone dialling. That's just bizarre...

Update: He's going through the two different views of how this stuff works, it looks like the telephone guys and the computer guys really didn't talk things out before setting up standards and writing software. Both sides call the same things different names.

Update: Brian is giving a good impression of someone trying to cram a ten week lecture course in a three hour tutorial. He's got a lot of background material here, and I'm not sure its really relevant. For instance do you really have to talk about the Nyquist frequency and the nuts and bolts of analog-to-digital conversion to talk about configuring and using Asterisk? In fact he hasn't mentioned Asterisk much at all yet, this isn't really what I'd signed up...

Update: Coming from an academic background it's really very apparent that this guy is an academic, Brian is obviously really excited by the mathematics behind VoIP and about the theory behind different types of codecs.
Codecs are really interesting... part of the fun of running an Asterisk system is playing with codecs. - Brian Capouch
I'm not sure he's really pitching this material at the right people, at a different time and place I'd be quite interested, but I'm not sure he's carrying the audience. I'd be more interested in a hands-on look at Asterisk itself. I wasn't looking to have fun with different codecs, I was looking for some practical look at how to set up a VoIP network and interconnect the system with other providers. Hopefully we're going to get onto some more practical stuff later on...

Update: Googling for slightly more practical stuff, it looks like O'Reilly book "Asterisk: The Future of Telephony" by Meggelen, Smith & Madsen is available online under the Creative Commons License.

Update: Time for afternoon coffee, back after these messages...

Update: Back from the break, and Brian has actually started to talk about Asterisk. This material basically looks like what I was expecting him to kick off with a couple of hours ago. He's doing a demo right now, although I'm not sure how useful it's going to be as the demo seems consist of him going through how his own home network is set up.

Update: After staring at a directory listing of the Asterisk source code for a bit, we're looking at some random configuration files. I don't think this is a particularly useful approach, I don't even know which file we're looking at here, what it's for or why I'd like to edit it. I especially don't know at what stage of an install I'd be editing it...

Update: I'm sure some people in the room are following this, but I'm not. Brian is standing at the front of the room with multiple SIP devices, calling each other, while we're watching the logs from his home Asterisk server.

Update: ...and we're done. To be perfectly honest I don't think I know anything more about Asterisk than I did three hours ago, however at least I am leaving with the determination to buy the books I was hoping to avoid buying by going to this tutorial in the first place.