Chapter 3. Call Routing with Asterisk

In the last two chapters, we have looked at some advanced dialplan techniques, and the means of ensuring that your customer's IP network is VoIP-ready. Spending time and effort on this, however, is wasted if you do not consider what happens once the call traffic leaves the customer's network. Unless you are routing calls within the LAN or WAN, normally meaning internal calls or inter-office calls, the call will be required to leave your control and pass to a service provider. This needs careful consideration up front as which type of service you use, and when, will affect the cost and quality of each call.

Using an IP-capable telephone system opens up a raft of call routing possibilities that can easily appear quite bewildering, even to someone who has already implemented an Asterisk-based system. However, by breaking your requirements down into bite-sized chunks it is possible to navigate this potential minefield and ensure you are routing all your calls effectively. This chapter explains the options available for call routing, and suggests some techniques that can be used to improve the performance of your Asterisk system, both in terms of cost efficiency and call quality.