Linux Networking Cookbook

Chapter 5. Building a VoIP Server with Asterisk

5.0. Introduction

This chapter introduces Asterisk, the Private Branch eXchange (PBX) implemented entirely in software. Asterisk is the hot new darling of the telephony set; it's both a replacement for existing outmoded and overpriced PBX systems, and it's a doorway to the future. Our current telephone system (at least in the U.S.) is excellent because it's pretty much the same technology invented by Mr. Bell. It has been extensively refined over the years, but hasn't seen much in the way of invention.We won't see videophones, video conferencing, or integration with all manner of software and portable devices on the old-fashioned public switched telephone network (PSTN). That's coming with Voice-over-Internet-Protocol (VoIP), packet-switched networks, and broadband Internet.

Asterisk is a PBX and a powerful IP telephony server. Asterisk supports multiple telephony protocols (including SIP, IAX, and H.323), integrates the PSTN with VoIP, and allows you to mix-and-match services and devices (analog, digital, wired, wireless, IP). You may use it as little more than a glorified answering machine, or as a local PBX that is integrated with your existing telephone service, or as part of a wide-area IP telephone network that spans continents. Anywhere the Internet goes, Asterisk goes.

This chapter covers installing and configuring Asterisk 1.4. We'll set up basic business PBX functions: voicemail, a digital receptionist, Internet call services, ...