http://www.asterisk.org/sites/asterisk/files/mce_files/documents/asterisk_quick_start_guide.pdf

What is Asterisk? Asterisk is an open source framework for building communications applications. Asterisk turns an ordinary computer into a communications server. Asterisk powers IP PBX systems, VoIP gateways, conference servers and more. It is used by small businesses, large businesses, call centers, carriers and governments worldwide. Asterisk is free and open source. Asterisk is sponsored by Digium, the Asterisk Company. Asterisk is “under the hood” in countless voice communications applications and is capable of interfacing with many traditional Telcom protocols, VoIP protocols, and codecs. Asterisk provides a staggering list of capabilities and features including: IVR ACD Audio and Video Conferencing Voicemail Call Recording Fax termination CDR About this Quick Start Guide This guide provides step-by-step instructions for compiling and installing Asterisk. Also included are basic instructions on controlling Asterisk via its Command Line Interface, or CLI. Sample Asterisk configuration and SIP soft-phone configuration will also be presented. This will culminate in your ability to dial over the internet using the IAX2 protocol to Digium. For further reading, a wealth of resources including information on Commercial Support provided by Digium, The Asterisk Company can be found at: http://www.asterisk.org/support NOTE: Any server accessible from the public Internet should be security hardened, and an Asterisk is no exception. General security best practices are not within the scope of this Quick Start Guide; however you may see Table 2 for default IP ports utilized by Asterisk. Instructions are provided for the Long Term Support (LTS) version of Asterisk, which is currently 1.8.