asterisk intro

SIP = almost universal VOIP protocol IAX2 (don’t use it!) Codec used to transfer voice-to-data is ULAW

Channels = how many translations from voice-to-data you need to handle. Generally about 1 channel unless you have scaling issues.

Registration = how your box is registered to accept calls for a particular number

Asterisk can do:

  • conference calls.
  • caller ID
  • special prompts
  • voice mail
  • asterisk-to-asterisk can be free because there is no middle parties
  • telemarketer torture

AEL = Asterisk Extension language

A C-like language used to configure the behavior of an asterisk installation


  • People can hack into your box and call Siberia.
  • SIPVicious is a tool originally written to check for hacks against Asterisk but is used to hack.
  • Can it be placed in the cloud or do we need a datacenter?
  • The internet goes down
  • 64k bandwidth each way
  • Echos are troublesome (Open Source Echo Canceller)
  • Huge amounts of servers to run this thing

Changes in install screen

  • include the sounds in the codec (last three items)


  • check asterisk hosting


  • O’Reilly book: Asterisk: The future of telephony