The following is a brief of John's presentation, January, 2007:
Monday 22nd of January, http://www.cambridgelug.org/
VOIP
Linux & Asterisk
Completely VOIP (In and Out) at Net Direct
Introduction to VOIP and SOHO
VOIP Definition
Voice over Internet Protocol
suite of protocols (use Intenet protocols: SIP, RTP, IAX, H.323, MGCP, and more)
Call setup and session signaling protocols
Audio/Video protocols
Market supports SIP (Session Initiation Protocol)
Why use VOIP
Cheap
$2.50/phone number, 1.1cent to 2 cent/minute calls
Flat rate - $40/month unlimited NA calling