Modeling and Simulation of Complex Communication Networks by 
Building Telephony Systems with OpenSIPS - Second Edition by 
Voice Over Internet Protocol (VoIP)
Voice over Internet Protocol, also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet.
Voice Over Internet Protocol (VoIP)
Information about VOIPs from the Federal Communications Commission
article from Howstuffworks.com
online copy of book
How Does VoIP Work? The Beginner's Guide to VoIP Phone Systems
Nextiva Blog
Phone and computer connection diagrams
online diagrams and information
Cisco. What is Voice over IP? How is it different from unified communications? And how can it help your small business?
Understanding Voice over Internet Protocol (VoIP) by MATTHEW DESANTIS
pdf document on VOIP from US-CERT
Information on VOIP installation, issues, and troubleshooting
link to online book
Carrier Grade Voice over IP, Third Edition by 
VoIP Technologies by 
Hacking Exposed Unified Communications & VoIP Security Secrets & Solutions, Second Edition by 
Voip 63 Success Secrets - 63 Most Asked Questions on Voip - What You Need to Know by 
Cisco a Beginner's Guide, Fifth Edition by 