K-12 School Computer Networking/Chapter 4
YouTube Video on Voice over IP: Shenetta Richardson, Systems Engineer 
The future of real time voice communications is evolving from the traditional TDM circuit switch infrastructure. VoIP is simply the transmission of voice traffic over IP-base networks. The Internet Protcol was originally designed for data networking. The success of IP is becoming a world standard for data networking and has led to adaptation into the voice network which allows you to make voice calls using a broadband internet connection instead of the regular analog phone line.