An increasing number of companies are taking advantage of Voice over IP (VoIP) technology. Before implementing VoIP, companies must decide if the packetized voice should be delivered over Layer 2 networks such as ATM or Frame Relay, or over Layer 3 IP networks. This comprehensive book presents the latest standards and pradices so you can determine which approach is best for your company. Drawing upon years of pradical experience, the authors explore the unique engineering problems posed by running voice over a connectionless network. They dearly explain the advantages and disadvantages of IP versus traditional packet networks. This book is a significant expansion of the authors'first edition, which published in 1998 and had the distinction of being the first book in the industry dedicated to this important topic of key interest to enterprise customers.