The authors do a great service for readers by breaking packet telephony into its component technologies and explaining each carefully. Coverage of the various protocols that enable voice over IP, particularly H.323 and Session Initiation Protocol (SIP), is simultaneously clear and deep. The same goes for media gateway protocols and various schemes for translating sounds into digital signals and back again, while retaining maximum clarity. There is even some practical material: concluding chapters diagram Cisco router configurations for voice traffic, and flesh out solutions with case studies.

You will like this book if you need to implement a voice over IP system and know more about IP than you do about traditional voice telecommunications. The authors' patient and detailed explanations of traditional telephony concepts and voice over IP protocols will mesh nicely with your existing data communications knowledge, enabling you to make wise design and product decisions. --David Wall, amazon.com

Topics covered: The Public Switched Telephone Network (PSTN), signaling specifications (including Bell System, ISDN, and Signaling System 7), the basics of Internet Protocol (IP), modulation and compression of voice, Quality of Service (QoS), H.323, Session Initiation Protocol (SIP), and gateway protocols. Business considerations of Internet telephony also get coverage.