TABLE OF CONTENTS Softswitch is a product driven by the need to incorporate intelligence into Voice over Internet Protocol (VoIP) networks, interface IP networks, and the Public Switched Telephone Network (PSTN) and to coordinate features across networks. As outlined in the previous chapter, the first applications of softswitch were the gatekeepers (aka gateway controllers) that were incorporated in networks of VoIP gateways. In order to better understand a softswitched network, it is necessary to dissect VoIP down to the protocol level. Many volumes on VoIP can be found on the book market, and this book will not attempt to cover it in detail. The importance of VoIP protocols relative to softswitch is that they are the building blocks that make VoIP possible.
In November 1988, Republic Telcom (yes, one "e") of Boulder, Colorado, received patent number 4,782,485 for a "Multiplexed Digital Packet Telephone System." The plaque from the Patent and Trademark Office describes it as follows: "A method for communicating speech signals from a first location to a second location over a digital communication medium comprising the steps of: providing a speech signal of predetermined bandwidth in analog signal format at said first location; periodically sampling said speech signal at a predetermined sampling rate to provide a succession of analog signal samples; representing said analog signal samples in a digital format thereby providing a succession of binary digital samples; dividing said succession of binary digital samples into groups of binary digital samples arranged in a temporal sequence;
