Chapter 1. Introduction

Digital network connectivity is dependent upon the availability of a reliable synchronization source to provide a timing reference to the network elements. This fifth edition of this booklet is a revised and extended version of Issue 4, published March 1997, reissued to incorporate the new Larus STS 5800 system and to remove information pertaining to the STS 5300 system. This issue also reviews recent changes to standards, and addresses new technology. The booklet discusses the hierarchical clocking scheme, and its applications within public and private networks. Networks that use asynchronous digital multiplexers, networks that use synchronous multiplexers (SONET), and networks that mix the two technologies, are discussed.