Table of Contents:

Definition and Overview

1. Transport Network Role

2. Multiplexing

3. Asynchronous Hierarchy: Comparison with SONET

4. Types of Network Elements

5. SONET Hierarchy

6. Structure to Carry Data

7. SONET Network Architecture

8. When Is a Separate SONET Layer Needed?

Self-Test

Glossary

PDF of this tutorial

Definition
Synchronous optical network (SONET) offers cost-effective transport both in the access area and core of the network. For instance, telephone or data switches rely on SONET transport for interconnection.

The optical layer provides the foundation of transport services for both metro and long-haul applications. It also directly supports data services. The optical layer is now evolving to provide the same level of sophistication that has been achieved with synchronous transmission, such as performance monitoring and network resilience (i.e., the ability to recover quickly from a link being cut). Thus, the SONET layer will remain for some time. Figure 1 illustrates the access, switching, packet multiservice, SONET, and optical layers in the telecommunications network.

Figure 1. Telecom Network Overview

Overview
The objective of this tutorial is to clarify what SONET is, what it does, and what benefits it offers.