Chapter 13. Networks in Switch Fabrics

A switch fabric is the core switching engine in switching devices as routers. Chapter 3 presented an overview of switching devices. This chapter analyzes this core segment of such devices and introduces several topologies for switching networks.

This chapter explores the following topics:

Characteristics and features of switch fabrics
Crossbar switch fabrics
Blocking switch fabrics
Nonblocking switch fabrics
Concentration and expansion switches
Shared-memory switch fabrics
Techniques for improving performance
Case study multipath buffered crossbar

We begin by classifying characteristics of switching networks and presenting features and definitions of switch fabrics. Crossbar switches are the building blocks of switching fabrics, so all aspects of this switch are covered. The case study at the end of this chapter combines several buffered crosspoints to form a buffered crossbar. Blocking switches are constructed with crossbar switches, including Omega networks , Banyan networks , Delta networks and Bene networks . Nonblocking switches constructed with crossbars include Clos networks . Concentration-based and expansion-based switching networkstwo special-purpose switch fabricsare investigated as well.

A quite different approach for switching in time domain uses shared memory, without using any switch elements. Switch fabric techniques that offer better performance include the use of buffering, combined networks, and parallel-plane switching networks.