Network Infrastructure and Architecture: Designing High-Availability Networks

9

PHYSICAL CIRCUIT SWITCHING

9.1 Introduction

9.2 Switching and Why It Is Important

9.3 Three Types of Switching

9.3.1 Switching of Physical Circuits

9.3.2 Switching of Time-Division-Multiplexed Signals

9.3.3 Switching of Cells and/or Packets

9.4 Quality of Service

9.5 Special Services

9.6 Switching in One or More Stages

9.7 Cost Model for Switch Implementations

9.8 Crossbar Switch Concept

9.9 Optical Crossbar Switches

9.10 Digital Electronic Crossbar Switches

9.10.1 Control of Digital Crossbar Switches

9.10.2 Cost Model for Digital Electronic Crossbar Switches

9.10.3 Growth Limits of Digital Electronic Crossbar Switches

9.10.4 Commercial Examples of Electronic Crossbar Switches

9.11 Multistage Crossbar-Based Switches

9.11.1 Routing and Blocking in Clos Networks

9.11.2 Multicast in Clos Networks

9.11.3 Implementation Costs of Clos Networks

9.12 Desirability of Single-Stage Fabrics and Limits to Multistage Fabrics

Key Points

References

9.1 INTRODUCTION

This chapter has two primary goals: (1) to divide the world of switching architectures into three classes: switches for physical circuits, switches for time-division-multiplexed signals, and switches for cells and packets, and (2) to describe in some detail the architectures of the first class of switches, the physical circuit switches. We shall see that physical circuit switches fall into two categories: (1) single-stage switches and (2) multistage switches. The conceptual simplicity and beauty of single-stage crossbar switches are ...