Optical Networking Best Practices Handbook

Chapter 11. Optical Packet Switching

Communications technology has seen many advances. Telephony is still here (albeit now mostly digital), but it is apparent that with the advent of the Internet, a large portion of traffic now consists of data rather than voice. Still, the concepts of the "old" telephony world are still in use. In essence, classical telephony is a circuit-switched concept: communication between two parties is realized by establishing a connection, which is reserved for only their use throughout the duration of their conversation. Prior to communication, signaling takes place through the exchange of messages to set up the connection through the various switches on the path between the two parties. This same idea of connection-oriented communications prevails today, and a circuit-switched approach is also taken in so-called backbone networks to provide high-bandwidth interconnections between, for example, telephone private branch exchanges (PBXs). However, in the Internet world, a packet-switched concept dominates. Instead of reserving a certain amount of bandwidth (a circuit) for a certain period of time, data are sent in packets. These packets have a header containing the information necessary for the switching nodes to be able to route them correctly, quite similar to postal services [1].

To provide the bandwidth necessary to fulfill the ever-increasing demand (Internet growth), the copper networks have been upgraded and nowadays to a great extent replaced with ...