10.1. Introduction

Today, routing a connection in a traditional optical transport network involves a number of steps. Many of these involve manual actions, and hence painstaking and error-prone. Also, the routing infrastructure is predominantly centralized. A centralized Element or Network Management System (EMS/NMS) acts as the repository of the network topology database. The entries in the topology database are often entered and updated manually. Routers are computed automatically, but with manual intervention. There is a strong desire among the network operators to transition from this centralized and manual approach to a more distributed and automated routing system. In this chapter, we discuss a distributed routing architecture for optical networks that has been endorsed by different standard bodies, as well as user communities.

The primary focus of this chapter is on intradomain routing. Interdomain routing is the subject of Chapter 12. Also the emphasis in this chapter is on protocols for network topology discovery and dissemination. The path computation aspect of routing is covered in Chapter 11. Much of the discussion in this chapter is based on the work in the Internet Engineering Task Force (IETF), the International Telecommunications Union (ITU-T), and the Optical Interworking Forum (OIF). These proposals are generally extensions of intradomain IP routing protocols, such as OSPF and IS-IS, to handle routing of connections in optical networks.