ABSTRACT

Link State Routing (LSR) is a routing approach where each router maintains a complete view of the network, i.e. where each router knows the complete network topology and the correspondence between available prefixes and network elements. This chapter addresses the principles of LSR, i.e. the fundamental mechanisms and data structures that always must be present in LSR protocols, irrespective of the technology implementing them. It discusses the various aspects concerning the representation of the routing information and the synchronization mechanisms. The chapter introduces the Hello protocol, examines the structure of the Link State Database (LSDB), and explains how the forwarding tables are built from the LSDB. It also addresses the mechanisms used to disseminate the routing information throughout the network, including the reliable flooding procedure. The chapter describes the initial LSDB synchronization process. It provides a summary of the control messages that support the various synchronization mechanisms.