Optimization of Computer Networks

Chapter 4Routing Problems

4.1 Introduction

Routing in communication networks is the particular set of rules that decide the path followed by the traffic units from their origin to destination nodes. The two main technological strategies to forward the traffic are flow-based routing and destination-based routing:

• In flow-based routing, network nodes are able to identify the demand of the arriving traffic and make a different per-demand routing decision. Flow-based routing is characteristic of connection-oriented technologies like MPLS, ATM, frame-relay or SONET/SDH, where a flow completes a connection establishment stage before any data is carried. During this stage, the network decides and signals the flow route and configures the internalrouting tables of the traversed nodes accordingly. After that, the flow data frames are attached enough control information in their headers so that the intermediate nodes can enforce the routing previously defined.
• In destination-based routing, the network nodes apply the same routing decision to all the traffic units targeted to the same destination. This happens irrespective of the particular flow or demand the traffic belongs to or, for instance, the particular initial node of the traffic. IP and Ethernet networks are the main representatives of destination-based routing, as IP routers and Ethernet switches make forwarding decisions observing ...