Chapter 8. Traffic Engineering

Traffic engineering is a familiar topic in the communications industry. Network operators have used traffic engineering on circuit infrastructure to evenly distribute traffic in the network. In ATM networks, PVCs are placed by operators such that network load is distributed evenly. Even dynamic routing protocols such as Private Network to Network Interface (PNNI) send topology and bandwidth information to the switches, and switches perform admission control when admitting virtual circuits (VC) in the network.

Today most networks are packet-networks, so they also use mesh connections for better redundancy and resilience. If failure occurs, reconvergence causes the IP routing devices to use the new paths in the network. How the new path is calculated is determined by several factors, one of which is link metrics. To perform traffic engineering in an IP network, these link metrics must be manipulated to influence traffic flows. MPLS provides a much needed solution to balance the traffic in the network by building label-switched paths (LSP) and allowing operators to map traffic onto these paths. This chapter describes the IP routing problem and shows how MPLS traffic engineering helps solve that problem. It also investigates the applications of MPLS traffic engineering, where it is used, and how it can help in building a protection solution for better network resiliency. One of the first applications of MPLS was to deliver traffic engineering in an IP network.

This chapter discusses this problem statement: Why is traffic engineering (TE) needed in an IP network? We then provide a technical overview of how MPLS traffic engineering can help address the network congestion by using the nonshortest paths. We examine a main application of MPLS TE for protection and restoration, known as MPLS fast reroute (FRR). You'll also see examples of how MPLS TE is used in networks today to address specific problems, such as IP bandwidth guarantee. The management elements of MPLS and TE are dealt with in the Operation, Administration, and Maintenance (OAM) chapter, Chapter 12, "Network Management and Provisioning."