ISPs must deploy a physical topology that meets customer needs, while provisioning multiple circuits of varying bandwidths. After deploying the network, ISPs then have to map customer traffic flows onto this new physical topology.
Traffic engineering provides one answer.
It enables an ISP to maximise operational efficiency and minimise operational costs. In so doing, it can offer more options, lower costs, and provide better service to its customers. This approach is becoming ever more valuable as ISP networks grow larger and as customer demands become greater. IGP extensions can contribute to network congestion because bandwidth availability and traffic characteristics are not taken into account when forwarding tables are built. Traffic engineering resolves this issue by providing ISPs with precise control over traffic flows within their routed domains, thereby letting them redirect traffic away from the shortest path and onto a potentially less congested route.