MPLS: traffic engineering and security applications

The growth in access speeds and the convergence of so-called "triple play" services (Internet, voice/visioconferencing, TV/video-on-demand) on a unifying IP (Internet Protocol) infrastructure are leading to a considerable increase in IP traffic volumes, as well as new constraints in terms of quality of service (QoS) and availability (dependability) for IP networks.

Traffic engineering, QoS and security mechanisms are required to support this evolution in the volume and nature of traffic transported. Traffic engineering brings together all the routing control methods used to optimize resource utilization, while guaranteeing quality of service (bandwidth, delay, etc.). The aim of traffic engineering mechanisms is to maximize the amount of traffic that can pass through a network, in order to delay investment as far as possible, while maintaining quality of service. Various traffic engineering methods for IP networks have been specified for several years. One of these is based on the use of MPLS (Multi Protocol Label Switching) technology. MPLS technology is particularly well suited to traffic engineering, as it allows the creation of explicitly routed paths, independently of the IP route (which is based on a shorter path to the destination). This makes it possible to use alternative paths to the IP path, enabling better load distribution in the network and more efficient congestion management.

The application of MPLS to traffic engineering is called MPLS Traffic Engineering (MPLS-TE). MPLS-TE enables the establishment of MPLS tunnels, explicitly routed according to the constraints of the traffic transported (bandwidth, delay, etc.) and the resources available in the network. These MPLS-TE tunnels can be likened to connections. MPLS-TE thus creates a connected mode in IP networks, optimizing the use of resources and maximizing the traffic load that can circulate on the network, while preserving quality of service (congestion management). MPLS-TE constraint routing requires a set of routing and signaling protocols and algorithms.

To ensure good availability of IP networks and meet the high security requirements of real-time services (voice, videoconferencing), it has also become essential to have rapid rerouting mechanisms in the event of link and node failures. MPLS-TE technology meets these security requirements. The MPLS-TE Fast Reroute mechanism consists in protecting primary tunnels with pre-established backup tunnels. In the event of failure of a network element (link or node), traffic from a primary tunnel is rapidly switched to a backup tunnel in less than 100 ms.

This dossier presents the fundamental concepts of MPLS-TE technology. The first part describes the concepts and mechanisms involved...