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MPLS Traffic Engineering

MPLS traffic engineering (TE) is the ability to establish LSPs according to particular criteria (constraints) in order to meet specific traffic requirements rather than relying on the path chosen by the conventional IGP. The constraint-based IGP examines the available network resources and calculates the shortest path for a particular tunnel that has the resources required by that tunnel. Traffic engineering enables you to make the best use of your network resources by reducing overuse and underuse of certain links.

Constraint-based routing (CR) makes traffic engineering possible by considering resource requirements and resource availability rather than merely the shortest path calculations. Constraints are determined at the edge of the network and include criteria such as required values for bandwidth or required explicit paths. You can use RSVP-TE as the label distribution protocol for traffic engineering. The IGP propagates resource information throughout its network. RSVP-TE employs downstream-on-demand, ordered control for label mapping and distribution.

Explicit routing specifies a list or group of nodes (hops) that must be used in setting up the tunnels. CR explicit paths can be strict or loose. Strict paths specify an exact physical path, including every physical node. Loose paths include hops that have local flexibility; the hop can be a traditional interface, an autonomous system, or an LSP.

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