Networks Horizon

MPLS Traffic Engineering.

Traffic engineering refers to the process of selecting the paths chosen by data traffic in order to balance the traffic load on the various links, routers, and switches in the network. Traffic engineering is most important in networks where multiple parallel or alternate paths are available.

A major goal of Internet Traffic Engineering is to facilitate efficient and reliable network operations while simultaneously optimizing network resource utilization and traffic performance.

The goal of TE is to compute a path from one given node to another (source routing), such that the path does not violate the constraints (e.g. Bandwidth/administrative requirements...) and is optimal with respect to some scalar metric. Once the path is computed, TE (Constraint based routing) is responsible for establishing and maintaining forwarding state along such a path.

In order to support Traffic engineering,  besides explicit routing (source routing), the following components should be available:

• Ability to compute a path at the source by taking into account all the constraints.  To do so the source need to have all the information either available locally or obtained from other routers in the network (e.g. Network topology)
• Ability to distribute the information about network topology and attributes  associated with links throughout the network once the path is computed, need a way to support forwarding along such a path
• Ability to reserve network resources and to modify link attributes (as the result of certain traffic taking certain routes)

For this purpose below technologies/protocols are used in MPLS-TE.

• Constraint shortest path first algorithm used in path calculation. This is a modified version of the well known SPF algorithm extended to constraints support
• RSVP extension(RSVP-TE) used to establish the forwarding state along the path, as well as to reserve resources along the path.
• Link state IGPs with extension (OSPF with LSAs, IS-IS with  Link State Packets TLV (type, length, value)) keep track  of topology changes propagation. example CR-OSPF and CR-IS-IS.