5.3 APPLICABILITIES

This section describes MPLS applicabilities including traffic engineering, resilience, and Ethernet emulation.

As described in Section 5.1, traffic engineering is one of the key MPLS applications. First, it is important to discuss how traffic engineering is achieved in the MPLS network. OSPF that is used in an IP network [2], is extended to distribute more detailed attributes of links [3]. A link that is specified by the extended attributes is called a traffic engineering (TE) link. The extended attributes for a TE link include TE metric, maximum bandwidth, maximum reservable bandwidth, unreserved bandwidth, and distractive group. All routers share attributes of each TE link in the MPLS network. When an LSP is requested to be set up between source and destination routers, the source router computes the shortest path that satisfies the requirements based on the distributed TE link information. The path computation is called Constraint-based Shortest Path First (CSPF). By setting up the LSP based on CSPF policy, any network congestion is avoided and QoS is maintained in the MPLS network. On the other hand, since IP packets are routed based on the shortest path first policy in an IP network, some network congestion can occur, and QoS may not be maintained.