MPLS introduces connection orientation and packet switching in IP networks. IP datagrams are forwarded by MPLS routers along pre-established paths, based on a short label. This reduces the amount of routing computations, which are carried out only at the times of setting up new paths. MPLS allows to introduce new traffic engineering techniques for IP networks [52], [53], and [54]. In particular, also those techniques which apply for connection-oriented networks can be applied to MPLS networks. One of these techniques is dynamic routing. Another important application for MPLS networks is the configuration of Virtual Private Networks (VPNs) over a public IP network. The benefit of MPLS for this application is that private IP addresses, which may not be unique, are separated from the world-wide valid public IP addresses used in the public IP network. The separation of addresses is realised by building MPLS tunnels through the public IP network. The MPLS protocol can also be run on ATM networks and frame relay networks. This simplifies the interworking between these networks and EP networks. An overview of the MPLS Internet architecture can be found in [55].