Trainet, a new scheme to extend MPLS (multi-protocol label switching) is presented. The scheme works much like the subway system in a large metropolitan area. Each (unidirectional) subway line corresponds to a labeled path, and a route in the network is defined by either a pair >label, count-value<, where count specifies how many hops a packet still has to take in the specified train, or a route may be defined by a sequence of such pairs. A sequence of such pairs specifies that the packet has to take a number of hops in one train-line, and then continue for a certain number of hops on another train-line and so forth. While slightly increasing the number of labels in a header and adding a counter to each label, the scheme reduces the total number of different labels necessary in the network, and in each switch. Thus, for a given number of labels it may support a larger number of flows. Moreover, our scheme considerably simplifies the path set-up cost while still providing all the features of MPLS: switching, supporting QoS, explicit routing, and traffic engineering.
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