Virtual private networks (VPNs) are a popular way for enterprises to interconnect remote sites. Traditionally, VPNs have been based on frame relay, asynchronous transfer mode (ATM) or time division multiplex (TDM) private lines, using the service provider's ATM core network, and accounting for the majority of their data service revenues. However, the influences of a highly dynamic telecommunications market have raised demands for increased flexibility while controlling costs. New revenue opportunities are emerging for service providers to differentiate their offerings through services such as IP VPNs and virtual private LAN services (VPLSs), while achieving operational efficiencies though convergence of all services on a common multi-protocol label switching (MPLS) backbone. However, existing technologies, such as ATM, provide highly profitable services which must continue to be supported. The authors describe how network and service interworking can help to deliver profitable services over the new converged network.
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