MPLS-Enabled Applications: Emerging Developments and New Technologies

11.2. THE BUSINESS DRIVERS

Native Layer 2 services have existed for several years, based on Frame Relay or ATM. Often these services are used by an enterprise to build its corporate Layer 2 VPN by interconnecting its LANs over a wide area. Service providers can offer near global reach, either directly or through interconnection agreements with partners. The services are a valuable source of revenue to service providers, at the time of writing far outstripping revenues from IP services. In these networks, customer sites are interconnected at Layer 2, sometimes in a full mesh but more typically in a hub-and-spoke topology. The role of the service provider is to transport the ATM cells or Frame Relay frames over the wide area, at an agreed bit-rate for each circuit.

As well as being used to carry general LAN interconnection traffic, these services, especially in the ATM case, are sometimes used to carry traffic requiring more stringent SLAs from the network, e.g. with respect to delay variation, such as video traffic or Private Automatic Branch eXchange (PABX) interconnections.

In many cases, a service provider can migrate these services to an MPLS network while retaining the same connectivity, as far as the customer is concerned, and maintaining similar service characteristics. In these cases, the presentation to the customer is still over ATM or Frame Relay and a similar service-level agreement (SLA) is offered. For example, in the Frame Relay case, a CIR (committed information ...