MPLS-Enabled Applications: Emerging Developments and New Technologies

4.2. THE BUSINESS DRIVERS

Traditionally, IP/MPLS-based networks were used only for services with relatively relaxed requirements in terms of delay, jitter or bandwidth guarantees. Increasingly, providers have started carrying a wider range of services, such as PSTN-quality voice or providing ATM/FR or Ethernet over the MPLS core. The driver for offering these services is the cost savings achieved by eliminating the need to have several separate physical networks. Indeed, one of the most attractive promises of MPLS is the ability to converge all services on to a common core. The challenge lies in the fact that most of these services often require stricter service-level agreements (SLAs) than the previous norm on IP/MPLS networks.

The SLAs define the service quality experienced by traffic transiting the network and are expressed in terms of latency, jitter, bandwidth guarantees, resilience in the face of failure, and down time. The SLA requirements translate to two conditions: (a) different scheduling, queuing and drop behavior based on the application type and (b) bandwidth guarantees on a per-application basis.

To date, service providers have rolled out revenue-generating services in their networks using DiffServ alone. By assigning applications to different classes of service and marking the traffic appropriately, condition (a) was met. However, this approach assumes that there are enough resources to service the traffic according to the marking. If the traffic follows a congested ...