MPLS-Enabled Applications: Emerging Developments and New Technologies

4.4. THE DiffServ-TE SOLUTION

This section examines how per-traffic-type behavior is enforced, both when setting up an LSP and when forwarding traffic.

4.4.1. Class types

The basic DiffServ-TE requirement is to be able to make separate bandwidth reservations for different classes of traffic. This implies keeping track of how much bandwidth is available for each type of traffic at any given time on all routers throughout the network. [RFC3564] spells out the requirements for support of DiffServ Aware MPLS-TE and defines the fundamental concepts of the technology.

For the purpose of keeping track of the available bandwidth for each type of traffic, [RFC3564] introduces the concept of a class type (CT). [RFC3564] does not mandate a particular mapping of traffic to CTs, leaving this decision to the individual vendors. One possible implementation is to map traffic that shares the same scheduling behavior to the same CT. In such a model one can think of a CT in terms of a queue and its associated resources. Because the PHB is defined by both the queue and the drop priority, a CT might carry traffic from more than one DiffServ class of service, assuming that they all map to the same scheduler queue.

The IETF standards require support of up to eight CTs referred to as CT0 through CT7. LSPs that are traffic-engineered to guarantee bandwidth from a particular CT are referred to as DiffServ-TE LSPs. In the current IETF model, a DiffServ-TE LSP can only carry traffic from one CT. LSPs that ...