Differentiated-Services-Aware Traffic Engineering Overview

Differentiated services give different treatment to traffic based on the EXP bits in the MPLS label header and allow you to provide multiple classes of service.

Differentiated-services-aware traffic engineering provides the following features:

• Traffic engineering at a per-class level rather than at an aggregate level.
• Different bandwidth constraints for different class types (traffic classes).
• Different queuing behaviors per class, allowing the router to forward traffic based on the class type.

In comparison, standard traffic engineering does not consider CoS, and it completes its work on an aggregate basis across all differentiated service classes.

Differentiated-services-aware traffic engineering provides the following advantages:

• Traffic engineering can be performed on a specific class type instead of at the aggregate level.
• Bandwidth constraints can be enforced on each specific class type.
• It forwards traffic based on the EXP bits.

This makes it possible to guarantee service and bandwidth across an MPLS network. With differentiated-services-aware traffic engineering, among other services, you can provide ATM circuit emulation, VoIP, and a guaranteed bandwidth service.

The following describes how the IGP, Constrained Shortest Path First (CSPF), and Resource Reservation Protocol (RSVP) participate in differentiated-services-aware traffic engineering:

• The IGP can advertise the unreserved bandwidth for each traffic engineering class to the other members of the differentiated services domain. The traffic engineering database (TED) stores this information.
• A CSPF calculation is performed considering the bandwidth constraints for each class type. If all the constraints are met, the CSPF calculation is considered successful.
• When RSVP signals an LSP, it requests bandwidth for specified class types.