Multiclass LSP Overview
A multiclass LSP is an LSP that can carry several class types. One multiclass LSP can be used to support up to four class types. On the packets, the class type is specified by the EXP bits (also known as the class-of-service bits) and the per-hop behavior (PHB) associated with the EXP bits. The mapping between the EXP bits and the PHB is static, rather than being signaled in RSVP.
Once a multiclass LSP is configured, traffic from all of the class types can:
- Follow the same path
- Be rerouted along the same path
- Be taken down at the same time
Class types must be configured consistently across the Differentiated Services domain, meaning the class type configuration must be consistent from router to router in the network.
You can unambiguously map a class type to a queue. On each node router, the CoS queue configuration for an interface translates to the available bandwidth for a particular class type on that link.
The combination of a class type and a priority level forms a traffic engineering class. The IGPs can advertise up to eight traffic engineering classes for each link.
For more information about the EXP bits, see Label Allocation.
For more information about forwarding classes, see the Junos OS Class of Service Configuration Guide.
