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Example: Building a Four-Level Hierarchy of Schedulers


This section provides a more complete example of building a 4-level hierarchy of schedulers. The configuration parameters are shown in Figure 1. The queues are shown at the top of the figure with the other three levels of the hierarchy below.

Figure 1: Building a Scheduler Hierarchy
Building a Scheduler Hierarchy

The figure’s PIR values are configured as the shaping rates and the CIRs are configured as the guaranteed rate on the Ethernet interface ge-1/0/0. The PIR can be oversubscribed (that is, the sum of the children PIRs can exceed the parent’s, as in svlan 1, where 200 + 200 + 100 exceeds the parent rate of 400)). However, the sum of the children node level’s CIRs must never exceed the parent node’s CIR, as shown in all the service VLANs (otherwise, the guaranteed rate could never be provided in all cases).

This configuration example presents all details of the CoS configuration for the interface in the figure (ge-1/0/0), including:

Configuring the Interface Sets

Configuring the Interfaces

The keyword to configure hierarchical schedulers is at the physical interface level, as is VLAN tagging and the VLAN IDs. In this example, the interface sets are defined by logical interfaces (units) and not outer VLAN tags. All VLAN tags in this example are customer VLAN tags.

Configuring the Traffic Control Profiles

The traffic control profiles hold parameters for levels above the queue level of the scheduler hierarchy. This section defines traffic control profiles for both the service VLAN level (logical interfaces) and the customer VLAN (VLAN tag) level.

Configuring the Schedulers

The schedulers hold the information about the queues, the last level of the hierarchy. Note the consistent naming schemes applied to repetitive elements in all parts of this example.

Configuring the Drop Profiles

This section configures the drop profiles for the example. For more information about interpolated drop profiles, see Managing Congestion Using RED Drop Profiles and Packet Loss Priorities.

Configuring the Scheduler Maps

This section configures the scheduler maps for the example. Each one references a scheduler configured in Configuring the Schedulers.

Applying the Traffic Control Profiles

This section applies the traffic control profiles to the proper levels of the hierarchy.


Although a shaping rate can be applied directly to the physical interface, hierarchical schedulers must use a traffic control profile to hold this parameter.


You should be careful when using a show interfaces queue command that references nonexistent class-of-service logical interfaces. When multiple logical interfaces (units) are not configured under the same interface set or physical interface, but are referenced by a command such as show interfaces queue ge-10/0/1.12 forwarding-class be or show interfaces queue ge-10/0/1.13 forwarding-class be (where logical units 12 and 13 are not configured as a class-of-service interfaces), these interfaces display the same traffic statistics for each logical interface. In other words, even if there is no traffic passing through a particular unconfigured logical interface, as long as one or more of the other unconfigured logical interfaces under the same interface set or physical interface is passing traffic, this particular logical interface displays statistics counters showing the total amount of traffic passed through all other unconfigured logical interfaces together.