Scheduler Node Scaling on the Trio MPC/MIC Interfaces Overview
The Trio MPC/MIC interface hardware (but not the Trio DPC) supports multiple levels of scheduler nodes. In per-unit-scheduling mode, each logical interface (unit) can have 4 or 8 queues and has a dedicated level 3 scheduler node. Scheduler nodes can be a one of four levels: the queue itself (level 4), the logical interface or unit (level 3), the interface set or virtual LAN (VLAN) collection (level 2), or the physical interface or port (level 1). For more information about hierarchical scheduling levels, see Configuring Hierarchical Schedulers for CoS.
The Trio MPC/MIC interface hardware supports enhanced queuing in both per-unit scheduling and hierarchical scheduler modes. The way that the scheduler hierarchy is built depends on the scheduler mode configured.
In per-unit scheduling mode, each logical interface unit has its own dedicated level 3 node and all logical interface units share a common level 2 node (one per port). This scheduling mode is shown in Figure 1.
Figure 1: Trio DPC and MPC/MIC interface Per-unit Scheduler Node Scaling
In this case, in per-unit scheduling mode, the level 2 node is a dummy node.
The case with hierarchical scheduling mode, for a similar configuration when there are no interface sets configured and only the logical interfaces have traffic control profiles is shown in Figure 2.
Figure 2: Trio DPC and MPC/MIC interface Hierarchical Scheduling Node Scaling
When an interface set has a CoS scheduling policy but none of its child logical interfaces has a CoS scheduling policy, then the interface set is considered to be a leaf node and has one level 2 and one level 3 node.
In per-unit scheduling, the logical interfaces share a common level 2 node (one per port). In hierarchical-scheduling mode, each logical interface has its own level 2 node. So scaling is limited by the number of level 2 nodes. For hierarchical schedulers, in order to better control system resources in hierarchical-scheduling mode, you can limit the number of hierarchical levels in the scheduling hierarchy to two. In this case, all logical interfaces and interface sets with CoS scheduling policy share a single (dummy) level 2 node, so the maximum number of logical interfaces with CoS scheduling policies is increased (the interface sets must be at level 3). To configure scheduler node scaling, include the hierarchical-schedulers statement with the maximum-hierarchy-levels option at the [edit interfaces xe-fpc/pic/port] hierarchy level. The only supported value is 2.
 | Note: Level 3 interface sets are supported by the maximum-hierarchy-levels option, but level 2 interface sets are not supported. If you configure level 2 interface sets with the maximum-hierarchy-levels option, you generate Packet Forwarding Engine errors. |
