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Managing System Resources for Shadow Nodes
Copyright © 2010, Juniper Networks, Inc.
Figure 42: Shadow Nodes
Unlike phantom nodes, shadow nodes can alter the behavior of the scheduler.
The first scheduler hierarchy in Figure 42 on page 143 shows VLAN interfaces A, B and C
stacked above the same S-VLAN interface. Interfaces A and B have the same scheduler
hierarchy (referencing qos-profile AB) and have a VLAN queue stacked directly above
the S-VLAN node. In this case, VLAN interfaces A, B and C share the same 33 percent
bandwidth available to the S-VLAN node.
Interface C has a VLAN queue stacked above a VLAN node and the S-VLAN node
(referencing qos-profile C).
Specifying a shadow node forces the VLAN queue to the proper scheduler level. The
second scheduler hierarchy in Figure 42 on page 143 shows the shadow node that is applied
after QoS profile AB-shadow is assigned to interfaces A and B. As a result, interfaces A
and B have 25 percent of the S-VLAN bandwidth and interface C has 50 percent of the
S-VLAN bandwidth.
The S-VLAN shadow node uses the same scheduler profile as the queue.
To provide interfaces A and B with the proper weight, configure the weight of the shadow
node to the sum of its queue weight. You can use hierarchical parameter instances and
weight expressions to configure an appropriate weight.
For a list of interface types supported for shadow nodes, see Supported Interface Types
for QoS Profiles on page 125
For more information about hierarchical parameters, see Hierarchical QoS Parameters
Overview on page 245
Each ASIC hardware type provides different node and queue resources.
Level 1 queues stack directly above the port; level 2 queues stack above a node and the
port. The router implicitly creates the level 1 and level 2 queues.
Chapter 17: Configuring Shadow Nodes for Queue Management
143
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