Juniper JUNOSE 11.1.X - QUALITY OF SERVICE CONFIGURATION GUIDE 3-21-2010, Configuration Manual

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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 151 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 151 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.
Related Topics
For a list of interface types supported for shadow nodes, see Supported Interface
Types for QoS Profiles on page 131
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For more information about hierarchical parameters, see Hierarchical QoS
Parameters Overview on page 261
Managing System Resources for Shadow Nodes
Each ASIC hardware type provides different node and queue resources.
Managing System Resources for Shadow Nodes
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Chapter 17: Configuring Shadow Nodes for Queue Management