Juniper JUNOSE 11.1.X - QUALITY OF SERVICE CONFIGURATION GUIDE 3-21-2010 Configuration Manual page 67

As shown in Figure 7 on page 36, queue lengths extend to oversubscribe memory
when aggregate memory utilization is low, and contract to strictly partition memory
when memory utilization is high. Dynamic thresholding enforces fairness when free
buffers are scarce and promotes sharing when buffers are plentiful. Dynamic queue
thresholds are discussed in "Queuing and Buffer Management Overview" on page 17.
Figure 7 on page 36 illustrates WRED behavior with dynamic queue thresholding.
To configure WRED to run on queues whose limits dynamically expand and contract,
use the percent keyword when you configure thresholds in a drop profile. For
example:
host1(config)#drop-profile internetDropProfile
host1(config-drop-profile)#average-length-exponent 9
host1(config-drop-profile)#committed-threshold percent 30 90 4
host1(config-drop-profile)#conformed-threshold percent 25 90 5
host1(config-drop-profile)#exceeded-threshold percent 20 90 6
Example: Configuring WRED and Dynamic Queue Thresholds
Chapter 4: Configuring Dropping Behavior with RED and WRED
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