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

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When the video stream starts in the example displayed by Figure 22 on page 89,
the shared shaper reacts by drastically reducing best-effort traffic because it must
avoid saturating downstream queues. In some cases, best-effort traffic is throttled
for a few seconds. When the video stream stops, best-effort traffic can continually
consume more bandwidth, up to the shared-shaping rate.
By controlling the minimum dynamic rate in the simple shared shaper algorithm,
you can configure the less conservative simple shared shaping behavior displayed
in Figure 23 on page 90. In this example, as the video traffic starts, the best-effort
rate is reduced less drastically, and best-effort traffic is not starved.
Figure 23: Less Conservative Simple Shared Shaper Behavior
You can also configure the more liberal simple shared shaper behavior that is
displayed in Figure 24 on page 90. In this example, the initial over-limit video traffic
is ignored. When the video traffic stops, the system immediately allows best-effort
traffic to consume the available bandwidth.
Figure 24: More Liberal Simple Shared Shaper Behavior
Simple Shared Shaper Algorithm Calculations
The simple shared shaper algorithm performs the following tasks to calculate the
dynamic rate:
1.
Calculates the new measured rate.
2.
Calculates the virtual output queue length (VOQL).
3.
Calculates the new dynamic rate.
4.
Uses the larger value of the new dynamic rate (from Step 3) and a minimum
dynamic rate.
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Simple Shared Shaping Algorithm Overview
JUNOSe 11.1.x Quality of Service Configuration Guide