Simple Shared Shaper Algorithm Calculations; Figure 23: Less Conservative Simple Shared Shaper Behavior; Figure 24: More Liberal Simple Shared Shaper Behavior - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - QUALITY OF SERVICE CONFIGURATION GUIDE 2010-09-22 Configuration Manual

JunosE 11.3.x Quality of Service Configuration Guide

Simple Shared Shaper Algorithm Calculations

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When the video stream starts in the example displayed by Figure 22 on page 85, 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 86. 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 86. 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

The simple shared shaper algorithm performs the following tasks to calculate the dynamic
rate:
Calculates the new measured rate.
1.
Calculates the virtual output queue length (VOQL).
2.
Calculates the new dynamic rate.
3.
Uses the larger value of the new dynamic rate (from Step 3) and a minimum dynamic
4.
rate.
Copyright © 2010, Juniper Networks, Inc.