Variables Of The Simple Shared Shaper Algorithm; Configuring Variables In The Simple Shared Shaping Algorithm - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - QUALITY OF SERVICE CONFIGURATION GUIDE 2010-09-22 Configuration Manual

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Variables of the Simple Shared Shaper Algorithm

Copyright © 2010, Juniper Networks, Inc.
Variables of the Simple Shared Shaper Algorithm on page 87
Configuring Simple Shared Shaper Algorithm Variables on page 89
The formulas the simple shared shaper uses contain values maintained by the simple
shared shaper algorithm, and variables that you configure.
The following factors are maintained by the simple shared shaper algorithm:
newMeasuredRate—Sum of bytes enqueued to non-best-effort constituent queues,
in bps.
oldDynamicRate—Dynamic shaping rate from the previous rate period, in
bits-per-second.
sharedShapingRate—Configured shared shaper rate, in bps. The shared shaping rate
is the total rate of all constituents of the shared shaper.
You can configure the following variables, which correspond to the commands described
in "Configuring Simple Shared Shaper Algorithm Variables" on page 89.
convergenceFactor—Controls the convergence of the dynamic shaping rate to the
calculated shaping rate, expressed as a percentage of the available bandwidth.
The default value of 50 percent causes the dynamic shaping rate to converge by half
of the available rate each period. For example, when the dynamic rate of a 5 Mbps
simple shared shaper is 1 Mbps, and the measured rate goes from 4 Mbps to 0 Mbps,
4 Mbps of bandwidth becomes available. The simple shared shaper converges from 1
Mbps to 5 Mbps by half of the available bandwidth per period. In this example, the
dynamic shaping rates for several periods are 1 Mbps, 3 Mbps, 4 Mbps, 4.5 Mbps, 4.75
Mbps, and so on.
maximumVOQL—Sets the maximum virtual output queue length (VOQL), expressed
in milliseconds (ms) of the shared shaping rate.
The default value of 4000 indicates that a 5 Mbps shared shaper does not allow the
VOQL to exceed 20 Mbps. Smaller values reduce the effect of the VOQL in the simple
shared shaper algorithm.
A maximum VOQL of 0 indicates that the shared shaper ignores the VOQL. This setting
is appropriate for configurations where exceeding the shared shaping rate for brief
periods of time does not cause downstream queuing.
minimumDynamicRate—Sets the minimum value for the dynamic shaping rate,
expressed as a percentage of the shared shaping rate. For example, a value of 25 for
a 20 Mbps shared shaper specifies that the dynamic shaping rates never be set to a
value less than 5 Mbps. The default value is 0.
reactionFactor—Controls how the simple shared shaper reacts to changing rates,
expressed as a percentage. The default value of 200 changes the algorithm to use
200 percent of the changing rate.
Chapter 11: Configuring Variables in the Simple Shared Shaping Algorithm
87