ServerIron ADX Global Server Load Balancing Guide 137
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Smoothing mechanism for RTT measurements 1
Specifying the ramp-up-factor
The ramp-up factor specifies the increments in which successively new high RTT samples should
be factored into the existing RTT value. If you want to specify the ramp-up factor, enter commands
such as the following on the GSLB ServerIron ADX.
GSLB-ServerIronADX# configure terminal
GSLB-ServerIronADX(config)# gslb site sanjose
GSLB-ServerIronADX(config-gslb-site-sanjose)# ramp-up-factor 4
Syntax: [no] ramp-up-factor <value>
Enter a number from 1-10 for <value>. The default is 2.
Specifying the ramp-down factor
The ramp-down factor specifies the factor by which successively new very low RTT samples should
be factored into the existing RTT value. If you want to specify the ramp-down factor, enter the
following on the GSLB ServerIron ADX.
GSLB-ServerIronADX# configure terminal
GSLB-ServerIronADX(config)# gslb site sanjose
GSLB-ServerIronADX(config-gslb-site-sanjose)# ramp-down-factor 4
Syntax: [no] ramp-down-factor <value>
Enter a number from 1-10 for <value>. The default is 3.
Simulating RTT smoothing
You can test an enhanced RTT smoothing configuration for a Site ServerIron ADX before it is
deployed by running the RTT smoothing simulator. This simulator is a tool that allows you to apply
the new RTT smoothing mechanism for a GSLB Site on a set of sample RTT values. This simulator
aids in determining the optimal values of enhanced RTT smoothing parameters such maximum
deviation allowed, maximum ignore count, normal ramp factor, ramp up factor and ramp down
factor. You can also use the simulator as a debugging tool to determine how a particular RTT value
was derived. You can also compare the new and existing RTT smoothing mechanism results using
this simulator and determine which of the two mechanisms is more suitable for your network.
Before using the simulator, you may first configure the desired enhanced RTT smoothing
parameters (maximum deviation allowed, maximum ignore count, normal ramp factor, ramp up
factor, and ramp down factor) for the GSLB Site. If you do not configure any enhanced RTT
smoothing parameters for the Site, then the default values for the parameters are used during
simulation.
To start the simulation for a GSLB Site, enter the following on the GSLB ServerIron ADX.
GSLB-ServerIronADX# configure terminal
GSLB-ServerIronADX(config)# gslb simulate-rtt-smoothing test 5
GSLB-ServerIronADX(config-gslb-rtt-sim-test)#
Syntax: gslb simulate-rtt-smoothing <site-name> <initial-rtt-value>
Enter the name of the GSLB site for <site-name>.
Enter <initial-rtt-value>Initial RTT value
After enabling the simulator, the GSLB enters the enhanced RTT simulation mode for the GSLB Site
specified. Also, by default, the enhanced smoothing mechanism is disabled during simulation. To
enable the enhanced smoothing mechanism for simulation, enter the following on the GSLB
ServerIron ADX.
GSLB-ServerIronADX(config-gslb-rtt-sim-test)# enable-sim-new-rtt-smooth