Specifications

Chapter 9: Administering Geographic Clusters
156 Equalizer Installation and Administration Guide
• round trip: This method weights the client’s network proximity more heavily than other
criteria. This option only works if you enable Ping Triangulation.
• adaptive: This method takes all available information into account when selecting a site.
This setting is a reasonable default.
• site load: This method weights the current load at each site more heavily than other
criteria.
• site weight: This method weights the user-defined static weight for each site more
heavily than other criteria.
8. Check or clear the ICMP triangulation checkbox. When you check ICMP triangulation, each
Envoy site pings the client and collects latency information, which provides more accurate
client location information. If you do not want to allow Equalizer to ping clients when they
make a request, clear the ICMP triangulation checkbox.
9. Click the commit button to add the geographic cluster. An entry for the new geographic cluster
appears in the left frame.
Equalizer can refuse an Add GeoCluster command for several reasons, including:
• Attempting to add a cluster for a FQDN that is already configured
• Attempting to add more clusters than are supported by Equalizer
Configuring a Geographic Cluster’s Load-Balancing Options
You can change the load balancing policy and response settings for a geographic cluster from the
geocluster screen. Configure these parameters independently for each geographic cluster. (For more
information about the load balancing policy and response settings, see “Adding a Geographic
Cluster” on page 155.)
You might want to fine-tune the static weights of the geographic cluster’s sites to optimize cluster
performance. For more information, see “Adjusting a Site’s Static Weight” on page 159.
To change a geographic cluster’s load-balancing options, follow these steps:
1. Log into the Equalizer Administration Interface in edit mode.
2. In the left frame, click the link formed by the domain name associated with the geographic
cluster. The geocluster screen opens in the right frame.
3. Select Change GeoCluster Parameters from the local menu. The modify geocluster screen
appears in the right frame.
4. Specify the responsiveness, which controls how aggressively Equalizer adjusts the site’s
dynamic weights: Slowest, Slow, Medium, Fast, and Fastest. The faster settings enable
Equalizer to adjust its load balancing criteria more frequently and permit a greater variance in
the relative weights assigned to sites. A slow setting causes site measurements to be averaged
over a longer period of time before Equalizer applies them to the cluster-wide load balancing
and tend to ignore spikes in cluster measurements caused by intermittent network glitches.
5. Specify the
DNS cache ttl (cache time-to-live), which is the length of time, in seconds, that the
client’s DNS server should cache the resolved IP address. Longer times will result in increased
failover times in the event of a site failure, but are more efficient in terms of network resources.
A reasonable value would be 120 (that is, 2 minutes).