Geographic Load Balancing - Coyote Point Systems Equalizer Installation And Administration Manual

Chapter 1:Overview
For HTTP requests, load balancing decisions can be based on:
HTTP protocol version
Host name
Pathname of the request
Filename of the request
Pattern matches against arbitrary HTTP request headers
For HTTPS requests, load balancing decisions can also be based on the SSL protocol level
used by the client to connect.
Rules for Layer 7 load balancing are defined through the Equalizer Administration
Interface. For more information about specifying Layer 7 rules, see "Specifying Layer 7
Rules" on page 79.

Geographic Load Balancing

With Envoy installed, Equalizer supports geographic clustering and load balancing to
enable requests to be automatically distributed across servers in different physical
locations. This can dramatically improve reliability by ensuring that your service remains
available even if a site-wide failure occurs. Equalizer can also improve performance by
routing requests to the location with the least network latency.
An Equalizer site is a cluster of servers under Equalizer control. A geographic cluster is a
collection of sites that provide a common service, such as a web site. The different sites in a
geographic cluster are often separated by large distances. For example, a geographic
cluster might contain two sites, one in the U.S. and one in Europe:
Figure 1 Geographic cluster with two sites
Each incoming request is routed to the site best able to handle it. If a site is unavailable or
overloaded, Equalizer routes requests to the other sites in the geographic cluster.
6
Internet
nvoy
Site 2
nvoy
Site 1
Equalizer Installation and Administration Guide