Geographic Load Balancing - Coyote Point Systems E350GX Installation And Administration Manual

on information from the application layer. This provides access to the actual data payloads of the TCP/UDP packets
exchanged between a client and server. For example, by examining the payloads, a program can base load-balancing
decisions for HTTP requests on information in client request headers and methods, server response headers, and
page data.
Equalizer's Layer 7 load balancing allows administrators to define rules in the administration interface for routing
HTTP and HTTPS requests according to the request content. These rules are called match rules. A match rule might,
for example, route requests based on whether the request is for a text file or a graphics file:
•
load balance all requests for text files (html, etc.) across servers A and B
•
load balance all requests for graphics files across servers C, D, and E
•
load balance all other requests across all of the servers
Match Rules are constructed using match functions that make decisions based on the following:
• HTTP protocol version; for HTTPS connections, the SSL protocol level the client uses to connect.
• Client IP address
• Request method (GET, POST, etc.)
• All elements of the request URI (host name, path, filename, query, etc.)
• Pattern matches against request headers
Match functions can be combined using logical constructs (AND, OR, NOT, etc.) to create extremely flexible cluster
configurations. Please see "Using Match Rules" on page 207 for an overview of Match Rules, a complete list of
match functions, and usage examples.

Geographic Load Balancing

The optional Envoy add-on supports , which enables requests to be automatically distributed across Equalizer sites
in different physical locations. An Equalizer site is a cluster of servers under a single Equalizer's control. A is a
collection of sites that provide a common service, such as Web sites. The various sites in a geographic cluster can be
hundreds or even thousands of miles apart. For example, a geographic cluster might contain two sites, one in the
eastern U.S. and one on the U.S.'s west coast (Figure 1).
Geographic load balancing 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.
Envoy
Site A
Figure 1 Geographic cluster with two sites
Equalizer Installation and Administration Guide
Internet
Introducing Equalizer
Envoy
Site B
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