Coyote Point Systems Equalizer GX Series, Administration Manual

Page: 24 / 866

Overview
Intelligent Load Balancing
The Equalizer appliance functions as a gateway to one or more sets of servers organized into
virtual clusters. When a client submits a request to a site that the appliance manages, it identifies
the virtual cluster for which the request is intended, determines the server in the cluster that will
be best able to handle the request, and forwards the request to that server for processing.
To route the request, the appliance modifies the header of the request packet with the appropriate
server information and forwards the modified packet to the selected server. Depending on the
cluster options chosen, it may also modify the headers in server responses on the way back to the
client.
Equalizer supports clusters that route requests based on either Layer 4 (TCP or UDP) or Layer 7
(HTTP or HTTPS) protocols. Layer 4 is also referred to as the Transport Layer, while Layer 7 is
referred to as the Application Layer. These terms come from the OSI and TCP/IP Reference
Models, abstract models for network protocol design.
In general, Layer 4 clusters are intended for configurations where routing by the destination IP
address of the request is sufficient and no examination of the request headers is required. Layer 7
clusters are intended for configurations where routing decisions need to be made based on the
content of the request headers. the appliance evaluates and can modify the content of request
headers as it routes packets to servers; in some cases, it can also modify headers in server
responses on their way back to the client.
Feature
Cluster Type
L4 UDP L4, L7 TCP L7 HTTP L7 HTTPS
Load balancing
policies Round Robin, Static Weight, Adaptive, Fastest response,
Least Connections, Server Agent, Custom
Server failure
detection (probes)
ICMP, TCP, Health Check ICMP, TCP, ACV, Health Check
Persistence Based on IP Using Cookies
Server selection by
request content
(i.e., Match Rules)
No; load is balanced according to current load balancing policy.
Yes; load is balanced
according to decisions
made by examining request
content.
Load balanced
protocols
Ideal for stateless UDP-
based protocols, such as
DNS and RADIUS; WAP
gateways; NFS server
clusters that provide a
single-system image.
Ideal for stateful TCP-based
protocols, such as HTTP,
HTTPS, SMTP, FTP,
LDAP/LDAPS
and others.
HTTP HTTPS
NAT and spoofing
Yes
Basic Capabilities of Cluster Types Supported by Equalizer
24 Copyright © 2014 Coyote Point Systems, A Subsidiary of Fortinet, Inc.