Alteon Application Switch Operating System Application Guide
Server Load Balancing
Document ID: RDWR-ALOS-V2900_AG1302 167
Alteon with SLB software acts as a front-end to the servers, interpreting user session requests and
distributing them among the available servers. Load balancing in Alteon can be done in the following
ways:
• Virtual server-based load balancing—This is the traditional load balancing method. Alteon is
configured to act as a virtual server and is given a virtual server IP address (or range of
addresses) for each collection of services it distributes. Depending on your Alteon platform,
there can be as many as 1023 virtual servers on Alteon, each distributing up to eight different
services.
Each virtual server is assigned a list of the IP addresses (or range of addresses) of the real
servers in the pool where its services reside. When the user stations request connections to a
service, they communicate with a virtual server on Alteon. When Alteon receives the request, it
binds the session to the IP address of the best available real server and remaps the fields in
each frame from virtual addresses to real addresses.
HTTP, IP, FTP, RTSP, IDS, and static session WAP are examples of some of the services that use
virtual servers for load balancing.
• Filter-based load balancing—A filter allows you to control the types of traffic permitted
through Alteon. Filters are configured to allow, deny, or redirect traffic according to the IP
address, protocol, or Layer 4 port criteria. In filter-based load balancing, a filter is used to
redirect traffic to a real server group. If the group is configured with more than one real server
entry, redirected traffic is load balanced among the available real servers in the group.
Firewalls, WAP with RADIUS snooping, IDS, and WAN links use redirection filters to load balance
traffic.
• Content-based load balancing—Content-based load balancing uses Layer 7 application data
(such as URL, cookies, and Host Headers) to make intelligent load balancing decisions.
URL-based load balancing, browser-smart load balancing, and cookie-based preferential load
balancing are a few examples of content-based load balancing.
Implementing Server Load Balancing
This section includes basic SLB implementation procedures, as well as customized SLB options. To
implement basic Server Load Balancing, see Basic Server Load Balancing Topology, page 168
.
The following configuration options can be used to customize SLB in Alteon:
• Basic Server Load Balancing Topology, page 168
• Network Topology Requirements, page 169
• Server Load Balancing Configuration Basics, page 171
• Physical and Logical Real Server Modes, page 174
• Supported Services and Applications, page 175
• Disabling and Enabling Real Servers, page 176
• Health Checks for Real Servers, page 176
• Multiple Services per Real Server, page 177
• Buddy Server Health Checks, page 177
• Metrics for Real Server Groups, page 180
• Group Availability Threshold, page 183
• Weights for Real Servers, page 184
• Connection Time-Outs for Real Servers, page 184
• Maximum Connections for Real Servers, page 185
• Unlimited Connections to Real Servers, page 186
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