What Is Load Balancing; How Wan Link Load Balancing Works; Outbound Traffic - Radware Alteon Application Manual

What is Load Balancing?

Alteon acts as a front-end to the WAN links, interpreting user session requests and distributing them
among the available WAN links. Load balancing in Alteon can be done in the following ways:
• Filtered-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 filtered-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.
WAN links use redirection filters to load balance outbound traffic. For more information, see
Outbound Traffic, page
• 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 will distribute. There can be as many as 1024 virtual
servers, each distributing up to eight different services (up to a total of 1023 services).
Each virtual server is assigned a real server. When the user stations request connections to a
service, they will communicate with an Alteon virtual server. When Alteon receives the request,
it binds the session to the IP address of the corresponding real server and remaps the fields in
each frame from virtual addresses to real address.
This method of load balancing is used to load balance inbound traffic. For more information, see
Inbound Traffic, page

How WAN Link Load Balancing Works

To effectively use multiple ISP links, Radware recommends that both outbound and inbound traffic is
load balanced using Alteon. Alteon can be configured to load balance up to eight ISP links. Alteon
regularly checks the health of the upstream routers and measures the condition of the link. When
traffic is to be sent to the link, Alteon chooses the most optimal link for that session.
This section explains how WAN link load balancing works differently for:
• Outbound Traffic, page 633
• Inbound Traffic, page 634

Outbound Traffic

Outbound traffic is data from the intranet that accesses content across the Internet. Alteon load
balances outbound traffic using redirection filters to redirect traffic initiated from within the user's
network to a group of devices that exist at the other end of the WAN link. These filters determine
which link is the best at the time the request is generated.
The design of outbound WAN link load balancing is identical to standard redirection, except that
Alteon substitutes the source IP address of each frame with the proxy IP address of the port to
which the WAN link is connected. This substitution ensures that the returning response traverses the
same link.
In Figure 101 - WAN Link Load Balancing for Outbound Traffic, page
1.1.1.2 sends an HTTP request to the Internet. Outbound traffic from client 1 reaches port 5 on the
Alteon which is configured with a redirection filter for link load balancing. The traffic is load balanced
between ports 2 and 7 depending on the metric of the WAN group (configured as real servers 1 and
2).
Document ID: RDWR-ALOS-V2900_AG1302
Alteon Application Switch Operating System Application Guide
633.
634.
WAN Link Load Balancing
634, client 1 at IP address
633