
10 Installing 3Com Advanced Server Features for Windows
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Load Balancing
Load balancing maximizes bandwidth at the server through the use of multiple parallel
resilient server links (RSLs) that share the network load as shown in the next figure.
An RSL consists of two or more NICs that form a virtual NIC. Each virtual NIC has multiple
physical NICs bound to it, forming a group. Each NIC in a group uses the same protocols
and frame types. One NIC is designated the primary NIC and the others secondary NICs.
Failover
In addition to load balancing, RSLs provide failover fault tolerance between a server and a
switch—if one NIC in a group fails, the others assume the network load of the failed NIC.
The failover behavior of secondary NICs depends on how you set load balancing:
• In a transmit load balancing arrangement, the primary NIC is the only one that
receives packets. If the primary NIC fails, a secondary NIC assumes the configuration
profile, network traffic, and active status of the failed primary NIC.
• In a bidirectional load balancing arrangement, all NICs receive packets. If any NIC fails,
receive load balancing is disabled, and the other NICs continue transmit-only load
balancing activity. Receive load balancing is restored when new connections are
established with clients.
If the primary NIC fails, a secondary NIC takes over packet reception for the group.
Bidirectional load balancing is restored after a failure when applications create new
connections and new clients log in as illustrated in the following figure.
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