10Installing 3Com Advanced Server Features for Windows

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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