Glossary

A group of independent computers that work together to run a common set of applications and provide the image of a single system to the client and application. The computers are physically connected by cables and programmatically connected by cluster software. These connections allow computers to use problem-solving features such as failover in Server clusters and load balancing in Network Load Balancing (NLB) clusters. For details, refer to http://technet.microsoft.com/en-us/library/cc784941(WS.10).aspx.

The IP address of a NLB host used for network traffic that is not associated with the NLB cluster (for example, Telnet access to a specific host within the cluster). This IP address is used to individually address each host in the cluster and therefore is unique for each host.

Machine-participant of an NLB cluster. For details, refer to http://technet.microsoft.com/en-us/library/cc758834(WS.10).aspx.

The NLB cluster has two operating modes:

• In its default unicast mode of operation, NLB reassigns the station (MAC) address of the network adapter for which it is enabled and all cluster hosts are assigned the same MAC (media access control) address.

• In multicast mode, NLB assigns a layer 2 multicast address to the cluster adapter instead of changing the adapter's station address. For details, refer to http://technet.microsoft.com/en-us/library/cc783135(WS.10).aspx.

The NLB driver uses port rules that describe which traffic to load-balance and which traffic to ignore. By default, the NLB driver configures all ports for load balancing. You can modify the configuration of the NLB driver that determines how incoming network traffic is load-balanced on a per-port basis by creating port rules for each group of ports or individual ports as required. Each port rule configures load balancing for client requests that use the port or ports covered by the port range parameter. How you load-balance your applications is mostly defined by how you add or modify port rules, which you create on each host for any particular port range.

An IP address that is shared among the hosts of a NLB cluster. A NLB cluster may also use multiple virtual IP addresses, for example, in a cluster of multihomed Web servers. For details, refer to http://technet.microsoft.com/en-us/library/cc756878(WS.10).aspx.