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→An Overview of Network Load Balancing Clusters
Network Load balancing provides failover and high scalability for Internet Protocol (IP) based services providing support for Transmission Control Protocol (TCP), User Datagram Protocol (UDP) and general Routing Encapsulation (GRE) traffic. Each server in a cluster is referred to as a ''node''. Network Load Balance Clustering is supported by all versions of Windows Server 2008 with support for clusters containing 2 up to a maximum of 32 nodes.
Network Load Balancing assigns a virtual IP address to the cluster. When a client request arrives at the cluster this virtual IP address is mapped to the real address of a specific node in the cluster based on configuration settings and server availability. When a server fails, traffic is diverted to another server in the cluster. When the failed node is brought back online it is then re-assigned a share of the load. From a user perspective the load balanced cluster appears to to all intents and purposes as a single server represented by the one or more virtual Ip addressIP addresses.
The failure of a node in a cluster is detected by the transmission of ''heartbeats'' by each node. If a node fails to transmit a heartbeat for a designated period of time that node is assumed to have failed and the remaining nodes takeover the work load of the failed server.
