NLB Introduced with Windows 2000 AS / DC Scalibility for TCP/IP based services (e.g. IIS, Web Services, streaming media, terminal services etc.) Up to 32 PCs can be in a NLB'ed cluster Detects failure of a server and reroutes within 10 seconds Provides clients with a common virtual IP address that represents all the NLB'ed servers MS doc @ +ve: Does NOT use a central dispatcher, making it superior to most round-robin solutions Does NOT require mirrored or special hardware Each PC can also be given a decidated IP address which is never load balanced (so we can, for example, remotely admin a specific machine) Each PC in the cluster is given an unique Host Priority value (1-32). The PC with the lower number has the highest priority and is made the default host. A set of virtual IP addresses can be set up for the virtual host to ensure that applications that cannot handle load balancing (for example, ones that require state) go to the same (single) server each time. Note that all requests to these IP addresses go to the same machine and are not round robined. The advantage here is that should the default host expire, traffic will be routed to the PC with the next lowest Host Priority automatically. Port Rules: Allow all the traffic for a particular set of ports to be routed to one particular PC with the highest Handling Priority for that port (similar to above, if the PC with the highest HP fails the traffic is subsequently routed to the PC with the next highest HP) Allows all the traffice for a partucalar set of ports to be routed to one PC from a set of multiple PCs, the ratio of traffic being sent to each PC being user-definable (in case you have a cray and a 386 in the same cluster) Client Affinity: Clustering Failover support (database, messaging, file services, print services etc.)