IIS TIPS - Network Load Balancing
From Microsoft ...
a) What's NLB ?
Network Load Balancing is a clustering technology offered by Microsoft as part of all Windows 2000 Server and Windows Server 2003 family operating systems. NLB uses a distributed algorithm to load balance network traffic across a number of hosts, helping to enhance the scalability and availability of mission critical, IP-based services, such as Web, Virtual Private Networking, Streaming Media, Terminal Services, Proxy, etc. It also provides high availability by detecting host failures and automatically redistributing traffic to operational hosts.
b) Cluster and NLB difference ?
A server cluster (MSCS) is a collection of servers that together provide a single, highly available platform for hosting applications. Applications can be failed over to ensure high availability in the event of planned downtime due to maintenance or unplanned downtime due to hardware, Operating System or application failures. Server clusters provide a highly available platform for applications such as SQL Server, Exchange Server data stores, file and print servers, etc. Server clusters are used for stateful applications that rely on some state context from one request to the next.
Network Load Balancing (NLB) clusters dynamically distribute the flow of incoming TCP and UDP traffic among the cluster nodes according to a set of traffic-handling rules. NLB clusters provide a highly available and scalable platform for applications such as IIS, ISA server, etc. NLB is used for stateless applications; i.e. those that do not build any state as a result of a request.
NLB and server clusters compliment each other in complex architectures: NLB is used for load balancing requests between front-end web servers while server clusters provide high availability for backend database access.
c) Can I mix NT4.0 WLBS, W2K WLBS and W2K3 NLB together ?
Yes, mixing Windows NT 4.0 WLBS, Windows 2000 NLB and Windows Server 2003 is supported. There is no additional work needed and the heartbeat packets from NLB in Windows Server 2003 are backward compatible with WLBS on Windows NT 4.0 and Windows 2000 NLB. However, you can't utilize new features offered by W2K3 NLB.
Click here for complete Microsoft NLB FAQ.