This article describes the Network Load Balancing (NLB) features.

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NLB features

•	Runs on the device to be load-balanced, rather than a separate device.
•	Presents a Virtual Internet Protocol (VIP) TCP/IP address to the clients.
•	Distributes incoming TCP connections and User Datagram Protocol (UDP) datagrams among up to 32 servers, scaling performance of the cluster.
•	Detects hosts that have become unavailable and automatically redistributes traffic within eight seconds, ensuring high availability.
•	Permits full remote control from any Microsoft Windows NT 4.0-based, Microsoft Windows 2000-based, or Microsoft Windows Server 2003-based computer.
•	Inherently supports Secure Sockets Layer (SSL) sessions.

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Functionality that is not included with NLB

•	Replicate data among servers. However, you can accomplish this by using Microsoft Content Replication System (CRS) or a third-party program.
•	Load-balance or provide fault tolerance to multiple database servers (unless you are using read-only databases). To do so, you can use Cluster Server.
•	Start or stop programs on the servers.
•	Detect services that are not working correctly. To do so, you can use the HTTPMon tool that is included with the Windows 2000 Resource Kit or a third-party product.
•	Globally distribute network traffic or globally load balance. To do so, you can use the round-robin feature of Domain Name System (DNS) or a third-party product.
•	Perform protocol-specific request routing or load balancing.
•	Provide a true virtual (cluster) NetBIOS computer name.
•	Page, send e-mail messages, or alert operators about a computer problem.

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.

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