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Network Load Balancing

Network Load Balancing is often used in Windows 2000 Advanced Server and DataCenter clusters to distributes IP traffic to multiple copies (or instances) of a TCP/IP service across multiple servers within the cluster. As traffic increases, additional servers can be added to the cluster, with up to 32 servers possible in any one cluster. From the client©s point of view, the cluster appears to be a single server that answers these client requests. NLB also provides high availability by automatically detecting the failure of a server and repartitioning client traffic among the remaining servers within ten seconds.

Where to Start
Microsoft's Load-Balancing Services
Microsoft's Load-Balancing Services In 1998, Microsoft acquired Windows NT Load Balancing Service (WLBS) from Valence Research. This product, which Valence marketed as Convoy Cluster, is a free add-on service to Windows NT Server, Enterprise Edition (NTS/E). Microsoft implemented this service in Windows 2000 Advanced Server (Win2K AS) and Windows 2000 Datacenter Server (Datacenter) as Network Load Balancing (NLB) service. Administrators most commonly use WLBS and NLB to distribute Web .Source: Windows & .NET Magazine (April 2000)

Network Load Balancing - A technical overview
Network Load Balancing, a clustering technology included in the Windows© 2000 Advanced Server and Datacenter Server operating systems, enhances the scalability and availability of mission-critical, TCP/IP-based services, such as Web, Terminal Services, virtual private networking, and streaming media servers. The unique and fully distributed architecture of Network Load Balancing enables it to deliver very high performance and failover protection, especially in comparison with dispatcher-based load balancers. This white paper describes the key features of this technology and explores its internal architecture and performance characteristics in detail. Source: Microsoft TechNet CD Online (updated June 22, 2000)

Network Load Balancing in Windows 2000 Advanced Server and DataCenter Server
With Network Load Balancing (NLB), Windows 2000 Advanced Server enables organizations to cluster up to 32 servers, evenly distributing incoming traffic, scaling performance to mirror demand, and automatically switching to another server in the event of failure.

Network Load Balancing Hotfix Package
Microsoft Knowledge Base Article: 278670 - Several Network Load Balancing hotfixes that were published before February 1, 2001, replace one or more Network Load Balancing .dll files and cannot be applied simultaneously. The hotfix package that is described in this article provides a set of Network Load Balancing .dll files that contain the hotfixes that were published before February 1, 2001

Post-Windows 2000 SP1 Hotfix for Network Load Balancing
Microsoft Knowledge Base Article: 270635 - As a convenience, Microsoft has combined the following post-Windows 2000 Service Pack 1 (SP1) hotfixes into one self-installing package that you can install on a Windows 2000-based computer that is running Network Load Balancing.

Technical Articles

Configuring Network Load Balancing
Microsoft Knowledge Base ArticleQ240997 - This article describes how to enable and configure Network Load Balancing (NLB) in Windows 2000 Advanced Server or Datacenter Server. 

Description of Network Load Balancing Features
Microsoft Knowledge Base ArticleQ232190 - This article describes the Network Load Balancing (NLB) features.

How to Configure an IP Address for NLB with One Network Adapter
Microsoft Knowledge Base Article: 256124 - This article describes how to properly configure IP addresses with Network Load Balancing. 

HOW TO: Configure Network Load Balancing Parameters in Windows 2000 
Microsoft Knowledge Base Article: 303608 - This step-by-step guide describes how to configure Network Load Balancing (NLB) parameters.

How to Configure Network Load Balancing Web Services with Back-End SQL Server
Microsoft Knowledge Base Article: 268317 - This article describes how to configure Network Load Balancing Web services with a back-end SQL server. (updated 7/30/2001) 

HOW TO: Install Network Load Balancing if Previously Uninstalled 
Microsoft Knowledge Base Article: 303751 - This step-by-step guide describes how to install Network Load Balancing (NLB) if it has been uninstalled. 

HOW TO: Set Up TCP/IP for Network Load Balancing 
Microsoft Knowledge Base Article: 303817 - This article describes how to set up Transmission Control Protocol/Internet Protocol (TCP/IP) for Network Load Balancing, which is typically the last step of a Network Load Balancing installation. 

How WLBS Handles the Dedicated IP Address
Microsoft Knowledge Base Article: 233279 - The dedicated Internet Protocol (IP) address you configure during Windows NT Load Balancing Service (WLBS) or Windows 2000 Network Load Balancing (NLB) Setup is the local host's unique IP address used for dedicated traffic to the host or network traffic not associated with the cluster. The WLBS or NLB driver passes all packets addressed to the dedicated IP to the TCP/IP stack. 

IP Address Assignment for NLB with Multiple Network Adapters
Microsoft Knowledge Base Article: 256910 - This article describes how to properly configure IP addresses with Network Load Balancing (NLB).

Monitoring Modules and Windows 2000 Network Load Balancing Service
Monitoring Modules and Windows 2000 Network Load Balancing Service The Microsoft Win2K Network Load Balancing (NLB) service permits multiple servers in a cluster to act as one virtual server. When a request comes to the virtual NIC©s IP address, NLB determines which server is the least busy and sends the request to that server. For example, suppose that I cluster Server One and Server Two as the Web servers for the mycompany.com Web site and use NLB to load balance the servers.
Source: Windows & .NET Magazine (July 1, 2000)

Performance Enhancements for Network Load Balancing
Microsoft Knowledge Base Article  Q255014 - Network Load Balancing, in some circumstances, may not manage client connections efficiently and may cause an unnecessary drain on system resources.

Using Terminal Server with Windows Load Balancing Service
Microsoft Knowledge Base Article: 243523 - This article describes how to use Windows Load Balancing Service (WLBS) or Network Load Balancing (NLB) in Windows Terminal Server.

Windows 2000 Interoperability Between MSCS and NLB
Microsoft Knowledge Base Article: 235305 - Network Load Balancing (NLB) has the same feature set as Windows Load Balancing Service (WLBS) in Microsoft Windows NT 4.0. It provides the ability to distribute network client load across up to 32 nodes in a cluster.

Troubleshooting, Known Issues and Bugs:
Cannot Use Wlbs.exe Remote Control Commands From Load Balanced VPN Servers
Microsoft Knowledge Base Article: 269004 - If you use the Wlbs.exe command line to remotely control a Network Load Balancing (NLB) cluster node that is part of an NLB cluster that is load balancing Point-to-Point Tunneling Protocol (PPTP) services, you may receive the following error message

L2TP Sessions Lost When Adding a Server to an NLB Cluster
Microsoft Knowledge Base Article: 248346 - When you are using Network Load Balancing (NLB) to load-balance a cluster of Layer 2 Tunneling Protocol (L2TP) servers, clients experience broken L2TP sessions when a server is added to the cluster.

Network Load Balancing Connection to a Virtual IP Address Not Made Across a Switch
Microsoft Knowledge Base Article: 247297 - When you attempt to establish a connection to the virtual IP address of a Network Load Balancing (NLB) cluster, the connection cannot be made across a switch. When the cluster is connected to a hub with a client, the client is able to make a connection without a problem.

Network Load Balancing Component Calls Itself WLBS
Microsoft Knowledge Base Article: 221971 - When you are using the command interface or accessing information in Event Viewer, the Network Load Balancing (NLB) component is called WLBS.

Network Load Balancing Does Not Have a Virtual Network Adapter
Microsoft Knowledge Base Article: 240993 - Microsoft Windows NT Load Balancing Service (WLBS) in Microsoft Windows NT 4.0 creates a "WLBS Virtual NIC" entry on the on the Adapters tab in the Network tool in Control Panel.

Network Load Balancing May Stop in Unicast Mode with Some FDDI Network Adapters
Microsoft Knowledge Base Article: 254110 - Describes why Network Load Balancing (NLB) in unicast mode may not work with all Fiber Distributed Data Interface (FDDI) network adapters.

Network Load Balancing Cluster no Longer Responds to Simple Network Management Protocol Requests
Microsoft Knowledge Base Article: 280307 - Under the following conditions, when all hosts in an Network Load Balancing (NLB) cluster are stopped and then started again, the cluster no longer responds to Simple Network Management Protocol (SNMP) requests:

Network Load Balancing Temporarily Fails in a Switched Environment
Microsoft Knowledge Base Article: 261957 - When you use Network Load Balancing (NLB) with a Layer 2 switch, load balancing clients may experience a brief, temporary disruption of service when a new NLB server is added to, or an "old" server is removed from the cluster.

Network Load Balancing Temporarily Fails in a Switched Environment

Microsoft Knowledge Base Article: 261957 - When you use Network Load Balancing (NLB) with a Layer 2 switch, load balancing clients may experience a brief, temporary disruption of service when a new NLB server is added to, or an "old" server is removed from the cluster. 

Network Load Balancing WMI Provider Memory Leak
Microsoft Knowledge Base Article: 266375 - The Network Load Balancing (NLB) Windows Management Instrumentation (WMI) provider leaks significant amounts of memory in the Winmgmt process. In testing scenarios, the leak has been as much as 20 MB in 10 hours.
 

"NLB Failed to Start" Error Message If NLB Is Not Installed
Microsoft Knowledge Base Article: 268437 - The following error message may be placed in the System log during startup: Event ID: 7000 Event Source: Service Control Manager Description: The Network Load Balancing service failed to start due to the following error: The service cannot be started, either because it is disabled or because it has no enabled devices associated with it. Network Load Balancing is not installed on the system. Cause: Although Network Load Balancing (NLB) is not currently installed, some NLB registry keys may be present in the registry.

NLB Operations Affect All Network Adapters on the Server
Microsoft Knowledge Base Article: 222079 -  Certain network load balancing (NLB) operations affect all network adapters detected on the computer.

"Proxy Chain Loop" Error Message Using Proxy Server and NLB
Microsoft Knowledge Base Article: 269165 - After you install Network Load Balancing (NLB) with Proxy Server 2.0, you may receive the following error message in your browser: 

WLBS Does Not Detect Program or Service Problems
Microsoft Knowledge Base Article: 234151 - Windows NT Load Balancing Service (WLBS) and Windows 2000 Network Load Balancing (NLB) doe not provide failover at the service, program, or port level because both WLBS and NLB are TCP/IP load balancers and are not designed to detect when a program or service is not working correctly.

Using Crossover Cable Causes Load Balancing Not to Work
Microsoft Knowledge Base Article: 242248 - Although cluster nodes may be able to ping each other, other devices on the same subnet may not be able to ping the cluster IP address, or may not be able to gain access to TCP services configured for load balancing.

Using the "WLBS QUERY" Command to Determine the State of an WLBS/NLB Cluster
Microsoft Knowledge Base Article: 242242 - The wlbs query command displays the current state of a Windows Load Balancing Service (WLBS)/Network Load Balancing (NLB) cluster. Additionally, it provides host priority information.


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