Network Load Balancing Services
Encyclopedia
Network Load Balancing Services (NLBS) is a Microsoft
implementation of clustering and load balancing
that is intended to provide high availability and high reliability, as well as high scalability. NLBS is intended for applications with relatively small data sets that rarely change (one example would be web pages), and do not have long-running-in-memory states. These types of applications are called stateless applications, and typically include Web, File Transfer Protocol
(FTP), and virtual private network
ing (VPN) servers. Every client request to a stateless application is a separate transaction, so it is possible to distribute the requests among multiple servers to balance the load.
One attractive feature of NLBS is that all servers in a cluster monitor each other with a heartbeat signal, so there is no single point of failure.
In its current incarnation in Windows Server 2003
, NLBS does not support automatic removal of a failed server from a cluster unless the server is completely offline, or if its NLBS service is stopped. For example, if a web server is returning an error page instead of correct content, it is still perceived as "alive" by NLBS. As such, a monitoring script is typically required on every participating node, which checks the correctness of local web page delivery, and calls the nlb.exe utility to add or remove itself from the cluster as needed.
Configuration Tips:
.
Auto fail over is also a part in this frame.
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
implementation of clustering and load balancing
Load balancing (computing)
Load balancing is a computer networking methodology to distribute workload across multiple computers or a computer cluster, network links, central processing units, disk drives, or other resources, to achieve optimal resource utilization, maximize throughput, minimize response time, and avoid...
that is intended to provide high availability and high reliability, as well as high scalability. NLBS is intended for applications with relatively small data sets that rarely change (one example would be web pages), and do not have long-running-in-memory states. These types of applications are called stateless applications, and typically include Web, File Transfer Protocol
File Transfer Protocol
File Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
(FTP), and virtual private network
Virtual private network
A virtual private network is a network that uses primarily public telecommunication infrastructure, such as the Internet, to provide remote offices or traveling users access to a central organizational network....
ing (VPN) servers. Every client request to a stateless application is a separate transaction, so it is possible to distribute the requests among multiple servers to balance the load.
One attractive feature of NLBS is that all servers in a cluster monitor each other with a heartbeat signal, so there is no single point of failure.
In its current incarnation in Windows Server 2003
Windows Server 2003
Windows Server 2003 is a server operating system produced by Microsoft, introduced on 24 April 2003. An updated version, Windows Server 2003 R2, was released to manufacturing on 6 December 2005...
, NLBS does not support automatic removal of a failed server from a cluster unless the server is completely offline, or if its NLBS service is stopped. For example, if a web server is returning an error page instead of correct content, it is still perceived as "alive" by NLBS. As such, a monitoring script is typically required on every participating node, which checks the correctness of local web page delivery, and calls the nlb.exe utility to add or remove itself from the cluster as needed.
Configuration Tips:
- The network load balancing service requires for all the machines to have the correct local time. Ensure the Windows Time Service is properly configured on all hosts to keep clocks synchronized. Unsyncronized times will cause a network login screen to pop up which doesn't accept valid login credentials.
- The server console can't have any network card dialogue boxes open when you are configuring the "Network Load Balancing Manager" from your client machine.
- You have to manually add each load balancing server individually to the load balancing cluster after you've created a cluster host.
- To allow communication between servers in the same NLB cluster, each server requires the following registry entry: a DWORD key named "UnicastInterHostCommSupport" and set to 1, for each network interface card's GUID (HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\WLBS\Parameters\Interface\{GUID})
- NLBS may conflict with some Cisco routers, which are not able to resolve the IP address of the server and must be configured with a static ARP entry.
History
Windows NT Load Balancing Service (WLBS) is a feature of Windows NT that provides load balancing and clustering for applications. WLBS dynamically distributes IP traffic across multiple cluster nodes, and provides automatic failover in the event of node failure. WLBS was replaced by Network Load Balancing Services in Windows 2000Windows 2000
Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...
.
Auto fail over is also a part in this frame.