Every day this week the Clustering & High-Availability is writing about some of the top questions we get about Network Load Balancing (NLB) in Windows Server 2008 R2. We hope you find these helpful!
Software Test Engineer
Network Load Balancing
Which applications work with NLB?
Since NLB works at the TCP/IP layer, in theory it can work with any TCP or UDP based application. However, depending on the application’s requirement to maintain state or consistency of data, some work better with NLB than others. Examples of common applications that work well with NLB include: HTTP & HTTPS (web traffic), FTP (file downloads), POP3/SMTP (email), Terminal Services, and Streaming Media.
Other services such as VPN, NAT and IPv6 technologies can also be load balanced. It is recommended that NLB be configured to use Bi-Directional Affinity (BDA) for these scenarios. For these scenarios it is recommended to use ISA or DirectAccess for configuring BDA. More information about BDA is available here: http://technet.microsoft.com/en-us/library/dd364013(WS.10).aspx.
Does NLB provide performance-based load balancing?
No, not directly. NLB uses a hash algorithm to determine which host a request should be serviced by. While NLB can facilitate performance-based load balancing, other solutions are required to orchestrate it.
For example, some people scale-up or scale-down the number of nodes to meet their needs, or they need to change the Load Weight of the port rule to allow some nodes to handle less traffic than others. This is accomplished by creating a monitoring application that monitors traffic on each node and then takes the appropriate action by automatically changing the Load Weight for a port rule.