Network Load Balancing on Windows Server 2003 2

[Grovie]

How does NLB load balance in laymans terms?
Will you continue to use the same node when you use subesquent pages?
Will you go back to the same node the next time you log onto the web application? what happens if this node is unavailable - will it fail to a working one automatically.
What happens if a node you are working through becomes unavailable whilst using it, will it fail to an available node.
What will happen if you change nodes mid way through using a web based application that requires authentication?
Thanks
Lucy

 

[NickFerrar]

1). All nodes use a common algorithm to determine if they should pickup the next request. They heartbeat to determine if a node has failed and therefore if the algorithm needs to change, there is no dedicated heartbeat network though like in a server cluster.

2). It depends on whether or not and how you'd configured affinity. I think the default is no affinity in which case any node could pick up requests.

3). Again this depends on affinity.

4). Subsequent requests should go to other nodes (assuming convergence has occured). However SSL sessions may break and need to be re-established.

5). In theory it's supposed to re-establish SSL connections but I've encountered issues with this in practice. I think MS broke something in IE6 with a security hotfix - they've corrected this within IIS but you have to find another workaround if you're using a different web-server.

Best thing to do is trawl the MS web-site for docs such as:

http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/clustering/default.mspx

 

[Grovie]

How does using affinity ensure that the same node is used - how does it recognise the user?
Thanks

 

[tfg13]

Good explanation NickFerrar. Star for you!!!!

 

[NickFerrar]

Affinity works either on the source IP or by the source class-C network (depending on which affinity mode you select). You'd usually just go with single affinity (based on source IP address) unless you're dealing with complex proxy server scenarios.