I was recently looking a for some information on Microsoft's Network Load Balancing Service on Windows 2003 and the implications on the use of SSL. Whilst Microsoft's TechNet documentation is comprehensive (http://technet.microsoft.com/en-us/library/cc738224%28WS.10%29.aspx), it does not provide the succinct overview that I required.
I found that Rick Strahl's article and walkthrough of the setup extremely useful (http://www.west-wind.com/presentations/loadbalancing/NetworkLoadBalancingWindows2003.asp). Rick describes setting up single affinity port rules for HTTPS, but there is little discussion of the feasability and implications of load balancing HTTPS requests.
Précising information gleaned from TechNet: SSL authenticated data uses client session state that is maintained across TCP connections. Whilst successive HTTPS requests can be load balanced, as the session state is automatically recreated on each server by re-authenticatiing the client, this is expensive. Single affinity is recommended.
From Microsoft's documentation:
Applications that use SSL with Single affinity are efficient because the SSL session IDs are reused. Negotiating a new SSL session ID requires five times the amount of overhead as reusing a SSL session ID. Although negotiating the SSL session ID is transparent to the client, the cumulative increase in overhead could degrade the performance of the cluster.
http://technet.microsoft.com/en-us/library/cc759039%28WS.10%29.aspx