http://blogs.technet.com/isablog/archive/2008/03/12/bi-directional-affinity-in-isa-server.aspxThe reason for having a network load balancing (NLB) Bi-Directional Affinity (BDA) feature in ISA Server is that it guarantees that traffic is handled in both directions by the same array server. This is very important and required if you have a Routeen-USCommunityServer 2.1 SP1 (Build: 61025.2)http://blogs.technet.com/isablog/archive/2008/03/12/bi-directional-affinity-in-isa-server.aspx#2992006Wed, 12 Mar 2008 21:15:14 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:2992006gazanga<p>I've not seen this occur, but I have wondered about this in production. &nbsp;With most enterprise-class load-balancers, there are ways to bind the session throughout the infrastructure to a particular server. &nbsp;To maintain that session affinity, is pretty crucial when you are working in tricky web-app environments. &nbsp;For example, I work with a bank whose online banking applications require session affinity to assure that one users session doesn't switch over to another users session and suddenly, user a sees user b's bank info. &nbsp;</p> <p>A very large developer of switches and routers have had a similar problem with this recently. &nbsp;Their large enterprise-class switch had two cpu's that would load-balance applications. &nbsp;However while each cpu maintained a tcp-port session and usage table, the two cpu's did not. &nbsp;Therefore, if request Alpha came in and was directed to server Bravo on cpu 1 redirecting traffic to port 5000, and then the reply came back through and hit cpu 2, then another request came in to cpu 2 and was told to hit port 5000, a tcp out of sequence error would occur and both sessions would be reset. &nbsp;It wasn't a massive outage, as it only occured every now and then. &nbsp;Session affinity can help resolve this. &nbsp;That and using ISA for load-balancing versus hardware which can't easily address these issues.</p>http://blogs.technet.com/isablog/archive/2008/03/12/bi-directional-affinity-in-isa-server.aspx#3036418Mon, 14 Apr 2008 10:48:56 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:3036418TechNet Blog CZ/SK<p>SECURITY Security Tip of the Month: Initial Considerations for Secure Deployment <a rel="nofollow" target="_new" href="http://go.microsoft.com/?linkid=8514049">http://go.microsoft.com/?linkid=8514049</a></p>