http://blogs.technet.com/tristank/archive/2007/01/25/iis6-perf-tweak-for-intranets.aspxKerb authentication is performed at each request, rather than each connection. This can end up being a little top-heavy. 917557 FIX: You may experience slow performance when you use Integrated Windows authentication together with the Kerberos authenticationen-AUCommunityServer 2.1 SP1 (Build: 61025.2)