 <p>When you use port 636, LDAP over SSL is used,</p> <p><a href="http://en.wikipedia.org/wiki/Ldap" rel="nofollow">http://en.wikipedia.org/wiki/Ldap</a></p> <p>If you use Microsoft Network Monitor or Wireshark to capture the packets, you may gain more insights on packet level.</p> <p>In this case, CRL is necessary as it is enabled by default. But you can turn it off on machine or application level,</p> <p><a href="http://www.page-house.com/blog/2009/04/how-to-disable-crl-checking.html" rel="nofollow">http://www.page-house.com/blog/2009/04/how-to-disable-crl-checking.html</a></p>