title: WCF Identity NTLM Kerberos
body: <p>I have read numerous posts and articles about the  element in client endpoints on a WCF client but I am still a little confused. I have a client which gets SSPI errors when attempting to communicate with a net tcp WCF service. However, when I add the following into the configuration it works fine</p>
  
  <pre><code>&lt;identity&gt;
     &lt;servicePrincipalName /&gt;
  &lt;/identity&gt;
  </code></pre>
  
  <p>Now from what I have read this is telling the service to use NTLM rather than Kerberos. However, I am still not getting it. </p>
  
  <p>Does anyone have a few moments to explain this simply for me please. So, what is going on here, a little bit of background on the difference of NTLM and Kerberos, why it would work with one and not the other, why this element doesn't need a value, how to configure a service not to need it and why it is needed at all?</p>
  
  <p>Thanks</p>