title: Slow performance when accessing msmdpump.dll with basic authentication. Repeated 401 observe
body: <p>I'm facing an annoying issue accessing SSAS through a HTTP/HTTPS connection using Basic Authentication.</p>
  
  <p>Everything works except if you analyse the network traffic using a sniffer, each call is emitted twice. The first one is emitted without the "Authorization" header of the http protocol which provokes a 401 error. The second one sends the request correctly filled with the "Authorization" header. This is repeated again and again for each request... ?!</p>
  
  <pre><code>Httpwatch/fiddler or IIS logs
  
  Sniffing the network calls and you will obtain:
  #    Result Protocol Host      URL                   Body    Content-Type
  1    401    HTTP    sql2008    /olap/msmdpump.dll    1293    text/html
  2    200    HTTP    sql2008    /olap/msmdpump.dll    2598    text/xml
  3    401    HTTP    sql2008    /olap/msmdpump.dll    1293    text/html
  4    200    HTTP    sql2008    /olap/msmdpump.dll     280    application/xml+xpress
  5    401    HTTP    sql2008    /olap/msmdpump.dll    1293    text/html
  6    200    HTTP    sql2008    /olap/msmdpump.dll     991    application/xml+xpress
  7    401    HTTP    sql2008    /olap/msmdpump.dll    1293    text/html
  8    200    HTTP    sql2008    /olap/msmdpump.dll    1787    application/xml+xpress
  9    401    HTTP    sql2008    /olap/msmdpump.dll    1293    text/html
  10   200    HTTP    sql2008    /olap/msmdpump.dll     197    application/xml+xpress
  </code></pre>
  
  <p>Any idea on how to bypass these recurrent authentications?</p>
  
  <p>I updated to SQLServer 2008 R2 SP1 Cumulative Patch 4 with no success. The issue seems to come from ADOMD.NET or OleDB for Olap Driver.</p>
  
  <p>Any help would be appreciated,</p>
  
  <p>Regards,
  Avinash Nigam</p>