title: Firefox HTTP connections spend a lot of time on blocking phase
body: <p>My application is performing a lot of consecutive XHR calls. This means establishing a lot of HTTP connections.</p>
  
  <p>I'm trying to analyze the performance of all these connections. I found out that the first HTTP connection made spends about 10% of its duration on <em>Blocking</em> (following definition quoted from <a href="http://getfirebug.com/wiki/index.php/Net_Panel#Request_Timeline" rel="nofollow" title="Firebug Wiki">Firebug Wiki</a>):</p>
  
  <blockquote>
    <p><strong>Blocking</strong> - <em>Time spent in a browser queue waiting for a network connection (formerly called Queueing). For SSL connections this includes the SSL Handshake and the OCSP validation step.</em></p>
  </blockquote>
  
  <p>In consecutive calls, the time spent on blocking increases, and after about 10 calls, the blocking holds steady at an average of ~120MS (!!!).</p>
  
  <p>I've tried to measure the HTTP connections similarly in Chrome with the DevTools and in IE with Fiddler, and though they don't use the exact same stages/names for the different stages on an HTTP connection, neither shows signs of the inordinate amount of time spent on blocking that Firefox does.</p>
  
  <p>I can exclude that it's a lack of available (persistent) HTTP connections. Since the XHR calls are done synchronously.</p>
  
  <p>Anyone familiar with this Firefox behaviour? If necessary, I can show the Firebug Net Panel output.</p>