title: Http - use of "upgrade" header value
body: <p>I know that websockets (Html5) uses upgrade header to let the server know that the session would be using same port (80) but a different protocol.</p>
  
  <p>Are there any other elements (be it in HTML5 or others) that use "upgrade". I need to find something online that uses "upgrade" in order to test some behavior.</p>