title: What exactly does a HTTP or jquery $.ajax timeout mean?
body: <p>When I issue an <code>$.ajax</code> query with a <code>timeout:</code> parameter, and my <code>timeout</code> is met such that <code>error:</code> is invoked, what does that mean?</p>
  
  <p>More specifically:
   does that mean the server received the request, but is still processing it? That may mean some effect may occur, so I may have to cancel it on the server, or somehow invalidate data that was already partially written to a database.</p>
  
  <p>Or does that mean I was never able to reach the server at all? This is nice to know since then I don't have to deal with partial data on a server "save"</p>
  
  <p>Or does that mean the request made it part of the way, and now we lost track of it? In this case, I'd have to actually ask the server, "Oh hey, about that request I sent awhile ago... did you get that one? yeah? okay ignore that last save"</p>
  
  <p>OS Commands like <code>tracert</code> make it clear there  may be many servers for a TCP command to go through, so if one becomes unresponsive, it's hard to tell if it got it or not. But some protocols require an echo-back to be considered receivable (so I'm not sure if HTTP or Apache is involved in this)</p>