title: what's distinction of HTTP proxy, tunnel, gateway?
body: <p>all,
  I see the terms from RFC 2616.
  <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec1.html#sec1">http://www.w3.org/Protocols/rfc2616/rfc2616-sec1.html#sec1</a></p>
  
  <p>But I can't understand the distinction of the proxy, tunnel and gateway?
  Can anyone give me a simple explanation of them?</p>
  
  <p>Thanks. </p>