rom all their devices at full line speed. CCS sends acknowledgements or failure notifications (in the form of special ACK and NACK JSON-encoded XMPP messages) asynchronously.</li>
    </ul>
  </li>

  <li>JSON
    <ul>
      <li>GCM HTTP: JSON messages sent as HTTP POST.</li>
      <li>CCS: JSON messages encapsulated in XMPP messages.</li>
    </ul>
  </li>
</ul>
<p>This document describes how to use CCS. For general concepts and information on how to use GCM HTTP, see the <a href="gcm.html">GCM Architectur