title: Why do we say the IP protocol in TCP/IP suite is connectionless?
body: <p>Why is the IP called a connectionless protocol? If so, what is the connection-oriented protocol then?</p>
  
  <p>Thanks.</p>
  
  <p>Update - 1 - 20:21 2010/12/26</p>
  
  <p>I think, to better answer my question, it would be better to explain what "connection" actually means, both physically and logically.</p>
  
  <p>Update - 2 - 9:59 AM 2/1/2013</p>
  
  <p>Based on all the answers below, I come to the feeling that the 'connection' mentioned here should be considered as a set of actions/arrangements/disciplines. Thus it's more an abstract concept rather than a concrete object.</p>
  
  <p>Update - 3 - 11:35 AM 6/18/2015</p>
  
  <p>Here's a more physical explanation:</p>
  
  <ul>
  <li><p>IP protocol is connectionless in that all packets in IP network are routed independently, they may not necessarily go through the same route, while in a virtual circuit network which is connection oriented, all packets go through the same route. This single route is what 'virtual circuit' means.</p></li>
  <li><p>With connection, because there's only 1 route, all data packets will arrive in the same order as they are sent out.</p></li>
  <li><p>Without connection, it is not guaranteed all data packets will arrive
  in the same order as they are sent out.</p></li>
  </ul>
  
  <p>Update - 4 - 9:55 AM 2016/1/20/Wed</p>
  
  <p>One of the characteristics of <code>connection-oriented</code> is that the packet order is preserved. TCP use a sequence number to achieve that but IP has no such facility. Thus TCP is connection-oriented while IP is connection-less.</p>