title: What are all the fields in a Python ntplib response, and how are they used?
body: <p>I'd like to make a measurement of the difference between a local clock, and 
  a remote processor running an NTP server. </p>
  
  <p>I can get the tx_time of the response, as shown below, but a better estimate would include some estimate of the network delays.  There are other fields in the NTP response message which should be used, as well.</p>
  
  <pre><code>import ntplib
  from time import ctime,time
  
  addr_remote = '128.128.204.207'
  
  c = ntplib.NTPClient()
  remote = c.request(addr_remote)
  local = time()
  print("REMOTE: " + ctime(remote.tx_time) + "   &lt;reference clock&gt;   ") 
  print("LOCAL:  " + ctime(local)        + "   delta: " + str(local - remote.tx_time ))
  </code></pre>
  
  <p>If I look at "remote": </p>
  
  <pre><code>for attr in dir(remote):
      print("remote.%s = %r" % (attr, getattr(remote, attr)))
  </code></pre>
  
  <p>I see:</p>
  
  <pre><code>remote.delay = 0.0
  remote.dest_time = 1531863145.9309998
  remote.dest_timestamp = 3740851945.9309998
  remote.from_data = &lt;bound method NTPPacket.from_data of &lt;ntplib.NTPStats object at 0x000000000265B2E8&gt;&gt;
  remote.leap = 0
  remote.mode = 4
  remote.offset = -1.8789582252502441
  remote.orig_time = 1531863145.9309998
  remote.orig_timestamp = 3740851945.9309998
  remote.poll = 0
  remote.precision = -7
  remote.recv_time = 1531863144.0520415
  remote.recv_timestamp = 3740851944.0520415
  remote.ref_id = 0
  remote.ref_time = 0.0
  remote.ref_timestamp = 2208988800.0
  remote.root_delay = 0.0
  remote.root_dispersion = 0.0
  remote.stratum = 9
  remote.to_data = &lt;bound method NTPPacket.to_data of &lt;ntplib.NTPStats object at 0x000000000265B2E8&gt;&gt;
  remote.tx_time = 1531863144.0520415
  remote.tx_timestamp = 3740851944.0520415
  </code></pre>
  
  <p>So, how do I use these: </p>
  
  <ul>
  <li><strong>dest_time</strong></li>
  <li><strong>orig_time</strong></li>
  <li><strong>recv_time</strong></li>
  <li><strong>tx_time</strong> </li>
  </ul>
  
  <p>to remove the network delays, and get a better estimate of the clock difference?</p>