title: Network: sending a video (in theory)
body: <p><strong>Context</strong></p>
  
  <ul>
  <li>We have got un unsteady transmission channel. Some packets may be lost.</li>
  <li>Sending a single network packet in any direction (from A to B or from B to A) takes 3 seconds.</li>
  <li>We allow a signal delay of 5 seconds, no more. So we have a 5-second buffer. We can use those 5 seconds however we want.</li>
  <li>Currently we use only 80% of the transmission channel, so we have 1/4 more room to utilize.</li>
  <li>The quality of the video cannot be worsened.</li>
  </ul>
  
  <p><strong>Problem</strong></p>
  
  <p>We need to make the quality better. How to handle lost packets?</p>
  
  <p><strong>Solution proposition</strong></p>
  
  <p>A certain thing - we cannot use TCP in this case, because when TCP detects some problems, it requests retransmission of lost data. That would mean that a packet would arrive after 9 seconds, which is more than the limit.</p>
  
  <p>Therefore we need to use UDP and handle those errors ourselves. How to do it then? How to make sure that not so many packets will be lost as currently, without retransmitting them?</p>