title: how to get packet loss and delay of a link in Ryu
body: <p>To specify a path by minimum cost for sending a flow, I want to calculate the cost of link in Ryu controller by the following equation:</p>
  
  <p>cost(e)=delay(e) + PL(e)      ∀ e ε E</p>
  
  <p>delay(e) is delay of link e. PL(e) is packet loss of link e.
  How to get delay and packet loss of a link in realtime using Ryu and OpenFlow?</p>
  
  <p>Thanks.</p>