title: difference between ${CDR(duration)} and ${CDR(billsec)} in asterisk dialplan
body: <p>I want to get the duration of the call but confused which variable to use</p>
  
  <p><strong>${CDR(duration)}</strong>  or</p>
  
  <p><strong>${CDR(billsec)}</strong></p>
  
  <p><a href="https://wiki.asterisk.org/wiki/display/AST/CDR+Variables" rel="nofollow noreferrer">Here</a> it is not clear from when ${CDR(duration)}  records the time</p>
  
  <p><strong>So which should i use ${CDR(duration)} or ${CDR(billsec)} ?</strong></p>