How to calculate Round Trip Time in Ping utility implementation in UnetStack

Question

I had developed ping utility similar to the ping example available in UnetStack1.3 (/samples/ping) to ping a remote node over a multi-hop link, but unable to calculate the Round Trip Time (RTT), when I transmit ping packet using routing agent with static route information added to routing table using RouteDiscoveryNtf as there is no timing information avaiable in upper layer notifications (DatagramNtf or DatagramDeliveryNtf or DatagramFailureNtf).

Calculation of round trip time is the difference of rxtime and txtime available with TxFrameNtf and RxFrameNtf as implemented in clousure (fshrc.groovy) in the ping example.

I also tried analyzing the ping utility implemented in UnetStack3, but unable to makeout. Please let me know how the RTT is calculated.

Answer 1

Here's a simplified version of the implementation of the ping command in UnetStack3:

  def ping(int n, int m = 3, long timeout = 30000) {
    println "PING $n"
    AgentID router = agentForService(Services.ROUTING)
    int p = 0
    m.times { count ->
      def t0 = currentTimeMillis()
      router << new DatagramReq(to: n, reliability: true)
      def ntf = receive({
        it instanceof DatagramDeliveryNtf || it instanceof DatagramFailureNtf
      }, timeout)
      def t = currentTimeMillis()-t0
      if (ntf == null || ntf instanceof DatagramFailureNtf) {
        println "Request timeout for seq $count"
      } else {
        p++
        println "Response from $n: seq=$count rthops=2 time=$t ms"
      }
      delay(5000)
    }
    println "$m packets transmitted, $p packets received, ${Math.round(100*(m-p)/m)}% packet loss"
  }