[ns] Jitter Calculation

[Mohammad Haseeb Zafar]

Hello all

I wanted to know if anyone has used below awk script to calculate jitter. We 
have 2 different values of jitter, and the calculations in the script dont 
explain me fully which jitter you would look for finding out whats the jitter 
for that particular communication.
Can someone please help me for this?

Cheers

Haseeb

#  ============================== jitter.awk ============================
  BEGIN {
       num_recv=0
 }
  {
 # Trace line format: normal
 if ($2 != "-t") {
  event = $1
  time = $2
  if (event == "+" || event == "-") node_id = $3
  if (event == "r" || event == "d") node_id = $4
  flow_id = $8
  pkt_id = $12
  pkt_size = $6
  flow_t = $5
  level = "AGT"
 }
 # Trace line format: new
 if ($2 == "-t") {
  event = $1
  time = $3
  node_id = $5
  flow_id = $39
  pkt_id = $41
  pkt_size = $37
  flow_t = $45
  level = $19
 }
   # Store packets send time
 if (level == "AGT" && sendTime[pkt_id] == 0 && (event == "+" || event == "s") 
&& pkt_size >= 512) {
  sendTime[pkt_id] = time
 }
   # Store packets arrival time
 if (level == "AGT" && event == "r" && pkt_size >= 512) {
  recvTime[pkt_id] = time
  num_recv++
 }
}
  END {
 # Compute average jitter
 jitter1 = jitter2 = tmp_recv = 0
 prev_time = delay = prev_delay = processed = 0
 prev_delay = -1
 for (i=0; processed<num_recv; i++) {
  if(recvTime[i] != 0) {
          tmp_recv++
   if(prev_time != 0) {
    delay = recvTime[i] - prev_time
    e2eDelay = recvTime[i] - sendTime[i]
    if(delay < 0) delay = 0
    if(prev_delay != -1) {
     jitter1 += abs(e2eDelay - prev_e2eDelay)
     jitter2 += abs(delay-prev_delay)
    }
    prev_delay = delay
    prev_e2eDelay = e2eDelay
   }
   prev_time = recvTime[i]
  }
  processed++
 }
}
  END {
  
       printf("Jitter1 = %.2f\n",jitter1*1000/tmp_recv);
       printf("Jitter2 = %.2f\n",jitter2*1000/tmp_recv);
}
  function abs(value) {
 if (value < 0) value = 0-value
 return value
}