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Spirent TestCenter: How do I calculate the frames or packets per second and interframe gap (IFG)?

Answer

I provide 1 Gigabit and 10 Gigabit example
 

  • 1 Gigabit example:
  1. 1 Gb/s = 1 bit time = 1/1,000,000,000 or 1nS 
  2. Complete packet size = 60 data bytes + 4 CRC bytes = 64 bytes
  3. Packet size in bits = 64 bytes * 8bits/byte = 512 bits
  4. 512 bits + 64 bits preamble = 576 bit/time
  5. Time to send complete packet = 576 bit/time * 1nS/bit = 576 nS/packet
  6.                                                           packet
  7. packet + min. gap = 576nS + 96nS min. gap (12 byte 100% load) = 672nS (packet + min. gap)
  8. # of packets sent in a second using min. gap (wire speed) = 1sec./672nS = 1488095 packet/sec.
  9. 50% utilization = 1488095 packets * .5 @ 744047 packets/sec
  10. Data Traffic time on wire per second - 744047 * 576 nS/packet = 428571072 nS
  • 1,000,000,000 nS (1 sec) – 428571072 nS
  1. Total gap on wire per second = 571428928 nS
  2. 571428928 nS/ 744047 packets/sec = 768 nS gap per packet
  3. x bits/768 nS gap per packet = 1bit/1 nS = 768 and 768/8 = 96 byte IFG
  4. packet + min. gap = 576nS + 768nS min. gap = 1344 nS (packet + min. gap)
 
  • 10 Gigabit example:
  1. 10000 Mb/s = 1 bit time = 1/10,000,000,000 or 0.1nS
  2.  Complete packet size= 1496 data bytes
  3. Packet size in bits = 1496 bytes * 8bits/byte = 11968 bits
  4. 512 bits + 64 bits preamble = 12032 bit/time
  5. Time to send complete packet = 12032 bit/time * 0.1 nS/bit = 1203.2 nS/packet
  6.                                                               packet
  7. packet + min. gap = 1203.2 nS + 9.6 nS min. gap (12 byte 100% load) = 1212.6 nS (packet + min. gap)
  8. # of packets sent in a second 9.6 ns. gap (> wire speed) = 1sec./ 1212.6 nS = 824674 packet/sec
  9. 824674 packet/sec * 0.91 = 750453 packet/sec
  10. Data Traffic time on wire per second - 750453 * 1203.2 nS/packet = 902945736 nS
  • 1,000,000,000 nS (1 sec) – 902945736 nS
  1. Total gap on wire per second = 97054264 nS
  2. 97054264 nS/ 750453 packets/sec = 129.3 nS gap per packet
  3. x bits/129.3 nS = 1 bit/0.1 nS = 1293 and  1293/8 = 162 bytes
  4. packet + gap = 1203.2 nS + 129.3 nS gap = 1332 nS (packet + gap)
 

enlightenedNote: please reference attached spreadsheet that provides LAN and WAN calculations

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Product : L2-3,Spirent TestCenter,PGA