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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 Gb/s = 1 bit time = 1/1,000,000,000 or 1nS 

 complete packet = 60 data bytes + 4 CRC bytes = 64 bytes

 
64 bytes * 8bits/byte = 512 bits
 
512 bits + 64 bits preamble = 576 bit/time
 
time to send complete packet = 576 bit/time * 1nS/bit = 576 nS/packet
                                                          packet
 
packet + min. gap = 576nS + 96nS min. gap (12 byte 100% load) = 672nS (packet + min. gap)
 
# of packets sent in a second using min. gap (wire speed) = 1sec./672nS = 1488095 packet/sec.
 
50% utilization = 1488095 packets * .5 @ 744047 packets/sec
 
Data Traffic time on wire per second - 744047 * 576 nS/packet = 428571072 nS
 
1,000,000,000 nS (1 sec) – 428571072 nS
 
Total gap on wire per second = 571428928 nS
 
571428928 nS/ 744047 packets/sec = 768 nS gap per packet
 
x bits/768 nS gap per packet = 1bit/1 nS = 768 and 768/8 = 96 byte IFG
 
packet + min. gap = 576nS + 768nS min. gap = 1344 nS (packet + min. gap)
 

10 Gigabit example:

10000 Mb/s = 1 bit time = 1/10,000,000,000 or 0.1nS

 complete packet = 1496 data bytes
 
1496 bytes * 8bits/byte = 11968 bits
 
512 bits + 64 bits preamble = 12032 bit/time
 
time to send complete packet = 12032 bit/time * 0.1 nS/bit = 1203.2 nS/packet
                                                              packet
 
packet + min. gap = 1203.2 nS + 9.6 nS min. gap (12 byte 100% load) = 1212.6 nS (packet + min. gap)
 
# of packets sent in a second 9.6 ns. gap (> wire speed) = 1sec./ 1212.6 nS = 824674 packet/sec
 
824674 packet/sec * 0.91 = 750453 packet/sec
 
Data Traffic time on wire per second - 750453 * 1203.2 nS/packet = 902945736 nS
 
1,000,000,000 nS (1 sec) – 902945736 nS
 
Total gap on wire per second = 97054264 nS
 
97054264 nS/ 750453 packets/sec = 129.3 nS gap per packet
 
x bits/129.3 nS = 1 bit/0.1 nS = 1293 and  1293/8 = 162 bytes
 
packet + gap = 1203.2 nS + 129.3 nS gap = 1332 nS (packet + gap)
 

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

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