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Spirent TestCenter : The right "fragment offset" value to use when we send fragment with raw streamblock

Environment/Versions
  • Spirent TestCenter
  • IP Fragmentation using Raw streamblocks
Answer

 When trying to send fragment packets, the "fragment offset" value should be right, or else DUT or wireshark can't reassemble the packets.

The unit of "Fragment offset" is 8 bytes.

So if the frame length of each fragment is 1514(without FCS), the data length in the IP packet is 1514 - 14(Ethernet Header) - 20(IP Header) =1480

"Fragment offset" of the second fragment should be 1480/8 = 185

So the value of "Fragment offset" be set in the STC should be 185 (For second fragment), 370(For the third fragment) and so on

Note :  All fragments must have the same Identification field value in the IP Header.


Product : Spirent TestCenter,Spirent TestCenter,IP,PGA