Fragmentation Example

IHL = 5, ID = 111, More = 0

Offset = 0W, Len = 472B

IHL=5, ID = 111, More = 1

Offset = 0W, Len = 276B

IHL=5, ID = 111, More = 0

Offset = 32W, Len = 216B

MTU = 1500B

MTU = 280B

• Payload size 452 bytes needs to be transmitted

across a Ethernet (MTU=1500B) and a SLIP line (MTU=280B)

• Length = 472B, Header = 20B => Payload = 452B

• Fragments need to be multiple of 8-bytes.
  • Nearest multiple to 260 (280 -20B) is 256B
  • First fragment length = 256B + 20B = 276B.
  • Second fragment length = (452B- 256B) + 20B = 216B

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