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RFC 791 / PROTOCOL MECHANISMS

Reassemble at the destination

05

Fragment offsets place data into a reassembly buffer at the destination.

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DIAGRAM§ 3.2 ↗
RFC 791 · § 3.2EXAMPLE
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Reassemble at the destinationFragment offsets place data into a reassembly buffer at the destination.DESTINATION REASSEMBLY BUFFER0–399400–799800–999800–9990–399400–799Complete data range → deliverOut-of-order fragments wait; incomplete reassembly can expire
03
Deliver only after the complete data range has arrived.

Deliver only after the complete data range has arrived.

Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
KEY POINT

Reassembly depends on identification, addresses, protocol, offsets, and the final-fragment information.

  • Reassembly depends on identification, addresses, protocol, offsets, and the final-fragment information.
  • Missing fragments can cause the incomplete reassembly to time out.
DETAILS

The drawing is a simplified worked example. Follow the linked RFC and its updates for implementation requirements.

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All chapters in this RFC
  1. Route a datagram across networks
  2. Read the IPv4 header
  3. Limit a packet’s lifetime
  4. Fragment for a smaller link
  5. Reassemble at the destination
RFC 9700 / CHAPTERS

Chapters

For full details, tables, algorithms, and exceptions, read the original RFC.

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