IP Fragmentation & Reassembly

• network links have MTU (max.transfer size) - largest possible link-level frame.

  • different link types, different MTUs

• large IP datagram divided (“fragmented”) within net

  • one datagram becomes several datagrams
  • “reassembled” only at final destination
  • IP header bits used to identify, order related fragments

fragmentation:

in: one large datagram

out: 3 smaller datagrams

reassembly

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