Editing IPv4 (section)

===Reassembly===
A receiver knows that a packet is a fragment, if at least one of the following conditions is true:
*The flag ''more fragments'' is set, which is true for all fragments except the last.
*The field ''fragment offset'' is nonzero, which is true for all fragments except the first.

The receiver identifies matching fragments using the source and destination addresses, the protocol ID, and the identification field. The receiver reassembles the data from fragments with the same ID using both the fragment offset and the more fragments flag. When the receiver receives the last fragment, which has the ''more fragments'' flag set to 0, it can calculate the size of the original data payload, by multiplying the last fragment's offset by eight and adding the last fragment's data size. In the given example, this calculation was <math>495 \times 8+540=4{,}500</math> bytes. When the receiver has all fragments, they can be reassembled in the correct sequence according to the offsets to form the original datagram.