In data communications networks, packet segmentation is the process of dividing a data packet into smaller units for transmission over the network. Packet segmentation happens at layer four of the OSI model; the transport layer.[1] Segmentation may be required when:
Protocols that perform packet segmentation at the source usually include a mechanism at the destination to reverse the process and reassemble the original packet from individual segments. This process may include automatic repeat-request (ARQ) mechanisms to detect missing segments and to request the source to re-transmit specific segments.
In a communication system based on a layered OSI model, packet segmentation may be responsible for splitting one MPDU into multiple physical layer service data units so that reliable transmission (and potential re-transmission via ARQ) of each one can be performed individually.
The ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 gigabit/s) local area network using existing home wiring (power lines, phone lines and coaxial cables), is an example of a protocol that employs packet segmentation to increase reliability over noisy media.