Meaning of SEGMENTATION in English
< networking > (Or "segmentation and reassembly", SAR) Breaking an arbitrary size packet into smaller pieces at the transmitter. This may be necessary because of restrictions in the communications channel or to reduce latency . The pieces are joined back together in the right order at the receiver ("reassembly"). Segmentation may be performed by a router when routing a packet to a network with a smaller maximum packet size.
The term "segmentation" is used in ATM , in TCP/IP , it is called "fragmentation" an is performed at the IP layer before the "fragments" are passed to the transport layer .
See for example ATM forum UNI 4.0 specification.
FOLDOC computer English dictionary. Английский словарь по компьютерам FOLDOC. 2012