segmentation

cleav·age   (klē'vĭj)    n.   The act of splitting or cleaving. The state of being split or cleft; a fissure or division. Mineralogy The splitting or tendency to split of a crystallized substance along definite crystalline planes, yielding smooth surfaces. Embryology The series of mitotic cell divisions that produces a blastula from a fertilized ovum. It is the basis of the multicellularity of complex organisms. Also called segmentation. Any single cell division in such a series. Chemistry The splitting of a complex molecule, such as a polysaccharide, into simpler molecules. Informal The hollow between a woman's breasts, especially as revealed by a low neckline.

Main Entry: seg·men·ta·tion
Pronunciation: "seg-(")men-'tA-sh&n
Function: noun
1 : the act or process of dividing intosegments; especially : the formation of many cells from a single cell (as in a developing egg)
2 : annular contraction of smooth muscle (as of the intestine) thatseems to cut the part affected into segments —compare PERISTALSIS

segmentation seg·men·ta·tion (sěg'mən-tā'shən, -měn-)
n.
See cleavage.

segmentation 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.
[Better reasons?]
(1999-06-14)