OSI MODEL

摘要

The OSI model is a conceptual framework that divides the task of internetworking into seven layers. Layer 1 (Physical): Describes how the bit stream-electrical impulse, light, or radio signal-moves through the network at the electrical/ mechanical (zeros/ones) level. Describes how hardware sends and receives data; defines cables, cards, and physical aspects. Protocols include R5-232, RJ-45, DSL, ISDN, the BaseTs, IEEE 1394 interface, USB, and B/uetooth physical layers.