|
A medium dependent interface (MDI) describes the interface (both physical and electrical) in a computer network from a physical layer implementation to the physical medium used to carry the transmission. Ethernet over twisted pair also defines a medium dependent interface crossover (MDI-X) interface. Auto MDI-X ports on newer network interfaces detect if the connection would require a crossover, and automatically chooses the MDI or MDI-X configuration to properly match the other end of the link. ==Ethernet== The popular Ethernet family defines common medium dependent interfaces. For 10BASE5, connection to the coaxial cable was made with either a vampire tap or a pair of N connectors. For 10BASE2 the connection to the coaxial cable was typically made with a single BNC connector to which a T-piece was attached. For twisted pair cabling 8P8C modular connectors are used (often incorrectly called "RJ45" in this context). For fiber a variety of connectors are used depending on manufacturer and physical space availability. With 10BASE-T and 100BASE-TX separate twisted pairs are used for the two directions of communication. Since twisted pair cables are conventionally wired pin to pin there are two different pinouts used for the medium dependent interface. These are referred to as MDI and MDI-X (medium dependent interface crossover). When connecting an MDI port to an MDI-X port a straight through cable is used while to connect two MDI ports or two MDI-X ports a crossover cable must be used. Conventionally MDI is used on end devices while MDI-X is used on hubs and switches. Some network hubs or switches have an MDI port (often switchable) to connect to other hubs or switches without a crossover cable. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Medium-dependent interface」の詳細全文を読む スポンサード リンク
|