| 单词 | FDDI (Fiber Distributed Data Interface) |
| 释义 | FDDI (Fiber Distributed Data Interface) The ANSI standard (X3T9-5) for a dual, counter-rotating, fiber optic, token-passing ring LAN.The specification pegs the signaling rate at 125 Mbps and the transmission rate (i.e., data rate) at 100 Mbps due to the 4B/5B line coding technique. FDDI is intended for backbone applications, interconnecting major computing resources such as high speed switches, routers, and servers. As the FDDI maximum frame size is 9000 symbols (1 symbol = 4 bytes), Ethernet and Token Ring frames can easily be encapsulated within FDDI frames for backbone transport. FDDI specifies devices separations of as much as 1.2 miles (2 kilometers) over multimode fiber (MMF) and 37.2 miles (62 kilometers) over single-mode fiber (SMF), with excellent error performance.The dual counter-rotating ring provides considerable redundancy, but requires that all directly connected devices be dual-attached, which adds to the cost and complexity. In consideration of the high cost and fragility of optical fiber, standards were developed to extend connectivity to workstations via unshielded twisted pairs.Those standards are known variously as CDDI (Copper Distributed Data Interface) and TPDDI (Twisted Pair Distributed Data Interface). FDDI is considered obsolete, having been overwhelmed by simpler, higher speed switched Ethernet technologies such as 1000Base-LX, 1000Base-SX, and 10GBase-LR, LW. See also 10GBase-LR, 1000Base-LX, 1000Base-SX, 4B/5B, ANSI, backbone, CDDI, Ethernet, fiber optics, frame, LAN, LW, MMF, signaling rate, SMF, symbol, token passing, Token Ring, and TPDDI. 74570c06.qxd 9/11/07 12:21 PM Page 181 |
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