C-1BASIC FDDI NETWORKSAPPENDIX CBASIC FDDI NETWORKSThis Appendix covers basic Fiber Distributed Data Interface (FDDI)network operation and concepts that are critical to FDDI networkdesign and installation. ANSI Standard X3T9.5 provides greaterdetail on FDDI access methods and should be referenced whenevermore complete information is needed. Specific areas that arepresented here include:• Basic FDDI Concepts• FDDI Devices• Design and Installation ConsiderationsBASIC FDDI CONCEPTSAn FDDI network is a high-speed network (100 Mbit/sec.) capable ofreliable data transmission using fiber optic cabling. The fiber opticmedia provides increased bandwidth, immunity from electrical noise,security, and permits the use of longer cable segments making FDDIa feasible alternative in LAN backbone applications, or as a back-endor front-end network between processors.FDDI Media Access ProtocolThe FDDI standard X3T9.5 describes the media access and tokenpassing protocol for FDDI networks. Each station attached to anFDDI ring is identified by a unique station address, differentiating itfrom all other stations. Transmission is controlled through the use ofa special frame called a token.The token holder is the only station that can transmit. The tokencirculates around the ring from station to station. Each stationreceives the token from the station preceding it on the ring, retains itwhile transmitting data (frames) and then passes (transmits) thetoken on to the next active station on the ring.
