Report and Abstract for Fiber Distributed Data Interface

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Fiber Distributed Data Interface
FDDI (Fiber Distributed Data Interface) is a set of ANSI and ISO standards for data transmission in computer networks or wide area network (LAN) via fiber optic cable. Architecture is based on the token ring and allows full duplex communication type. As can supply thousands of users, an FDDI LAN is often used as backbone for a wide area network (WAN).

There is also an implementation of FDDI in copper wire cables known as CDDI. Ethernet technology to 100 Mbps (100BASE-FX and 100BASE-TX) is based on FDDI.
OPERATION
An FDDI network uses two token ring architectures, one as support in case the primary fails. In each ring, the data traffic occurs in the opposite direction to the other. Using one of these rings the speed is 100 Mbps and range of 200 km, with both speed up to 200 Mbps but the low range to 100 km. The method of operation is very similar FDDI token ring to, however, the larger size of its rings leads to its upper and latency is a raster may be circulating in a ring at the same time.
FDDI was designed in order to achieve a real-time system with a high degree of reliability. It was considered as a design goal of virtually error-free transmission. That is why, among other things, that it was decided by the optical fiber as a medium for FDDI. It also specified that the total error rate of complete ring FDDI should not exceed an error every 1e9 bits (ie an error on gigabit) with a packet loss rate of data that exceeds either 1e9. In the case that a failure in a station or a wire breakage is avoided the problem area automatically without user intervention, by what is known as “back curve” (wrapback). This occurs when a fault is detected FDDI ring and drives traffic to the secondary ring so you can reconfigure the network. All stations are operating properly remain online and unchanged. As soon as the problem is corrected, restoring service in that area.
There are various devices for the management and use of an FDDI network:
• Simple docking station (SAS) (Single Attachment Station) are usually servers or routers that connect to both rings. A SAS implements a single type MIC S. Normally connected through a single segment to a hub transmission that implements a type MIC M. It contains an entity SMT, MAC sublayer entity, and a port with a MIC of type S.
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• docking stations or Dual-Doubles (DAS) (Dual Attachment Station) are designed for connecting separate segments of transmission means full-duplex, two rings. A station has dual SMT entity, one or more entities of the MAC sublayer, and exactly two ports. Each port has its own associated MIC. When each MIC is properly connected, forming two rings logical and physical.
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• Simple Connection Concentrator (SAC) (Single Attachment Concentrator) is not very reliable because it makes a simple connection. Can be used to create a hierarchical tree structure.
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• Dual Connection Concentrator (DAC) (Dual Attachment Concentrator) A hub with additional ports, in addition to the need for connection to the network. Additional ports can be used for connecting to other network stations. Using a dual hub or double connections, you get a station that has three or more ports, each associated with its own MIC.
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• Connection concentrator-null (NAC) (Null Attachment Concentrator). It is also possible to have a network formed only by a tree structure without double ring. In such a configuration, the concentrator is a concentrator highest void connections, NAC. A NAC has no connectors type A or B to connect to the double ring or S-type connectors to join a top-level hub. MIC’s has only type M, for connecting stations and concentrators lower level data.
FDDI specifies the physical layer and the data link layer of the OSI model, but not a single specification, but a set of four specifications isolated, each with a specific function. Together, these specifications have the ability to provide high-speed connectivity between upper layers such as TCP / IP and IPX and a medium such as fiber optic cabling. The four FDDI specifications are:
• Specifying MAC (Media Access Control) defines how the medium is accessed, including frame format, token handling, addressing, algorithms for calculating the value of CRC (cyclic redundancy check), and error recovery mechanisms .
• The specification PHY (Physical Layer Protocol) defines the procedures for data encoding and decoding, timing requirements (clocking), and framing, among other functions.
• The specification PMD (Physical-Medium Dependent) defines the characteristics of the transmission medium, including fiber optic links, power levels, bit error rates, optical components and connectors.
• The specification SMT (Station Management) defines FDDI station configuration, ring configuration, ring control features, including insertion and removal, initialization, fault isolation, planning and statistics collection.

History
FDDI began to be developed by the ANSI standards committee X3T9.5 in 1983. Each of its enhanced specification was designed and culminating with SMT in 1994. The reason for its existence was to be an alternative LAN ethernet and token ring ofreciese also increased reliability. Today, because of its superior speed, cost and ubiquity, it is preferred to use Fast Ethernet and Gigabit Ethernet instead of FDDI.

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