tailieunhanh - Mạng và viễn thông P21

Campus and Metropolitan Area Networks (MANs) Metropolitan area networks (MANs) are network technologies similar in nature to local area networks (LANs), but with the capability to extend the reach of the LAN across whole cities or metropolitan areas, rather than being limited to, say, 100-200 metres of cabling. MANS have evolved because of the desire companies to extend LANs throughout company office buildings of spread across a campus or a number of different locations in a particular city. | Networks and Telecommunications Design and Operation Second Edition. Martin P. Clark Copyright 1991 1997 John Wiley Sons Ltd ISBNs 0-471-97346-7 Hardback 0-470-84158-3 Electronic 21 Campus and Metropolitan Area Networks MANs Metropolitan area networks MANs are network technologies similar in nature to local area networks LANs but with the capability to extend the reach of the LAN across whole cities or metropolitan areas rather than being limited to say 100-200 metres of cabling. MANs have evolved because of the desire of companies to extend LANs throughout company office buildings spread across a campus or a number of different locations in a particular city. They provide for high speed data transport at over 100 Mbit s and are ideal for the interconnection of LANs. There was some effort to extend MAN capabilities to include the carriage of telephone and video signals as an integrated network but this work has largely been overtaken by ATM asynchronous transfer mode so that the MAN technologies themselves are already obsolescent. We review here but only briefly the most important MAN techniques FDDI fibre distributed data interface and SMDS switched multimegabit digital service which is based on the DQDB distributed queue dual bus technique. FIBRE DISTRIBUTED DATA INTERFACE The fibre distributed data interface FDDI is a 100 Mbit s token ring network. It is defined in IEEE and ISO . FDDI can be used to interconnect LANs over an area spanning up to 100 km allowing high speed data transfer. Originally conceived as a high speed link for the needs of broadband terminal devices FDDI is now perceived as the optimum backbone transmission system for campus-wide wiring schemes especially where network management and fault recovery are required. In particular FDDI became popular in association with the very first optical fibre building cabling schemes because it provided one of the first means to connect LANs on different floors of a building or in different