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Fiber Optics Illustrated Dictionary - Part 107

The Fiber Optics Illustrated Dictionary - Part 107 fills a gap in the literature by providing instructors, hobbyists, and top-level engineers with an accessible, current reference. From the author of the best-selling Telecommunications Illustrated Dictionary, this comprehensive reference includes fundamental physics, basic technical information for fiber splicing, installation, maintenance, and repair, and follow-up information for communications and other professionals using fiber optic components. Well-balanced, well-researched, and extensively cross-referenced, it also includes hundreds of photographs, charts, and diagrams that clarify the more complex ideas and put simpler ideas into their applications context | Fiber Optics Illustrated Dictionary Appendix B Asynchronous Transfer Mode ATM Information asynchronous transfer mode ATM. ATM is a highly significant protocol due to its flexibility and widespread use for Internet connectivity. It is a high-speed cell-based connection-oriented packet transmission protocol for handling data with varying burst and bit rates. ATM evolved from standardization efforts by the CCITT now the ITU-T for broadband ISDN BISDN in the mid-1980s. It was originally related to Synchronous Digital Hierarchy SDH standards. ATM allows integration of local area network LAN and wide area network WAN environments under a single protocol with reduced encapsulation. It does not require a specific physical transport and thus can be integrated with current physical networks. It provides virtual connection VC switching and multiplexing for broadband ISDN to enable the uniform transmission of voice data video and other multimedia communications. Two methods for carrying multiprotocol connectionless traffic over ATM are routed and bridged Protocol Data Units PDUs . Routed PDUs allow the multiplexing of multiple protocols over a single ATM virtual circuit through LLC Encapsulation. Bridged PDUs carry out implicit higher-layer protocol multiplexing through virtual circuits VCs . ATM employs fixed-length cells consisting of an information field and a header. The information field is transparent through the transmission. The U.S. and Japan proposed the use of 64-byte cells and Europe proposed 32-byte cells. As a consequence of the discrepancy 48-byte cells are favored by many as a compromise. Charts and simplified diagrams on the following pages show an ATM system through user input and reception of a variety of media including voice video and data. The data are inserted and extracted by the ATM adaptation layer AAL into a logical package called a pay load which makes up part of the ATM cell. The ATM layer in turn adds or removes a five-byte header to this payload