TAILIEUCHUNG - Kỹ thuật truyền số liệu 19

Tham khảo tài liệu 'kỹ thuật truyền số liệu 19', giáo dục - đào tạo, cao đẳng - đại học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | IAPTER 19 ATM Asynchronous Transfer Mode ATM is the cell relay protocol designed by the ATM Forum and adopted by the ITU-T. The combination of ATM and B-ISDN will allow high-speed interconnection of all the world s networks. In fact ATM can be thought of as the highway of the information superhighway. DESIGN GOALS Among the challenges faced by the designers of ATM six stand out. First and foremost is the need for a transmission system to optimize the use of high-data-rate transmission media in particular optical fiber. In addition to offering large bandwidths newer transmission media and equipment are dramatically less susceptible to noise degradation. A technology is needed to take advantage of both factors and thereby maximize data rates. Second is the need for a system that can interface with existing systems such as the various packet networks and to provide wide area interconnectivity between them without lowering their effectiveness or requiring their replacement. ATM is potentially as effective a LAN and short-haul mechanism as it is a WAN mechanism. Its proponents hope that it will eventually replace the existing systems. Until that happens however the protocol provides mechanisms for mapping the packets and frames of other systems onto ATM cells. Third is the need for a design that can be implemented inexpensively so that cost would not be a barrier to adoption. If ATM is to become the backbone of international communications as intended it must be available at low cost to every user who wants it. Fourth the new system must be able to work with and support the existing telecommunications hierarchies local loops local providers long-distance carriers and so on . Fifth the new system must be connection-oriented to ensure accurate and predictable delivery. 554 CHAPTER 19 ATM And last but not least one objective is to move as many of the functions to hardware as possible for speed and eliminate as many software functions as possible again for speed . .

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