ATM-ASYNCHRONOUS TRANSFER MODE (ATM)

5/24/97

Asynchronous Transfer Mode (ATM): ATM is a networking technology that theoretically allows networking speeds of 155, 622 or 2400MBit/Sec. Unlike alternatives such as Ethernet, ATM was devised by large communications companies to operate in the general world of communications rather than the specific world of local area networking. ATM is a high speed packet switching technology using small packets of 53 bytes (48 data, 5 header). ATM is intended to overcome the large number of empty packets sent in the earlier Synchronous Transfer Mode protocol. ATM packets can be sent directly over high speed T1/T3 telecommunication links. Because of its somewhat unusual genesis, ATM is subject to some unique problems and constraints -- particularly a need to minimize bursting of data which can cause lost data which must then be recovered by the use of higher level protocols. In practice, there seem to be difficulties in getting ATM to perform at specified speeds in real PC networks.

ATM has been described as "... a connection-oriented technology that provides the disadvantages of both circuit switching (e.g., complex call control and path selection procedures) and packet switching (e.g., real time congestion control)."

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