Asynchronous Transfer Mode for Transmitting Information

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ATM is called Asynchronous Transfer Mode. ATM is a networking technology which transmits information in the form fixed cells. The main vision behind designing ATM was integration of services and performance requirements of both telephony and data networking which was shortly called Broadband Integrated Service Vision (B-ISDN). This cell relay protocol was designed by ATM forum and was universally adopted by ITU-T. Usually the size of the fixed cells is about 53 bytes with 5 bytes for header and 48 bytes payload. When compared to the cell sizes used in the previous technologies, the size of an ATM is small. The smaller size of the ATM cells gives us a major advantage. ATM enables us to transmit video, audio and data over the same network and the small size of the ATM ensures that these data get delivered properly. Establishing a connection in ATM is similar to circuit switching. A message is first sent from the transmitter to the receiver to set up a connection. Subsequently all cells follow the same path to the destination. The connection that is set up in this process is not a physical connection but virtual circuits. ATM is designed in such a way that it can handle constant rate traffic and variable rate traffic. Hence it can handle multiple types of traffic with an end-to-end quality of service. Some of the key concepts in ATM were fixed packet sizes that allowed faster switching, Small packet size, Statistical multiplexing, Integrated services, Good Management and traffic engineering features, Scalability in speed and network sizes. DESIGN GOALS There were two main design goals associated with the ATM – an efficient transmission system and an interfacable system. The following points will brief abou... ... middle of paper ... ...transmission. This makes ATM suitable for carrying real time data like voice, video etc. The fixed cell size (53 bytes) also is an added advantage for the ATM which ensures that the cell size does not vary in the source and destination. ATM also offers pre-established secondary routes in case of traffic, congestion or network failure. Order of precedence is also an important feature of ATM. A real time data takes precedence over non-real time data in ATM. The small and fixed cell sizes of ATM ensures that the data is transmitted more efficiently and properly while being forwarded through the Network. ATM which has all these advantages has one drawback when compared to the emerging technologies and that is the cost. Some companies these days are moving towards Gigabit Ethernet in case they do not require much of videoconferencing and voice transmission applications.

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