ATM is called asynchronous transfer mode. ATM is a network technology that transmits information in the form of fixed cells. The main objective behind the design of ATM was the integration of the services and performance requirements of both telephony and data network, which was briefly called Broadband Integrated Service Vision (B-ISDN). This cellular relay protocol was designed by the ATM forum and has been universally adopted by ITU-T. Usually the size of fixed cells is around 53 bytes with 5 bytes for the header and 48 bytes for the payload. Compared to the cell sizes used in previous technologies, the size of an ATM is small. The smaller size of ATM cells gives us a great advantage. ATM allows us to transmit video, audio and data over the same network, and the small size of ATM ensures that this data is delivered correctly. Establishing a connection in ATM is similar to circuit switching. First, a message is sent from the transmitter to the receiver to establish a connection. Subsequently all cells follow the same path to the destination. The connection that is established in this process is not a physical connection but virtual circuits. The ATM is designed in such a way that it can handle constant rate traffic and variable rate traffic. Therefore it can handle multiple types of traffic with end-to-end quality of service. Some of the key concepts of ATM were fixed packet sizes that allowed for faster switching, small packet sizes, statistical multiplexing, integrated services, good traffic management and engineering features, scalability in terms of network speed and size. DESIGN OBJECTIVES There were two main design objectives associated with the ATM ATM – an efficient transmission system and an interfaceable system. The following points will provide information on...... middle of paper...... transmission. This makes ATM suitable for transporting real-time data such as voice, video, etc. The fixed cell size (53 bytes) is also an added benefit to the ATM which ensures that the cell size does not vary across 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. Real-time data takes precedence over non-real-time data in ATM. The small, fixed cell size of ATM ensures that data is transmitted more efficiently and correctly when routed across the network. The ATM which has all these advantages has a disadvantage compared to emerging technologies and that is the cost. Some companies nowadays are moving towards Gigabit Ethernet in case they don't require many video conferencing and voice broadcast applications.