ATM is the information transmission technology that combines the advantages of circuit switching (real-time communication) with bandwidth-management efficiency characteristic of packet switching. ATM is an asynchronous transfer technology for multiplex heterogeneous information (data, voice, video, etc.) on a common infrastructure. The ATM technique is based on segmenting data into single-size cells of 53 bytes (which differentiates it from a packet, which is of varying size). The header of the cell (5 bytes) contains the information allowing each cell to find its way: it indicates among other things the virtual channel identifier (VCI) to which the cell belongs. The VCI is local to the switch, it is re-written at the output of each switch, taking a new value for the next node. ATM was still a developing technology, and that is partly why it is not yet widespread. Some even consider this technology as already obsolete, since IP is now unavoidable and master of the Internet world, and in the sense that now other technologies, such as giga-Ethernet can supplant it at very low cost (No need to change the entire network infrastructure, since it is Ethernet).

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