ATM (Asynchronous Transfer Mode). Layer 2 protocol of the OSI model. Developed by CNET and a few manufacturers of computer components. The ATM technique is based on segmentation data cell size. The header of the cell contains information allowing each cell to find its way: it shows between the identity of another (VCI Virtual Channel Identifier) which the cell belongs. The VCI value is local to the switch, its value changes the output of each switch, indicating a new value for the next node. The ATM switch has a table giving the VPI / VCI based on the output VPI / VCI entry. An entry in this table is created each time a connection is established, the route is then established for the duration of the connection. Currently, two types of switching technologies are available:
- Packet switching (and frame relay), well suited for data transmission.
- Circuit switching, which takes into account the isochronous nature of telephone service