Asynchronous Transfer Mode (ATM) constitutes a protocol set in ATM reference mode to establish a mechanism for transporting all communication traffic on a packet (cell) fixed 53 bitstream. The fixed size package ensures fast and easy to implement exchange and multiple technical functions. ATM is a connection-oriented technology, that is, two network systems are to establish communications between each other, should notify all intermediate exchanges about their service requirements and traffic parameters.
The ATM reference mode is divided into three layers: ATM adaptation layer AAL, ATM layer, and physical layer. AAL connects higher-level protocols and ATM layers, which is mainly responsible for forwarding ATM cells from the upper layer to the ATM layer, and vice versa. After receiving forwarding information from the upper layer, AAL divides the data into a cell; after receiving forwarding information from the ATM layer, the AAL must recapstate the load to form an upper layer to identify the format, the above process is called segmentation and recombination SAR. Different AAL are defined to support different traffic or service types to apply to the ATM network.
