ATM Cell

It is used with ATM, sending and receiving the minimum unit of the data which is done.The data which sending and receiving is done is divided every48bytes with ATM,53bytes whichheader information of 5 bytesare added become the ATM cell.The header of 5 bytes which are addedtothe ATM cell differsthe terminal-UNI which is used between network (User Network Interface) withNNI which is used between network (Node Network Interface) with with. In case of UNI, GFC (Generic Flow

Control: General-purposeflow control) 4bits, VPI which decides the address of the ATM cell (Virtual Path Indentifier:

Hypothetical identifier) 8bits, VCI (Virtual Channel Identifier: The hypothetical channel identifier) 16bits,PT whichthe

presenceof congestionand precedence of the ATM cell in the extent of congestion decides (Payload Type: Payload type)

3bits,CLP(Cell Loss Priority: Congestion loss priority) 1bit,HEC whichdoes the error detection of the header (Header Error Control: Control of header error) consists ofsix items of information of 8 bits. In case of NNI, it becomes information of 5 types which exclude GFC, but VPI reaches12 bits, the point where they are5bytes altogether does not change.