METHOD FOR RECOVERING BORDER OF PACKET

PROBLEM TO BE SOLVED: To realize a simple point-to-point data link protocol(SDL) based on the use of a length indicator field and an error check field not on the use of a flag to recover a packet border in a receiver. SOLUTION: An SDL transmitter 105 sends an SDL packet consisting of a header and a PDU (payload) of a variable length. The header consists of a length indicator (L1) field, a type field and a cyclic redundancy check CRC field. A receiver 150 blocks a packet as a function of the LI field to conduct self-synchronization as functions of the LI field and the header CRC field, that is, recovers the packet. In the recovering the packet especially, the receiver 150 applies CRC check to each reception SDL packet header and declares synchronization after the check by N times (e.g. N=4) is correct.