METHOD AND DEVICE FOR PROTOCOL STATE SYNCHRONIZATION

摘要

PROBLEM TO BE SOLVED: To prevent an active side and a standby side protocol state from being unmatched and reduce a probability that a break of communication is caused in switching by forcibly changing the standby side protocol state according to the active side protocol state. SOLUTION: When an active side terminal station 5-A informs an active side central station 1A of fault occurrence, an active side upper-layer communication processing part 2-A sends a switching instruction to a standby side central station 1-S. The standby side upper-layer communication processing part 2-S having received it sends a forcible transition instruction to a standby side terminal station 5-S. Then a standby side protocol processing part 9-S of the terminal station 5-S having received it refers to a standby side state change TBL 8-S to rewrite a standby side state TBL 7-S of a terminal 12-1 in an active communication into an in-communication state, and the processing part 2-S becomes an active side and sends a stop instruction to the old active side processing part 2-A, which becomes a new standby side; and a line switching part 10-1 is switched to this station side and carries on the communication as a new active side.