PURPOSE: To apply two-way reset service to the user by starting sequentially a unidirection reset of an SSCOP in both ways by a 2-way reset request from the user so as to realize the link set in both the directions.

CONSTITUTION: The method employs 1st and 2nd user terminal equipments 10, 20, an SSCOP link 30 and protocol data units PDU 40, 41. Then the users 1, 2 use the link 30 to make two-way communication. A 1st unidirectional reset is started in the direction of the other user 2 by the request from the user 1. Then the 2nd unidirectional reset is started in the direction of the user 1 after the start in the 1st unidirectional reset before the end of the 1st unidirectional reset. The user 1 informs it that 2-way reset is started to the user 2 after the end of 2nd unidirectional reset and when the user 2 requests the consecution of the two way reset, the 1st unidirectinal reset is finished and the user 2 informs it to the user 1 that the 2-way reset is finished.