A maintenance communication control system in an ISDN service.

摘要

A maintenance link is established according to a LAPD between the first and the second terminal units on a path through which subscribers' packet information is transmitted. In the first and the second terminal units, the first and the second communication state control means for having control for ensuring the consistency of the communication state between the two terminal units are provided by sending/receiving the communication state control information using the maintenance link. <IMAGE>