The present invention relates to a kind of method and systems, after guaranteeing that restarting procedure PSTN agreements fail as defined in V5 standards,First data link carries PSTN protocol signal messages. In the method, the observation of process is restarted in the first pause (TC3) starting, if time-out has tripping, which starts, and meets V5 standards using control protocol signal message by sending initiation message. According to the present invention, have in the first link carrying PSTN agreements and reverts to working order and execute inspection, it is carried out in order with determining whether that the second data link is intended to carry control protocol signal message, and the inspection, it is carried out in order until the second data link is intended to carry control protocol signal message, with when the second data link is in order messages, starting PSTN agreements restarting procedure is to report control protocol.
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