gtpn1m09 | Non-SNA Data Communications Reference |
To start the exchange of information on a line, the center will send an Enquiry link control block down the line.
To stop the exchange of information on a line, the center will send a Stop Sending and, if there are outstanding unacknowledged blocks, an Enquiry link control block down that line. To stop the exchange of information on a link, the above procedure is repeated for each line of the link. Type A messages due for output on the link and multi-blocked messages not yet assigned an MBI will be discarded. Type B messages which need to be secured by the link Control Software will be retained for transmission later.