Transaction ID ticket

The ZY command format will accept a Transaction ID from the ZIY. If this is provided, it will accompany the command and will be returned by the ZY to the ZIY along with the data generated by that command, allowing the ZIY to match input to output. The ZY reserves the TID numbers 0 through 999 for its own purposes. Currently it uses 0 when no TID is given by the ZY's client and when the ZY generates a command response without input from the ZY's client, but future releases will return other TID numbers within the range for events that occur not as a result of direct client requests. When communicating with the ZY, the ZIY will currently generate transaction IDs with values ranging from 1000 to 4,294,967,295 and back to 1000 again when the TID overflows. This very generous range will allow the ZIY to issue thousands of commands and process their returns without any worry of a duplicate TID.