The Frame Relay Customer Premises Equipment (CPE) polls the switch at set intervals to determine the status of both the network and DLCI connections. A Link Integrity Verification (LIV) packet exchange takes place about every 10 seconds, verifying that the connection is still good. The LIV also provides information to the network that the CPE is active, and this status is exported at the other end. Approximately every minute, a Full Status (FS) exchange occurs, passing information regarding which DLCIs are configured and active. Until the first FS exchange occurs, the CPE does not know which DLCIs are active, and as such, no data transfer can take place.
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