Importance

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Abstract

A method and apparatus for protection against loss of data in a fractional T1/E1 communications environment utilizes a message signaling arrangement between data service units and/or channel service units (DSU/CSU) to detect interruption in data transference occurring within a common carrier network due, for example, to an out-of-service condition. A 'heartbeat' signal in a proprietary message format is generated and sent on a periodic basis to one or more destination DSUs/CSUs through the common carrier network over a separate T1/E1 maintenance channel. A selectable duration watchdog timer at each DSU/CSU is reset every time a heartbeat signal message is received from a remote unit. If the heartbeat signal is not received within the specified amount of time, the watchdog timer expires triggering the DSU/CSU to enter a dial back-up mode wherein an alternate communications link is established. The 'heartbeat' method of the present invention thus results in faster detection of a loss of network communications condition in T1/E1 fractional environment than other more conventional methods such as, for example, a UNIX 'ping' command.

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First Claim