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.

Abstract: Disclosed is a network device having a shared memory, a controller for storing Ethernet frames in frame buffers using data chaining to divide up at least the larger frames over a plurality of same sized buffers in the shared memory, wherein there is a tradeoff between using 1) larger buffers capable of receiving more of or all of the larger frames (more wasted buffer space) or 2) smaller buffers requiring more data chaining (wastes processing time to reassemble the frames) and an Ethernet driver having a buffer size adaptation routine which uses an algorithm to dynamically size the buffers.