At&t Bell Laboratories

Anne A Robrock

Wing N Toy

Mikiel L Larson

Trunk controllers (131) at each end of a trunk (118) of a packet switching system (FIGS. 1A and 1B) include an idle packet generator (1419) and an idle packet detector (1420). During idle periods, when packets are not available for transmission, the transmitter of each idle trunk controller generates and transmits a continuous sequence of flags (801/810) on the trunk. Periodically during the idle periods, the idle packet generator generates and provides to the transmitter (1403) for transmission an idle packet (800). An idle packet is structured like a normal packet. However, it is marked as an idle packet by the packet identification (PID) field (804) and contains pseudo-random bits in the data field (806). The receiver (1402) of the other trunk controller receives the idle code and packets including idle packets, discards the idle code, and sends all packets to the idle packet detector. The detector identifies idle packets by their PID field and discards them--blocks them from propagating further--while allowing other packets to pass therethrough.

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Milan, Italy

Anne A Robrock