Patent ID: 7062569

Claim:
A control device for use in each of plural network units that are connected in cascade for conveyance of packets therebetween, the control device comprising: a down port for receiving and transmitting at different times respective control messages each containing a respective count value; an up port for transmitting and receiving at different times respective control messages each containing a respective count value; a first register for storing a unit identification count value; a second register for storing a total unit count value; and control logic organized: (a) in an up transmitting phase: (i) in the presence of a valid unit identification count value in said first register, to provide for a first control message from said up port an incremented unit identification count value; (ii) in the absence of a valid unit identification count value in said first register to provide for said first control message an out of range count value; (iii) in response to a count value in a second control message received at said down port, to store the same count value in said first register; and (iv) in the absence of any control message at said down port, to initialize said first register with an initial valid count value; and (b) in a down transmitting phase distinct from said up transmitting phase: (i) to transmit from said down port a third control message with a count value corresponding to a count value in said second register; (ii) in the presence of a fourth control message at said up port, to store in said second register a count value from said fourth control message; and (iii) in the absence of any control message at said up port to store in said second register said incremented unit identification count value.