US 6,982,993 B1
Virtual loop carrier system with network clock recovery
Denis Claveloux, Hudson, N.H. (US); and Sriram Narayan, Westford, Mass. (US)
Assigned to Cisco Technology, Inc., San Jose, Calif. (US)
Filed on Nov. 28, 2000, as Appl. No. 9/724,303.
Application 09/724303 is a continuation of application No. 09/441587, filed on Nov. 17, 1999, granted, now 6,731,627.
Claims priority of provisional application 60/130170, filed on Apr. 20, 1999.
Claims priority of provisional application 60/108924, filed on Nov. 17, 1998.
Int. Cl. H04J 3/06 (2006.01)
U.S. Cl. 370—503 12 Claims
OG exemplary drawing
 
1. A method of providing clock timing in a receiver, the method comprising:
providing a local clock signal having a reference frequency by dividing a local oscillator signal by a clock divisor having an initial nominal value;
receiving a stream of data cells in a receiver buffer;
servicing the receiver buffer to remove the data cells at a servicing rate based on the local clock signal;
monitoring fullness of the receiver buffer at a monitoring interval;
upon buffer fullness exceeding a high buffer threshold, adjusting the clock reference frequency upwards by setting the clock divisor to a value less than the nominal value and by stretching the local clock signal by half a cycle of the local oscillator signal;
upon buffer fullness dropping below a low buffer threshold, adjusting the clock reference frequency downwards by setting the clock divisor to the nominal value and by stretching the local clock signal by half a cycle of the local oscillator signal.