Abstract: An online system monitoring technique quickly and efficiently identifies failures or other system errors arising during operation of an intermediate network node, such as a network switch. The technique comprises Keep Alive Buffer packets/cells (“KABs”) that exercise data and control paths extending from every ingress port to every egress port in the switch. By exercising the data and control paths, the KABs enable testing of, and ensuring against, component failures, missing modules or other types of failure that can be detected as soon as possible, to thereby prevent data flow backup or other performance degradation in the switch.

Abstract: A technique synchronizes a crossbar switch fabric of a network switch having a plurality of modules configured to transmit and receive data at high speeds. The crossbar switch fabric resides on a switch module and operates on fixed-size cells received at its input ports from line card modules over high-speed serial communication paths of the switch. To eliminate resynchronization between the modules after each serial communications path traversal, each module is allowed to operate within its own clock domain, thereby forcing the entire resynchronization task upon a receive data path of the switch module. Although this results in resynchronization of a “large magnitude”, the task only needs to be performed once and entirely on the switch module.

Abstract: A clipping circuit and method for selecting a rectangular region of interest from an image comprised of scan lines of pixels. The circuit stores the lengths of the portions of scan lines inside and outside the region of interest. A data decompression unit presents image data to the clipping circuit in scan line order. When pixels from the portion of a scan line within the region of interest are processed, the circuit passes the pixels through the system. When pixels outside the region are processed, they are blocked from further processing by the circuit.