ut the destination or fate of other cells traversing the core. Therefore, the overall switching decision function is conveniently distributed over the entire fabric core. The most common algorithms used in the arbitration context are dual round robin matching (DRRM), iterative round robin with matching (IRRM), iterative round robin with SLIP (iSLIP), FIRM, Parallel Iterative Matching (PIM), and round robin greedy scheduling (RRGS). The arbitra- tion context usually involves a handshake protocol starting with a request by the input queue for access to the shared resource (a fabric path in this case) and a grant issued by the arbiter followed by an accept acknowledgement from the input queue. Several sources discuss various arbitration algorithms in depth. 11-13 We will not discuss these algorithms. Although the arbiter must be able to scan all the inputs periodically and make a decision fast without causing a bottleneck, the fabric does not need to run faster than the input lines in such a configuration. We talk about output-buffered (or output-queued) switches whenever the packets are queued at the corresponding output stages after the packets have been actually switched over the fabric core. The HOL blocking phenomenon is eliminated in this case because any potential output congestion has already been transferred from the fabric core to the output buffers. In general, output buffering requires more storage space per output line than input buffering. The speed with which the write operation of switched packets can be accomplished on the output buffers is the critical factor. For these two rea- sons, it must be implemented in a faster circuit design. On both situations, however, this means that output buffering is a more expensive proposition. That is the price one pays for avoiding the HOL problem. An interesting and highly desirable side effect of output buffering is that per definition, it provides the systems designer with the possibility of a very fine granularity of traffic management. Decisions can be appli