A cost-effective technique to reduce HOL blocking in single-stage and multistage switch fabrics

Head-of-line (HOL) blocking is one of the main problems arising in input-buffered switches. The best-known solution to this problem consists of using virtual output queues (VOQs). However this strategy is not scalable at all. Its implementation cost increases quadratically with the number of ports in the switch. Taking into account current trends, the demand for larger number of ports in high-performance switches is likely to increase very rapidly in the near future. Therefore, a more scalable and cost-effective solution is required. We propose a very efficient and cost-effective technique, referred to as destination-based buffer management (DBBM), to reduce HOL blocking in single-stage and multistage switch. Results show that the use of the DBBM technique with a reduced number of queues at each IA is able to obtain roughly the same throughput as the VOQ mechanism. In particular, the number of queues can be reduced by a factor of up to 8 with the DBBM technique.