Uday Mudoi, Product Marketing Manager, Vitesse Semiconductor Corp.
Brian Branscomb, System Architect, Vitesse Semiconductor Corp.

Oversubscription of system bandwidth has become common in Ethernet networks due to the pressure to keep the price per port low. In this paper, we examine the Ethernet access processor (widely referred to as MAC) architecture required to support oversubscription of the switch/NPU bandwidth. We focus our attention on architectural requirements such as priority queuing, shared buffering, and hierarchical scheduling.

We show that these features need to be implemented at different complexity levels based on the service requirements. Finally, we explore implementation options with special emphasis on the buffer requirement of an oversubscribed MAC and the associated tradeoffs in terms of features, complexity, and cost-effectiveness.