EFD: An Efficient Low-Overhead Scheduler

Size-based scheduling methods receive a lot of attention as they can greatly enhance the responsiveness perceived by the users. In effect, they give higher priority to small interactive flows which are the important ones for a good user experience. In this paper, we propose a new packet scheduling method, Early Flow Discard (EFD), which belongs to the family of Multi-Level Processor Sharing policies. Compared to earlier proposals, the key feature of EFD is the way flow bookkeeping is performed as flow entries are removed from the flow table as soon as there is no more corresponding packet in the queue. In this way, the active flow table remains of small size at all times. EFD is not limited to a scheduling policy but also incorporates a buffer management policy. We show through extensive simulations that EFD retains the most desirable property of more resource intensive size-based methods, namely low response time for short flows, while limiting lock-outs of large flows and effectively protecting low/medium rate multimedia transfers.