An efficient packet scheduling algorithm in network processors

Several companies have introduced powerful network processors (NPs) that can be placed in routers to execute various tasks in the network. These tasks can range from IP level table lookup algorithm to application level multimedia transcoding applications. An NP consists of a number of on-chip processors to carry out packet level parallel processing operations. Ensuring good load balancing among the processors increases throughput. However, such multiprocessing also gives rise to increased out-of-order departure of processed packets. In this paper, we first propose a dynamic batch co-scheduling (DBCS) scheme to schedule packets in a heterogeneous network processor assuming that the workload is perfectly divisible. The processed loads from the processors are ordered perfectly. We analyze the throughput and derive expressions for the batch size, scheduling time and maximum number of schedulable processors. To effectively schedule variable length packets in an NP, we propose a packetized dynamic batch-coscheduling (P-DBCS) scheme by applying a combination of deficit round robin (DRR) and surplus round robin (SRR) schemes. We extend the algorithm to handle multiple flows based on a fair scheduling of flows depending on their reservations. Extensive sensitivity results are provided through analysis and simulation to show that the proposed algorithms satisfy both the load balancing and in-order requirements in packet processing.