Enabling Rank-Based P4 Programmable Schedulers: Requirements, Implementation, and Evaluation on BMv2 Switches

Software-defined networking (SDN) has revolutionized network infrastructure, offering programmability to meet evolving network demands. However, the fixed-function nature of the packet scheduler in current network equipment impedes the exploration of scheduling policies within a programmable network environment. This paper proposes a novel methodology to implement rank-based programmable schedulers in programmable BMv2 switches expressed with the network-specific programming language (P4). A proposed custom networking environment facilitates the study and evaluation of various scheduling policies. This environment is used to implement 20 different scheduling and shaping policies to identify the required language constructs and components needed to express these policies with the P4 language efficiently. Our experiments reveal that specific scheduling policies do not seamlessly align with a previously proposed architecture for rank-based scheduling policies. Thus, we propose rank-based versions for five previously reported scheduling policies, making them efficiently implementable in any rank-based schedulers and programmable network equipment. The reported results confirm that the rank-based versions of these scheduling policies accurately replicate the behavior and performance of the original policies, with a maximum error of 0.5% in the resulting flow completion times (FCTs).