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).

Software-defined Networking (SDN) introduced the decoupling of control and data forwarding planes. Despite advances in the programmability of SDNs, there remains a strong need for a fully programmable packet scheduler in the data plane. In this context, the ability to adapt to various traffic patterns and the expressiveness of schedulers are of paramount importance. This paper introduces the Dynamic Ranking Push-In-First-Out (DR-PIFO), as an algorithmic model that can be used to develop programmable packet schedulers based on PIFO queues. The DR-PIFO is a highly expressive model, capable of expressing a wide range of work-conserving, non-work-conserving, and hierarchical scheduling algorithms. Additionally, its dynamic ranking capabilities allow for real-time updates to the packet’s priority within the scheduler. The proposed solution also performs error detection in the departure order of packets, which is essential to avoid starvation in strict priority scheduling. These features are crucial when implementing popular scheduling algorithms such as the pFabric. The DR-PIFO is evaluated through its algorithmic properties and by implementing two distinct case studies. Its performance is further evaluated by incorporating it as an external module, written in a high-level language, and integrating it with software switches implemented using the P4 language. The results illustrate the superior expressiveness of DR-PIFO over state-of-the-art models such as PIFO and PIEO and confirm that it is an algorithm-agnostic model. Thus, DR-PIFO represents a promising solution for implementing more fully programmable packet schedulers in SDNs, with the potential to improve performance and adaptability.