Latency control in service chaining using P4-based data plane programmability

Abstract

Service chaining is becoming one of the most considered service deployment frameworks in the context of Network Function Virtualization (NFV) in edge and data center environments, conveniently supported by automatic connectivity configurations offered by Software Defined Networking (SDN). Current research on the topic is focusing on how to guarantee Quality of Service (QoS) in terms of guaranteed end-to-end latency for time critical services. Indeed, latency issues may depend on intra-server virtualization inefficiencies, leading to Virtual Network Function (VNF) delivery delays, or by congestion events occurring at intermediate network elements connecting VNFs. Latency control requires stateful information such as flow delay measurements at a per-packet level, typically not available at traditional SDN switches or inside the VNF. This paper proposes the adoption of SDN data plane programmability exploiting the P4 language and presents two P4 pipeline solutions, suitable for both intra-rack and inter-rack service chain deployments, to automatically check the path latency experienced by selected high priority flows, also resorting to the recent in-band telemetry applications. The programmable pipelines enforce proactive in-network functions, such as priority change or drop actions, in order to guarantee a bound SFC segment latency delivery, including both the network and the segment VNFs. The proposed solutions are implemented and evaluated in a network testbed employing programmable software switches showing their effectiveness in guaranteeing the configured end-to-end latency, and the limited effort in terms of additional processing at the P4 switch. The evaluation is carried out using the reference P4 software switch, i.e., BMv2. The aim is to validate the full P4 capabilities and the code feasibility in terms of scalability, load and resource impact and added intra-switch latency. The experimental results show the proposed approach scales with the number of forwarded flows and achieves per-segment latency control enforcement in both congested and non-congested scenarios with a very limited impact on the switch extra-latency, exploiting finer per-packet tuning of drop and priority change simply applicable through flow entry configuration. Applicability analysis on hardware switches guaranteeing line rate performance are provided.