This January 2023 issue contains five technical papers.

The first technical paper, Fast In-kernel Traffic Sketching in eBPF, by Sebastiano Miano and colleagues, studies how to develop high-performance network measurements in eBPF. The extended Berkeley Packet Filter (eBPF) allows to dynamically load and run micro-programs in the Linux kernel without the need for recompiling it. The authors use sketches as case-study, given their ability to support a wide-range of tasks while providing low-memory footprint and accuracy guarantees. The authors apply their approach to a state-of-the-art sketch for user-space networking, show that best practices in user-space networking cannot be directly applied to eBPF, and improve its performance by 40% compared to a naive implementation. The lessons learned in this paper are not only applicable to network measurement algorithms but extend to a wide variety of eBPF-based programs.

The second technical paper, Comparing User Space and In-Kernel Packet Processing for Edge Data Centers, by Federico Parola and colleagues, is motivated by the increased availability of small data centers at the edge of the network. Network operators are moving their network functions in these computing facilities. However, commonly used technologies for data plane processing such as DPDK, based on kernel-bypass primitives, provide high performance but at the cost of rigid resource partitioning. This is unsuitable for edge data centers in which efficiency demands both general-purpose applications and data-plane telco workloads to be executed on the same (shared) physical machines. In this respect, eBPF/XDP looks a more appealing solution, thanks to its capability to process packets in the kernel, achieving a higher level of integration with non-data plane applications albeit with lower performance than DPDK. This research addresses the premise that in edge data centers, with limited resources, packet processing and protocol stack workloads are likely to be consolidated within the same servers. As a result, kernel-based XDP may be a more attractive option than DPDK-based data plane processing. This motivates the need for a deeper understanding of kernel-based XDP and its various forms to support different workload types.

The third technical paper, P4RROT: Generating P4 Code for the Application Layer, by Csaba Györgyi and colleagues, proposes a new code generation mechanism to streamline application-level offloads expressed in the P4 programming language. The authors present P4RROT, a new library that allow developers to write application layer logic in Python which is then converted in P4. The authors discuss the pain points and challenges for automatic code generation and show the applicability of P4RROT in two different contexts: a publish-subscribe sensor data processing system and a real-time data streaming engine, supporting MQTT-SN and MoldUDP traffic.

The fourth technical paper, The Slow Path Needs an Accelerator Too!, by Annus Zulfiqar and colleagues, shows that the slow path is set to become a new key bottleneck in Software-Defined Networks (SDNs). The authors present their vision of a new Domain Specific Accelerator (DSA) for the slow path at the end host that sits between the hardware-offloaded data plane and the logically-centralized control plane. They also discuss open problems and call on the networking community to creatively address this emerging issue.

The fifth technical paper, Who squats IPv4 Addresses?, by Loqman Salamatian and colleagues, analyzes the phenomenon of squatted IP space: IPv4 addresses that operators use although they have not been allocated to them. This is possible because larger IPv4 blocks exist that have been allocated to organizations which never announced them in the global routing system. The authors draw on a very large data set of traceroutes and develop a heuristic to identify how squat space is used, by whom, and what the implications for Internet routing and the operator communities are. This paper is a significant contribution of interest to everyone with an interest in the operation of Internet routing and larger networks.

I hope that you will enjoy reading this new issue and welcome comments and suggestions on CCR Online (https://ccronline.sigcomm.org) or by email at ccr-editor at sigcomm.org.