This blog highlights the contributions made by a group of faculty, researchers, and doctoral students working on Networked Systems aspects. For open positions, please consult our Projects.
Today’s network functions require keeping state at the granularity of each individual flow. Storing such state on network devices is highly challenging due to the complexity of the involved data structures. As such, the state is often stored on inefficient CPU-based servers as opposed to high-speed ASIC network switches. In our newly accepted CoNEXT paper, we demonstrate the possibility to perform tens of millions of low-latency flow state insertions on ASIC switches, showing our implementation achieves 75x memory requirements compared to existing probabilistic data structures in a common datacenter scenario. A PDF of the paper will soon be available. This was joint work between Mariano Scazzariello, Tommaso Caiazzi (from Roma Tre University), and Marco Chiesa.
At ACM IPSN ’23 Daniel presented our work on DeepGANTT, a scheduler which demonstrates our ability to apply transformers to graph neural networks for scaling up an IoT scheduling problem 6X-11X beyond what a constraint optimization solver can solve in a reasonable time. Full abstract is below.
This is joint work with
Daniel F. Perez-Ramirez, Carlos Pérez-Penichet, Nicolas Tsiftes (RISE), Thiemo Voigt (Uppsala University and RISE), Dejan Kostić, and Magnus Boman (KTH).
Novel backscatter communication techniques enable battery-free sensor tags to interoperate with unmodified standard IoT devices, extending a sensor network’s capabilities in a scalable manner. Without requiring additional dedicated infrastructure, the battery-free tags harvest energy from the environment, while the IoT devices provide them with the unmodulated carrier they need to communicate. A schedule coordinates the provision of carriers for the communications of battery-free devices with IoT nodes. Optimal carrier scheduling is an NP-hard problem that limits the scalability of network deployments. Thus, existing solutions waste energy and other valuable resources by scheduling the carriers suboptimally. We present DeepGANTT, a deep learning scheduler that leverages graph neural networks to efficiently provide near-optimal carrier scheduling. We train our scheduler with optimal schedules of relatively small networks obtained from a constraint optimization solver, achieving a performance within 3% of the optimum. Without the need to retrain, our scheduler generalizes to networks 6 × larger in the number of nodes and 10 × larger in the number of tags than those used for training. DeepGANTT breaks the scalability limitations of the optimal scheduler and reduces carrier utilization by up to compared to the state-of-the-art heuristic. As a consequence, our scheduler efficiently reduces energy and spectrum utilization in backscatter networks.
Can networking applications achieve suitable performance with IOMMU at high rates? Our recent PeerJ CS article answers this question by characterizing the performance implications of IOMMU and its cache (IOTLB) on recent Intel Xeon Scalable & AMD EPYC processors at 200 Gbps. Our study shows that enabling IOMMU at high rates could result in an up-to-20-percent throughput drop due to excessive IOTLB misses. Moreover, we present potential mitigation techniques to recover the introduced throughput drop caused by the “IOTLB wall” by using hugepage-backed buffers in the Linux kernel. This is joint work with Alireza Farshin (KTH), Luigi Rizzo (Google), Khaled Elmeleegy (Google), and Dejan Kostic (KTH). Follow the links for PDF and code.”
On April 1, 2023 Professor Maguire became Professor emeritus connected to KTH Royal Institute of Technology, and on April 21 there was a ceremony in Stockholm to mark this event. Congratulations to Professor Maguire on a fantastic career that is nowhere near to being over!
Similarly to multi-core CPUs, also network devices increasingly rely on parallel packet processing engines to achieve insanely high throughput (up to 16 pipes to process 50 terabits per second on a single chip). In our recent paper accepted at ACM SIGMETRICS, we unveil, quantify, and mitigate the impact of deploying existing network monitoring mechanisms on multi-pipe network devices. Our design, called PipeCache, allows to reduce memory requirements (a constrained resource on ASIC devices) up to 16x! A PDF of the paper is available here. Code is available here.