Data centers increasingly deploy commodity servers with high-speed network interfaces to enable low-latency communication. However, achieving low latency at high data rates crucially depends on how the incoming traffic interacts with the system’s caches. When packets that need to be processed in the same way are consecutive, i.e., exhibit high temporal and spatial locality, caches deliver great benefits.
In this paper, we systematically study the impact of temporal and spatial traffic locality on the performance of commodity servers equipped with high-speed network interfaces. Our results show that (i) the performance of a variety of widely deployed applications degrade substantially with even the slightest lack of traffic locality, and (ii) a traffic trace from our organization reveals poor traffic locality as networking protocols, drivers, and the underlying switching/routing fabric spread packets out in time (reducing locality).
To address these issues, we built Reframer, a software solution that deliberately delays packets and reorders them to increase traffic locality. Despite introducing μs-scale delays of some packets, we show that Reframer increases the throughput of a network service chain by up to 84% and reduces the flow completion time of a web server by 11% while improving its throughput by 20%.
Links : paper ; usenix
After encountering novel challenges arising at 100G speeds, a follow-up longer version of our MiddleClick paper has been published in the IEEE/ACM Transaction on Networking journal in 2021 with hardware offloading, and an improved algorithm for combining sessions.
The code has been reverted into FastClick, allowing to have unique state management for multiple VNFs, automatically combined. On top of this session system, one can easily modify TCP or HTTP streams on the fly without full termination!
Check out the paper ! The code has been merged to FastClick.
In this journal version, we extended our conference paper with additional, peer-reviewed material:
- We implemented our system on QUIC using P4 and Picoquic. This demonstrates that our approach does not depend solely on TCP timestamps. The code in ‘bmv2’ and ‘p4-tofino’ has been made publicly available. All of our code is available at https://github.com/cheetahlb/.
- We added an experiment using the Tofino implementation and the QUIC implementation of Cheetah for an HTTP webserver.
- We added an experiment to verify whether today’s OSes support TCP timestamp, have them enabled by default, and correctly echo the TCP timestamp set by a server.
- We added an experiment to verify the granularity of the TCP timestamp units used by some of the largest Alexa top 100 websites.
- We added a proof sketch on the size of the cookies given a number of servers.
- We added an implementation in bmv2 of the “TCP timestamp”-based system. We have also rewritten and published the P4- tofino code of the system. The implementation of the stateful LB is non-trivial as it requires the insertions/lookups/deletions operations to be applied in constant time (and more restrictions apply). We describe our implementation of a stack-based data structure for the Tofino in Section 4.3.
- We added a micro-benchmark of the performance of the Cheetah LB, e.g., compared SYN insertions with cuckoo, normal packets,
- We broke down the benefits of SSE parsing of TCP options instructions.
- We evaluated the packet processing latency overheads of realizing Cheetah on a Tofino for both the TCP timestamp and QUIC implementation.
- We clarified the design challenges in the introduction.
Check out the paper in open access !
Our paper “High-speed Connection Tracking in Modern Servers” will be presented by Massimo Girondi at the IEEE HPSR 2021, the 22nd International Conference on High-Performance Switching and Routing.
We have analyzed the performances of six different Hash Tables implementations, studying how to scale them across multiple cores and how to efficiently remove expired entries, benchmarking them with up to 100 Gbps traffic.
This is joint work Marco Chiesa and Massimo Girondi, the first author.
Read the paper here.
Early February we presented a talk at FOSDEM, a huge Open-Source gathering with my colleague Alireza Farshin. The video is now released!
In the talk we present FastClick with a short demo, do a round of existing alternative modular framework (VPP and BESS mainly) and then discuss the future of software dataplanes, which we believe our recent work PacketMill starts to address.
We mainly show how FastClick is still really up-to-date with competition and goes beyond sota with PacketMill’s enhancements. We also re-did an experiment at 100G showing how FastClick now improves Click by more than 30x in a forwarding configuration. This is because we continued to maintain FastClick since nearly 6 years now and we do consider pull requests, and integrate recent research while good old Click itself is sadly stalling since a decade now. I will do a blog post about the state of FastClick in the next weeks.
I also bought the www.fastclick.dev domain to start a little showcase website. For now it redirects to GitHub. Feel free to help 🙂
Links : video ; slides ; page