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0x15: New Talks accepted!
by Jamal Hadi Salim 28 Jun '21

28 Jun '21

4 more talks accepted by the illustrious PC! 1) Nabil Bitar and Jamal Hadi Salim introduce Policy Tables (Ptables), an Access Control List (ACL) infrastructure inspired by the trio: IPtables, IPSet and Conntracking. The IPtables trio is very widely deployed and well understood from a management perspective but has ongoing performance challenges[1]. Ptables maintains the IPtables management semantics while overcoming the IPtables performance challenges. Ptables is implemented using eBPF at TC and XDP levels; however, it is intended to use whatever kernel mechanisms available to meet desired goals. Alternative proposals take an _evolutionary_ approach by keeping IPtables ABI compatibility (either by adding kernel or libiptc transform layers); they have so far failed to see wide adoption. The authors instead take a _revolutionary_ approach by ignoring the ABI altogether and focusing on the semantic equivalence presented to the IPtables crafts-person. Ptables does not strive to be a full replacement for IPtables; instead, it takes a minimalist approach to cover the most common use cases while leaving room for innovating on new ideas. In this talk the authors will discuss the architecture and design choices taken as well as implementation challenges faced fitting eBPF. They will also discuss future plans. 2)Ping and Traceroute have served us well over the years, however they have been overcome by events in the networking world and do have shortcomings. Ron Bonica discusses revamping these tools. Ron describes the improvements over ping in the new PROBE diagnostic tool described in IETF RFC 8335. He also discusses ICMP extensions detailed in IETF RFC 5837 to enhance traceroute. Ron will further discuss the contributions they have made to the Linux kernel and user space tooling to enable both these extensions. The talk will describe the tooling details and contributions involved. 3) Qizhe Cai, Shubham Chaudhary, Midhul Vuppalapati, Jaehyun Hwang and Rachit Agarwal have spent a year analyzing Linux network stack performance issues in a data centre environment. While a lot of prior performance evaluations are centred around short-lived TCP flows, studies show that data centre flows mostly tend to be lived. This changes the reality of where the bottlenecks are. Example, the authors found that in fact the dominant bottleneck is kernel<->user copies as opposed to TCP processing which reveals its head when the focus is on short flows. The study also looks at, amongst other things, the effect of ever increasing data centre wire speeds(and the resulting bandwidth-delay products) on modern CPU cache sizes and calls out for new mechanisms for network-aware CPU scheduling. The authors will make recommendations and discuss challenges met. 4) Maxim Mikityanskiy describes how to accelerate synproxy with XDP. SYN cookies are a popular stateless DOS mitigation mechanism in which the sequence number of the first ACK is chosen as the result of a cryptographic hash function over easily computed parameters. Though effective, in Linux this requires traversing the network stack all the way to the socket layer. The extra compute cycles limits the rate of issuing SYN cookies. Maxim describes using eBPF at the XDP level to check SYN cookies without binding to a socket. The effort includes adding new eBPF helpers to aid this effort. [1] https://netdevconf.info/0x15/session.html?talk-linux-ACL-performance-analys… cheers, jamal

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0x15: New Talks accepted!
by Jamal Hadi Salim 27 Jun '21

27 Jun '21

4 more exciting talks accepted by the illustrious PC. 1) Ido Schimmel and Petr Machata will discuss the kernel 5.13 feature supporting resilient nexthop groups. Resilient NH groups are intended to minimize disruption in flow routing when changes are made to the group composition and weights of constituent nexthops. This talk will detail the inner workings of resilient nexthop groups, including hardware offload. The talk will also cover future work such as static resilient nexthop groups, Nexthop group consolidation, and integration into FRR. 2)Kostis Kaffes, Jack Tigar Humphries, David Mazières, and Christos Kozyrakis address the notion that OS schedulers often, if not always, have discrepancy in their algorithms that do not take care of what networked applications need because they lack system level insight into those needs. There is a lack of coherency in the kernel between the scheduling and the various layers, including the network stack, NICs, and applications. The result is suboptimal scheduling decisions which are often solely responsible for applications poor latency and throughput. Kostis et al propose "Maple" - a framework for user-defined scheduling. A user expresses an application-specific scheduling policy in a few lines of ebpf code and then deploys it across system layers without modifying their code. Kostis et al claim up 8× performance improvement compared with default policies. 3) Mark Claypool, Benjamin Peters, Pinhan Zhao, and Jae Won Chung evaluate TCP Hystart performance on satellite links. To avoid overshooting TCP slow start ramp up, the Linux kernel has a Hystart mode (on by default) that will exit slow start before packets are lost. Mark et al demonstrate that Hystart-Delay often causes spurious exit of slow-start on the satellite links they tested. This has big implications for efficient utilization of commercial satellite Internet links. Mark et al will be seeking suggestions from the community on how to overcome these challenges. For the moment, they have a suggested configuration which is being used as a short term solution. They will also briefly discuss future work to address the issue. 4) Eric Dumazet is not a man who uses many words. The title of his talk is simply "Big TCP". In this talk he discusses challenges faced when the network stack now has to deal with 200/400Gbit speeds. How to address this? Once one reduces or avoids use<->kernel copying the size of TSO/GRO packets matters. In this talk Eric will present how we can override current limits and reduce TCP/IP stacks overhead. cheers, jamal

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0x15: New Talks accepted!
by Jamal Hadi Salim 26 Jun '21

26 Jun '21

4 new exciting talks have been accepted by the PC 1) Alex Markuze takes another crack at dealing with socket overhead. Most solutions overcome the overhead by moving the processing to user space via zero copy. Alex will describe a new approach called MAIO with kernel/userspace shared memory pages from a dedicated allocator. Unlike DPDK, the kernel tcp stack is used by means of dedicated rx/tx kernel threads+kernel tcp sockets. 2) Jesse Brandeburg and Brett Creeley describe PowerMAN, a user space tool for Dynamic Interface Power Management. NIC hardware buffering is not keeping up with increasing speeds. Achieving maximum performance implies tuning the NICs which typically comes at the cost of power consumption. PowerMAN addresses these issues. Jesse and Brett are looking for feedback: Should this tool move in-kernel or stay in user-space? Much of the work may be more appropriate for the kernel scheduler to be involved. 3) Boris Pismenny, Yoray Zack, Ben Ben-Ishay and Or Gerlitz will discuss work on Autonomous NVMe-TCP offload. Traditional approaches to offloading NVMe-TCP require offloading a lot of L4 functionality: TCP, IP, routing, QoS, NAT, firewall, etc Not only is this undesirable given the complexity - but is also easily mitigated for bulk storage using batching as demonstrated in 0x14 talk[1]. Boris et al present how to offload CPU-intensive operations that cannot be optimized away using batching or clever software engineering: copy and CRC independent of L4 functionality. 4) Nabil Bitar and Jamal Hadi Salim describe their performance work on Linux ACL subsytems. Their work was motivated by lack of existing extensive comparison that fairly evaluate both _forwarding_ and _host_ workloads. The comparison is modeled using a widely deployed iptables use case. They look at: Iptables(with and without conntracking), IPtables with IPSet (with and without conntracking), XDP/ebpf, tc/ebpf, and tc/flower. They analyse both control path as well as data path performance under a variety of conditions. They are hoping their experience will help others in the community make decisions as to what approach to take under given circumstances. They are hoping as well to get community feedback and evolve the work further. cheers, jamal [1] https://netdevconf.info/0x14/session.html?talk-NVMe-over-TCP-is-not-NVMe-ov…

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0x15: New workshop and Tutorial accepted
by Jamal Hadi Salim 25 Jun '21

25 Jun '21

Two new sessions accepted. 1) Alexander Lobakin and Jesper Dangaard Brouer will chair the XDP workshop. Details: https://netdevconf.info/0x15/session.html?workshop-XDP-general 2) First tutorial on an extremely important but often over-looked topic in the Linux Network stack, Time Synchronization over ethernet. In this tutorial Maciej Machnikowski will go from introduction to details on the topic. Details: https://netdevconf.info/0x15/news.html?time-sync-over-ethernet-tutorial-acc… cheers, jamal

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0x15: Keynote speaker, Hari Balakrishnan
by Jamal Hadi Salim 24 Jun '21

24 Jun '21

We are honored to announce industry luminary and academic elite Hari Balakrishnan as the keynote speaker for Netdev conf 0x15. From an industry perspective: Hari is currently the co-founder and CTO at Cambridge Mobile Telematics which raised $500M funding[1] (yes, you heard that right) from The SoftBank Vision Fund. Over his illustrious career Hari has played the role of founder or advisor to many companies - typically created by his students at Massachusetts Institute of Technology (MIT). From an academic perspective: if you are involved in computer networks, networked systems, and/or mobile computing you are very likely to have come across Hari's contributions which are highly cited; he has an h-index of 125. To give you perspective of what 125 means: According to Hirsch[2], a person with 20 years of research experience with an h-index of 20 is good, 40 is great, and 60 is remarkable. You do the math;-> He is a recipient of many many awards, to highlight a few: Early days: - His PhD thesis on reliable data transport over wireless networks won the 1998 ACM doctoral dissertation award for best thesis in computer science. - Several best paper awards including the 2004 IEEE William R. Bennett Prize, and six "test of time" awards for papers with long-term impact. More recent: - the Infosys Prize for Engineering and Computer Science, the most prestigious award "... for his broad contributions to computer networking, his seminal work on mobile and wireless systems, and for commercial use of mobile telematics to improve driver behavior and make roads safer around the world" - The 2021 IEEE Koji Kobayashi Computers and Communications Award for "broad contributions to computer networking and mobile and wireless systems." Hari is currently the Fujitsu Professor of Computer Science and Artificial Intelligence in the Department of Electrical Engineering and Computer Science at MIT. More details can be found on Wikipedia: https://en.wikipedia.org/wiki/Hari_Balakrishnan So when Hari makes time to speak, pay attention. What does he want to talk to us about? He would like to describe the impact of new work he is involved in on _Site-to-Site Internet Traffic Control_. To quote: " Queues allow network operators to control traffic: where queues build, they can enforce scheduling and shaping policies. In the Internet today, however, there is a mismatch between where queues build and where control is most effectively enforced; queues build at bottleneck links that are often not under the control of the data sender. To resolve this mismatch, we propose a new kind of middlebox, called Bundler, which moves queues away from uncontrollable network locations to edge devices. This talk will describe how the use of signal processing methods in congestion control, combined with Linux kernel tricks, can enable an effective and scalable site-to-site traffic controller using Bundler. I will also describe some recent work in using verification methods to improve congestion control robustness. " Please come listen, hear him and engage him. cheers, jamal [1] https://www.businesswire.com/news/home/20181219005339/en/Cambridge-Mobile-T… [2] https://paperpile.com/g/what-is-a-good-h-index/

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0x15: New workshops accepted!
by Jamal Hadi Salim 23 Jun '21

23 Jun '21

The program committee has accepted 5 workshops. 1) Stefan Schmidt will chair the IoT Networking Workshop Details: https://netdevconf.info/0x15/session.html?workshop-iot-networking 2) Jamal Hadi Salim will chair the Traffic Control Workshop Details: https://netdevconf.info/0x15/session.html?workshop-traffic-control 3) Florian Westphal will chair the Netfilter Mini-Workshop Details: https://netdevconf.info/0x15/session.html?workshop-netfilter 4) Donald Sharp and Stephen Worley will chair the FRR Workshop Details: https://netdevconf.info/0x15/session.html?workshop-FRR 5) Roopa Prabhu and Jiri Pirko will chair the Switchdev Offload Workshop Details: https://netdevconf.info/0x15/session.html?workshop-switchdev-offload cheers, jamal

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0x15: Bronze Sponsor, Mojatatu!
by Jamal Hadi Salim 14 Jun '21

14 Jun '21

We welcome back Mojatatu with a bronze sponsorship for Netdev conf 0x15. Thank you for your generosity. Mojatatu believes in giving back to the Linux netdev community and has supported every single Netdev conf since inception. Mojatatu continues to pioneer in next generation SDN. cheers, jamal

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0x15: New Bronze sponsor! MobiledgeX
by Jamal Hadi Salim 09 Jun '21

09 Jun '21

We are pleased to announce Bronze sponsorship from MobiledgeX (https://mobiledgex.com/)! Mobiledgex is happy to sponsor open source communities like netdev as we benefit from open source and contribute back to eco systems to build out open telco edge clouds for the benefit of all cloud consumers. cheers, jamal

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0x15: Media sponsor! LWN
by Jamal Hadi Salim 08 Jun '21

08 Jun '21

We'd like to welcome back LWN.net as our media sponsor. Thank you for the support LWN! More about LWN: LWN.net(https://lwn.net/) aims to be the premier news and information source for the free software community. We provide comprehensive coverage of the development of the Linux kernel and other open-source software projects, information on security issues and concerns, as well as other topics relevant to those communities. The LWN.net Weekly Edition is our weekly summary of what has gone on, while the front page is updated frequently with news of interest from those worlds. cheers, jamal

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0x15: Bronze Sponsor! Linode
by Jamal Hadi Salim 07 Jun '21

07 Jun '21

We are pleased to welcome Linode as a bronze sponsor for Netdevconf 0x15. Thank you for your support Linode! A little bit more about Linode: Linode(https://www.linode.com/) believes that in order to accelerate innovation in the cloud, virtual computing must be more accessible, affordable and simple. Our infrastructure-as-a-service platform is deployed across 11 data centers around the globe and is supported by our Next Generation Network, advanced APIs, comprehensive services and vast library of educational resources. Linode products, services, and people enable developers and businesses to build, deploy and scale applications more easily and cost-effectively in the cloud. cheers, jamal

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