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0x17: Talk, Zero Copy Receive using io_uring
by Jamal Hadi Salim 06 Oct '23

06 Oct '23

The war on memory bottlenecks[1][2] continues with this talk from David Wei and Pavel Begunkov. Socket recv() data is first copied/DMAed into the kernel memory and then again into user space memory - adding pressure to overall memory bandwidth and of course comes with a CPU cost. While there are other approaches to avoid the second copy on recv() such as DPDK, RDMA etc, David and Pavel argue that all of them have downsides - ranging from being proprietary, custom patched drivers, and difficult to debug and worse requiring a rewrite of the applications... Our esteemed speakers instead opt for continuing to use the network stack as is and io_uring as the user facing API. So what do we need to get this working? As in [2] that the NIC supports header splitting and RSS flow steering. On incoming data the headers traverse the TCP stack while data is DMA'ed not to the kernel memory but into user space... David and Pavel will discuss the overall approach they took and describe in some detail the kernel infra as well as what uapi would look like. They will further review kernel-existing zero copy approaches and how they plan to coexist with them. Last but not least they will dig into limitations and challenges of zero copy receive and how they overcome them to facilitate a real deployment. [1] https://netdevconf.info/0x17/sessions/talk/congestion-control-architecture-… [2] https://netdevconf.info/0x17/sessions/talk/device-memory-tcp.html cheers, jamal Reminder: 2 more days to go for early bird registration

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0x17: Talk, Device Memory TCP
by Jamal Hadi Salim 05 Oct '23

05 Oct '23

My apologies for putting some marketing at the top of this email: Reminder, Early bird ticketing is open for 2 more days; the sooner you register the better it is for our planning... And now to tell you about one of my favorite talks this time.. ML/AI continues to be an inspiration for new Linux kernel infrastructure and a theme at netdev conf 0x17! There are a couple of patterns in ML traffic that inspire this work from Mina Almasry, Willem de Bruijn, Eric Dumazet and Kaiyuan Zhang: 1) There is _a lot of freaking data_ being transferred across the network - and it continues to increase dramatically (ex: to accommodate such large data transfers NICs with 800 Gps ports are starting to appear) and 2) The vast majority of this data is typically from a device(eg storage) to another device (eg GPU). For context, assume a scenario where data transfers from SSDs on machineA cross the network to GPUs on machineB; and on machine B: In the rx direction incoming data into the NIC goes to host memory, then from host memory to the GPU. In the tx direction outgoing data goes from GPU to host then out to the NIC. This data movement approach, with multiple round trips across the memory and PCIe busses, is no longer tenable at such large amounts of data quantity. Current host hardware is just not equipped to deal with this. While such bulk transfers amount to low packets/sec rates, you are simply not going to be able to achieve wire speed because of the PCIe and memory bandwith abuse from the multiple round trips (see talk [1] which delves into host limitations). Almasry et al introduce Device Memory TCP to solve these challenges. They implement socket API to enable a user to send directly from device memory (GPU in machineB above example or SSD in machineA) across the network - as well as be able to place incoming data directly in the device memory (GPU in machineB example). How does this magic happen? Well, we need some support from the NIC to split the header on rx such that the TCP headers go to the host and the rest of the data goes directly to the device. The reverse is true for tx direction. Packet headers get to go to stack and get processed in the standard (TCP) code path. Memory bandwidth use is cut dramatically and because NIC to device transfers now happen at the lowest level of the PCIe tree hierarchy PCIe bandwidth use is also cut down dramatically. With devmem TCP, Almasry et al with a setup of 4 machines of GPU+100Gbps NICs - and data sent and received directly from/to device memory - were able to reach ~96.6% line rate speeds. In the talk they will go over details of the kernel/uapi changes to achieve devmem TCP. cheers, jamal [1] https://netdevconf.info/0x17/sessions/talk/congestion-control-architecture-…

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0x17: Talk, Lightweight Implementation of Per-packet Service Protection
by Jamal Hadi Salim 05 Oct '23

05 Oct '23

There are applications which MUST have reliable communication otherwise things fall apart! Think industrial automation, robotics, aerospace, automotive... Failure in timeliness of message delivery could be catastrophic. Typically when such a network is built, the operator makes sure that any congestion-related issues and packet losses are avoided. However, Murphy's law applies: the wiring may break, a radio link can be temporarily shielded by an obstacle, or worse the network nodes can be damaged... To deal with such losses, industry standardization has been introduced to provide per-packet service protection - these include Frame Replication and Elimination for Reliability(FRER) for Layer 2 Ethernet networks and the Packet Replication, Elimination, and OrderingFunctions(PREOF) forLayer3 IP/MPLS networks. Ferenc Fejes et al have implemented FRER in two different approaches: 1) in eBPF/XDP as a lightweight software implementation; and (2) in userspace using PF_PACKET. Ferenc et al will go over the architecture details of the two approaches and then evaluate XDP FRER via an experimental analysis and further compare the two FRER implementations. cheers, jamal Reminder: Three days to go before early-bird registration ends!

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0x17: Talk, Synce4l: open-source implementation of Synchronous Ethernet
by Jamal Hadi Salim 04 Oct '23

04 Oct '23

Almost _a quarter_ of the world-wide consumer Internet traffic is pushed through mobile networks! Wireless mobile network traffic requires tight time synchronization with wired components of the 5G/6G network. PTP with its sub-microsecond synchronization just doesnt cut it anymore and Michał Michalik and Arkadiusz Kubalewski say we need sub-nanosecond synchronization! The only way we can achieve this is to use Synchronous Ethernet (SyncE) which allows transport of clock signals through the Ethernet physical layer. This prevents the clock skew and clock jitter between adjacent network nodes. In this talk, Michał and Arkadiusz will motivate us with the need of frequency synchronization and its role when coupled with PTP in 5G/6G networks. They will discuss the open-source project synce4l [0] and demonstrate, focusing mainly on the features, requirements (both in software and hardware), and configuration in a real network. Finally, the talk will describe how synce4l corresponds with the currently discussed new DPLL (Digital Phase Locked Loop) subsystem [1] in the Linux kernel and user-space networking community. [0] https://github.com/intel/synce4l [1] https://lore.kernel.org/netdev/20230824213132.827338-1-vadim.fedorenko@linu… cheers, jamal Reminder: Three days to go before early-bird registration ends!

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0x17: Talk, Unstoppable Session Layer
by Jamal Hadi Salim 04 Oct '23

04 Oct '23

Back in circa 0x15[0], Alex Aring asked if you have an ECONNRESET on your socket, and even recovered, should we consider the communication reliable? Back then Alex made the argument that when an application encounters connection errors, the act of merely reconnecting reduces the likelihood of the application being considered reliable. He suggested a session layer to help in improving the reliability. To build up on that experience, Alex is back with what he calls "Unstoppable Session Layer" (USL) to allow you to easily switch your networking application to provide a session layer between application and transport layer. This talk will show how to easily put such a session layer on your networking application. It will be demonstrated by a basic TCP ping-pong application while tcpkill [1] tries to run crazy and interfere with the TCP application by sending TCP resets. The eventual goal is to port this implementation into the kernel so that that applications can benefit from it. [0] https://netdevconf.info/0x15/session.html?ECONNRESET-on-a-reliable-socket-a… [1] https://en.wikipedia.org/wiki/Tcpkill cheers, jamal Reminder: Three days to go before early-bird registration ends!

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0x17: talk, Using eBPF to inject IPv6 Extension Headers
by Jamal Hadi Salim 04 Oct '23

04 Oct '23

IPv6 Extension Headers (EH) allows the IPv6 to be more flexible and extensible. Justin Iurman et al say, unfortunately, the EH does not survive easily on the global internet and it is often tricky to analyze these losses without real deployment; and for this reason they built an eBPF instrumented tool based that operators can use to test the survivability of specific IPv6 EHs. The tool can inject any of the extension headers (Hop-by-Hop Options Header, Destination Options Header, Routing Header, the Fragment Header, etc). The talk will go into the details of both the kernel and user space architecture and code of the tool. Justin will further demonstrate its potential usage through a use case deployed by a network service provider. cheers, jamal Reminder: Three days to go before early-bird registration ends!

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0x17: talk, Quantum-Proofing Data: The Power Of Post-Quantum Cryptography
by Jamal Hadi Salim 04 Oct '23

04 Oct '23

Quantum computing presents a potential threat of being able to compromise existing cryptographic techniques. Shor's algorithm has the potential to break the RSA and Elliptic Curve Diffie-Hellman algorithms, both of which are pivotal for key exchange in Transport Layer Security (TLS). Our speaker, Milena Olech, says the solution is to adopt post-quantum cryptography (PQC) algorithms. In this talk Milena outlines the mathematical foundation of the CRYSTALS-Kyber algorithm and illustrates its application in the TLS handshake. In order to assess the efficacy of PQC, Milena will detail a comprehensive comparison between traditional cryptographic methods and post-quantum alternatives and provide a condensed summary of the comparison. cheers, jamal Reminder: Three days to go before early-bird registration ends!

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Register now please!
by Jamal Hadi Salim 03 Oct '23

03 Oct '23

Just a reminder 5 more days to go for early bird registration. Also a reminder this is a hybrid conference; nothing can beat physical get together but you can participate virtually as well. Early registration helps us plan better. See: https://netdevconf.info/0x17/pages/registration.html cheers, jamal

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0x17: talk, Integrating eBPF Into The P4TC Datapath
by Jamal Hadi Salim 03 Oct '23

03 Oct '23

P4TC was first introduced in 0x16[1]. After the first RFC was posted on the list, some of the community feedback made was to convert the s/w datapath from a scriptable (ala tc u32) to instead make use of eBPF with a strong argument being made that the s/w data path will be more performant. In this talk Jamal Hadi Salim et al will discuss the new architecture which factors in eBPF as the software datapath. The talk will go into the P4TC architecture factoring in eBPF and the pros and cons of this change from a scriptable approach. Jamal (twit that horn here) will further discuss the uapi and the kernel code architecture. There have been several RFC postings in the last 9 months[2] and it is expected the upstreaming efforts will start in the near future. cheers, jamal [1]https://netdevconf.info/0x16/session.html?Your-Network-Datapath-Will-Be-P4-Scripted [2] latest at this posting can be found here: https://lore.kernel.org/netdev/20230930143542.101000-1-jhs@mojatatu.com/

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0x17: talk, Firewall and Service Tickets (FAST)
by Jamal Hadi Salim 03 Oct '23

03 Oct '23

There is no good standardized way for applications to signal the network for services, like QoS, that the app wants applied to their packets. Typically it is some sys admin that decides how these services and resources are partitioned and configures their control. Enter FAST - which is being developed at the IETF. Tom Herbert says FAST is secure, expressive, stateless, not spoofable, deployable, efficient, dynamic, requires no DPI, doesn’t disclose internals of the network, and works with any transport protocol. FAST tickets are attached to packets to describe the service requests and grants of admission that the application has requested from the network. Tickets are sent in IPv6 Hop-by-Hop options. Tom will provide rationale why Hop-by-Hop options are really the best choice compared to proposed alternatives despite concerns about them being dropped in the Internet. Eventually Tom will present the kernel patches and tie them to how applications will use the provided infra to request for tickets and how they are granted, how they're set and transmitted in packets, how a network node can process the FAST ticket in the packet and apply network mechanisms to satisfy the service requests. cheers, jamal PS: 5 more days left for early-bird registration. visit netdevconf.info/0x17/registration

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