- people - netdevconf.info

0x14: nutsnbolts, The Path To TCP 4K MTU and RX ZeroCopy
by Jamal Hadi Salim 09 Feb '20

09 Feb '20

If you are a big shop like Google you are always looking to squeeze all the performance juice you can out of your CPUs. Given the large number of machines deployed, a 1% performance improvement could mean millions of $$ in savings in both capital and operational costs. In this talk, monsieur Eric Dumazet - the man sometimes refered to in passing as some form of ninja - will describe changes introduced by Google that help double TCP receiver efficiency in their datacentres. Eric will discuss various issues that had to be overcome and a variety of tuning that was needed to achieve these performance improvements. More info: https://netdevconf.info/0x14/session.html?talk-the-path-to-tcp-4k-mtu-and-r… cheers, jamal

1 0

0x14: nutsnbolts, What to do with 1/2 a bit? L4S, SCE, or ?
by Jamal Hadi Salim 08 Feb '20

08 Feb '20

Imagine you have only one more bit left in the world! Scratch that. Imagine there is only a half bit left in the world. Then imagine there are multiple causes vying for this half bit. Who would you give it to and why? Yes, these things happen;-> A lot easier when it is between developers and a lot harder when it is to decide a standard that shall be cast in stone. The Internet Engineering Task Force (ietf) Transport Area Working Group (tsvwg) has such a struggle going. There are presently 2 proposals before for the last unused code point in the IPv4/6 header - one by the Low Latency Low Loss Scalable throughput (L4S) folks (see Netdev 0x13 for L4S talks) and another from the Some Congestion Experienced (SCE) folks. In this talk, Rodney Grimes will describe the two solutions and their prototype kernel implementations; what changes are made to both TCP and IP layers, etc. Rod is then going to pose the $1M question and solicit feedback: is one approach better than the other or do we need a new outlook? More info: https://netdevconf.info/0x14/session.html?talk-what-to-do-with-half-a-bit-L… Reminder, registration is now open and early bird is still in effect. https://netdevconf.info/0x14/registration.html cheers, jamal

1 0

0x14: nutsnbolts, XDP in Open vSwitch
by Jamal Hadi Salim 07 Feb '20

07 Feb '20

Being able to marry new Linux technology with existing "legacy" infra is valuable to allow for continuity. XDP is a relatively new technology introduced in Linux networking which enables more efficient packet processing. A common desire is to allow "legacy" packet processing functions to take advantage of the speed advantages offered by XDP. In addition to the efficiency factor, XDP also provides a time-to-market advantage: new network packet processing features can be added without need to go through the complexity of the upstreaming process. Toshiaki Makita and William Tu are still in pursuit of getting openvswitch to use XDP. In this talk Toshiaki and William attempt to marry OVS to XDP via: 1. Attaching XDP from kernel through UMH (user mode helper), 2. Reusing TC HW acceleration interface 3. Attaching XDP from OVS userspace daemon The authors will describe their approaches and challenges faced. More info: https://netdevconf.info/0x14/session.html?talk-XDP-in-open-vswitch Reminder, registration is now open and early bird is still in effect. https://netdevconf.info/0x14/registration.html cheers, jamal

1 0

0x14: nutsnbolts, Using Upstream MPTCP in Linux Systems
by Jamal Hadi Salim 06 Feb '20

06 Feb '20

The Multipath TCP community started its engagement with netdev conf 0.1 (https://netdevconf.info/0.1/sessions/16.html) and have shown up to multiple other netdev confs after to solicit for feedback and report progress. After all that hard work MPTCP has finally been merged! In this talk Mat Martineau, Ossama Othman and Peter Krystad will provide advice to developers, ops and distros how to make good use of the upstreamed MPTCP. They will discuss kernel considerations, report on upstream merge progress to date, and introduce the Multipath TCP Daemon(mptcpd) to the Linux networking community. More info: https://netdevconf.info/0x14/session.html?talk-using-upstream-MPTCP-in-linu… Reminder, registration is now open and early bird is still in effect. https://netdevconf.info/0x14/registration.html cheers, jamal

1 0

0x14: nutsnbolts, Hardware offload for K8s container networking
by Jamal Hadi Salim 05 Feb '20

05 Feb '20

Kubernetes(k8s) Container Network Interface (CNI) is a specification for managing network resources on a kubernetes cluster. CNI enables plugin-based networking solution for containers ranging in functionality from IP address management to access control policy management, QOS, etc. Operators can pick and choose from the many packaged and open CNI implementations that exist or could create custom CNIs to serve their needs. In this talk Rony Efraim and Liel Shoshan describe how they approach hardware network offload enabling in k8s. Rony and Liel will illustrate offloading with a bunch of CNIs that can be used in conjunction with OVS. In addition, they will also describe how to offload for other K8s use cases like pod-to-pod intra networking and enhancing ingress service load balancing via dp_hash. And last but not least the speakers will describe challenges faced and future work. More info: https://netdevconf.info/0x14/session.html?talk-hardware-offload-for-k8s-con… Reminder, registration is now open and early bird is still in effect. https://netdevconf.info/0x14/registration.html cheers, jamal

1 0

0x14: nutsnbolts, Evaluation of TCP Congestion Control Algorithms over mmWave (5G) Mobile Networks
by Jamal Hadi Salim 05 Feb '20

05 Feb '20

As the commercials say - 5G(Fifth Generation) networking is here. Why is that a big deal? One appealing aspect: How do you like getting multi-gigabit bandwidth to your mobile device(s)? How does that work? For the first time in commercial mobile networking history a vast untapped spectrum has been made available for mass user consumption in the millimeter wave length range; in the 5G world it is refered to as "mmWave". The spectrum in mmWave links makes possible the multi-Gbps data rates on the 5G cellular networks. The problem with mmWave links is they are, like most high-frequency signals, susceptible to blockage. Basic obstructions like trees, snow, rain, buildings, etc interfere with the signal. A technique called beamforming helps but doesnt solve the problem entirely. To put this in context: Think of having a link that is very high speed but is constantly fluctuating in capacity. Then the question is: "How does TCP congestion control work in this kind of setup?" In this talk Feng Li, Jae Won Chung and Jamal Hadi Salim[1] will present results of a study to evaluate how various Linux TCP congestion control algorithm implementation fare over mmWave links. The authors claim this is _the first ever_ such study on a real commercial 5G network! The study was carried on the Verizon 5G deployment network. Feng et al will present data on comparing popular TCP congestion control algorithms, including NewReno, Cubic, BBR and BBRv2 (prepatch) etc. The results show that the performance of TCP on mmWave links is still highly dependent on the combination of TCP algorithm and socket buffer sizes. Without a doubt mmWave links impose new challenges on future transport layer design and the authors hope this talk will incentivize more discussions in the community. [1] Refered to in the third person. More info: https://netdevconf.info/0x14/session.html?talk-preliminary-evaluation-of-TC… Reminder, registration is now open and early bird is still in effect. https://netdevconf.info/0x14/registration.html cheers, jamal

1 0

0x14: nutsnbolts, It is Batching All the Way Down!
by Jamal Hadi Salim 04 Feb '20

04 Feb '20

It is turtles^wbatching all the way down folks! Several parts of the kernel network stack use batching for performance enhancement. Maciej Fijałkowski, Bjorn Topel and Krzysztof Kazimierczak feel we could do a little more. They borrow ideas from other high performance packet processing solutions, such as DPDK, and tweak those ideas to an "XDP first" design - meaning drivers that are optimized for the case when all packets are processed by XDP. In this talk, they describe how they enabled batching at both the driver and XDP level to improve performance for two sample drivers Intel i40e and ice. Maciej et all will share the performance improvements gained and propose some ideas how these batching ideas can equally be applied at other BPF hooks (socket send/recv, traffic control, etc) More info: https://netdevconf.info/0x14-staging/session.html?talk-it-is-batching-all-t… cheers, jamal

1 0

0x14: nutsnbolts, Reducing Kernel Queuing Delays with TCP Window Space Events
by Jamal Hadi Salim 04 Feb '20

04 Feb '20

Existing performance enhancing mechanisms such as TCP auto-tuning or programmatic async(epoll, etc) events such as "ready to send" help applications to sustain high throughput even under high Bandwith-Delay product scenarios. But: the folks at the Tor project have found that when you have thousands of active TCP sockets transmitting high volumes of data, many of which are simultenous (as it is the case in Tor anonymity network) then these mechanisms are insufficient. Local buffer bloat becomes a hindrance. In this talk, David Goulet and Rob Jansen introduce a new async event that helps applications overcome these issues. The new event supplements and extends the current write "ready to send" event that triggers when a socket buffer has free space. David and Rob will present data and go into more detailed description of the problem and then show the effect that such a change could have on performance through a small scale simulation. More info: https://netdevconf.info/0x14-staging/session.html?talk-reducing-kernel-queu… Reminder, registration is now open and early bird is still in effect. https://netdevconf.info/0x14/registration.html cheers, jamal

1 0

0x14: nutsnbolts, Time-travel Linux (network) simulation
by Jamal Hadi Salim 04 Feb '20

04 Feb '20

There are times when you want to recreate a network test that would typically take a while to complete. In addition, when you run the tests, you want the results to be consistent in different runs. In this talk, Johannes Berg and Richard Weinberger describe their solution to this requirement. They introduce a mechanism to do "time travel" in User Mode Linux(UML) with a virtual clock. The time travel mode allows for reproducible testing at significantly faster test execution times; as an example, on a relatively slow laptop: two simulated machines in such a setup can simulate 61 pings, at a default 1 second interval, in about 1.6 seconds real time (as opposed to 61 seconds). More info: https://netdevconf.info/0x14/session.html?talk-time-travel-linux-network-si… Reminder, registration is now open and early bird is still in effect. https://netdevconf.info/0x14/registration.html cheers, jamal

1 0

0x14: nutsnbolts, 5 years of iwd - lessons learned about Linux wireless subsystem
by Jamal Hadi Salim 03 Feb '20

03 Feb '20

The iNet Wireless Daemon aka iwd was created to be an alternative to wpa_supplicant. Iwd provides a more complete solution set for WiFi compared to wpa_supplicant - with a much longwe list of features. Marcel Holtmann will provide insights into iwd architecture and how it takes advantage of kernel features to provide good user experience. In addition, Marcel will go over lessons learned since inception of iwd in the last 5 years. More info: https://netdevconf.info/0x14/session.html?talk-5-years-of-iwd-lessons-learn… Reminder, registration is now open and early bird is still in effect. https://netdevconf.info/0x14/registration.html cheers, jamal

1 0