Ethernet

Ultra-Scale Breakthrough for Containers & Neural-Class Networks

scottcschweitzer Containers , , , , ,

Large Container Environments Need Connectivity for 1,000s of Micro-services

DockerContainer

An epic migration is underway from hypervisors and virtual machines to containers and micro-services.  The motivation is simple, there is far less overhead with containers and the payback is huge. You get more apps per server as host operating systems, multiple guest operating systems, and hypervisors are replaced by a single operating system. Solarflare is seeking to advance the development of networking for containers. Our goal is to provide the best possible performance, with the highest degree of connectivity, and easiest-to-deploy NICs for containers.

Solarflare’s first step in addressing the special networking requirements of containers is the delivery of the industry’s first Ethernet NIC with “ultra-scale connectivity.” This line of NICs has the ability to establish virtual connections from a container microservice to thousands of other containers and microservices. Ultra-scale network connectivity eliminates the performance penalty of vSwitch overhead, buffer copying, and Linux context switching. It provides application servers the capacity to provide each micro-service with a dedicated network link. This ability to scale connectivity is critical to the success of deploying large container environments within a data center, across multiple data centers, and multiple global regions.

Neural-Class Networks Require Ultra-Scale Connectivity

A “Neural Network” is a distributed, scale-out computing model that enables AI deep learning which is emerging as the core of next-gen applications software. Deep learning algorithms use huge neural networks, consisting of many layers of neurons (servers), to process massive amounts of data for instant facial, and voice recognition, language translation, and hundreds of other AI applications.

“Neural-class“ networks are computing environments which may not be used for artificial intelligence, but share the same distributed scale-out architecture, and massive size. Neural-class networks can be found in the data centers of public cloud service providers, stock exchanges, large retailers, insurance providers, and carriers, to name a few. These neural-class networks need ultra-scale connectivity. For example, in a typical neural-class network, a single 80-inch rack houses 38 dual-processor servers, each server with 10 dual-threaded cores, for a total of 1,520 threads. In this example, in order for each thread to work together on a deep learning or trading algorithm without constant Linux context switching, virtual network connections are needed to over 1,000 other threads in the rack.

Solarflare XtremeScale™ Family of Software-Defined NICs

XtremeScale Software-Defined NICs from Solarflare (SFN8000 series) are designed from the ground-up for neural-class networks. The result is a new class of Ethernet adapter with the ultra-high-performance packet processing and connectivity of expensive network processors, and the low-cost and power of general purpose NICs. There are six capabilities needed in neural-class networks which can be found only in XtremeScale software-defined NICs:

  1. Ultra-High Bandwidth – In 2017, Solarflare will provide high-frequency trading, CDN and cloud service provider applications with port speeds up to 100Gbps, backed by “cut-through” technology establishing a direct path between VMs and NICs to improve CPU efficiency.
  2. Ultra-Low Latency – Data centers are distributed environments with thousands of cores that need to constantly communicate with each other. Solarflare kernel bypass technologies provide sub-one microsecond latency with industry standard TCP/IP.
  3. Ultra-Scale Connectivity – A single densely-populated server rack easily exceeds over 1,000 cores. Solarflare can interconnect the cores to each other for distributed applications with NICs supporting 2,048 virtual connections.
  4. Software-Defined – Using well-defined APIs, network acceleration, monitoring, and security can be enabled and tuned, for thousands of separate vNIC connections, with software-defined NICs from Solarflare.
  5. Hardware-Based Security – Approximately 90% of network traffic is within a data center. With thousands of servers per data center, Solarflare can secure entry to each server with hardware-based firewalls.
  6. Instrumentation for Telemetry – Network acceleration, monitoring and hardware security is made possible by a new class of NIC from Solarflare which captures network packets at line speeds up to 100Gbps.

In May Solarflare will release a family of kernel bypass libraries called Universal Kernel Bypass (UKB). This starts with an advanced version of DPDK providing packets directly from the NIC to the container to several versions of Onload which provide higher level sockets connections from the NIC directly to containers.

 

RoCE vs TCP for Low-Latency Apps

scottcschweitzer networking , , , , ,

rocelogoThe effectiveness of our communication as a species is one of our defining characteristics. Earlier this week while waiting in a customer’s lobby in Chicago I noticed four framed posters displaying all the hand signals used in the trading pits of four major markets. Having been focused on electronic trading for the past decade this “ancient” form of communications became an instant curiosity worthy of inspection. On reflection, I was amazed to think that trillions of dollars in transactions over decades had been conducted purely by people motioning with their hands.

About a decade ago in the High-Performance Computing (HPC) market, a precursor market for High-Frequency Trading (HFT), there was a dust-up regarding the effectiveness of Remote Direct Memory Access (RDMA). One of Myricom’s senior researchers wrote an article for HPCWire titled “A Critique of RDMA” that set off a chain reaction of critical response articles:

At the time Myricom was struggling to establish relevance for its new Myrinet-10G protocol against a competing technology, Infiniband, which was rapidly gaining traction. Now to be fair, at the time I was in sales at Myricom. The crux of the article was that the one-sided RDMA communications model, which rose from the ashes of the Virtual Interface Architecture (VIA), was still more of a problem than a solution when compared to the existing two-sided Send/Recv model used by four other competing HPC protocols (QsNet, SeaStar, Infinipath & Myrinet Express).

Now RDMA has had a decade to improve as it spread from Infiniband to Ethernet under the name RDMA over Converged Ethernet (RoCE), but it still has performance issues. The origin of RDMA is cast in a closed lossless layer-2 Infiniband network with deterministic latency. Let’s take a moment and adopt a NASCAR analogy. Think of RDMA as the vehicle and Infiniband as the track. One can take a Sprint Cup Series vehicle tuned for the Charlotte Motor Speedway, and take it for a spin on the local roads, but is that really practical (it certainly isn’t legal)? Yes, its origin is in the stock car, but how well will it do in stop and go traffic, particularly on uphill grades? How about parallel parking, oh wait there’s no reverse. Tight turns at low speeds, signaling, weather, etc. Sprint Cup Series vehicles are designed for 200MPH on a closed extremely well defined and maintained course. Ethernet, by contrast, is the road driven by everyone else, it’s unpredictable with thousands of obstacles, and is ever changing.

Those familiar with Ethernet know that lossless and deterministic latency are not two characteristics often normally associated with this network fabric. Some of us have been around the block and lived through Carrier Sense Multiple Access with Collision Detection (CSMA/DA) where packets often collided and random delays before retransmission attempts were common. TCP/IP was developed during these early days and it was designed with this packet loss as a key criterion. In the past three decades Ethernet has evolved considerably from its roots as a shared coax cable utilizing vampire taps to where we are today with dedicated twisted pair cabling and fiber optics, but on rare occasion, packets are still dropped, and performance isn’t always deterministic. Today most packet drops are as a result of network congestion. As discussed TCP/IP is equipped to handle this, unfortunately, RoCE is not.

For RoCE to perform properly it requires a lossless layer-2 network. Essentially a NASCAR track overlaid onto our public roads. To accomplish this over a routed Ethernet network a new protocol was developed: Data Center Bridging Capabilities Exchange (shortened to DCB or DCBX). DCB is used at every hop of the network to negotiate and create a lossless layer-2 fabric on top of Ethernet. It achieves this by more tightly managing queue overflows and by adjusting network flow priorities as if they were traversing separate physical media. In essence RoCE traffic is prioritized into essentially its own carpool lane ahead of other traffic in hopes of avoiding drops as a result of congestion. While this all sounds great, in talking with several large Web2.0 customers who’ve invested years in RoCE we learned that the vast number will never deploy it in production. There are far too many challenges to get and keep it working, and in high traffic volumes, it suffers. Unlike Infiniband HPC clusters which are stood up as self-contained networks (closed course race tracks) to address specific computational problems, Ethernets are in a constant state of flux with servers and switches being added and removed (our public road system) as the needs of the business change. To be clear TCP/IP is resilient to packet loss, while RoCE is not.

On the latency performance side of things, in the past decade, we’ve achieved roughly one microsecond for a 1/2 round trip (a send + receive) with both TCP and UDP, when using Solarflare’s OpenOnload. This is in line with RoCE latency which is also in the domain of one microsecond. Keep in mind that normal TCP or UDP transactions over 10GbE typically run in the range of 5 to 15 microseconds, so 1 microsecond is a huge improvement. By now you’re likely saying “So what?” For most applications like file sharing, databases, etc… the difference between one microsecond and even fifteen microseconds is lost in the 10,000+ microseconds a whole transaction might take. It turns out though that there are new breeds of network latency-sensitive applications that depend on technologies like Non-Volatile Memory Express (NVMe), Neural Networks, and high volume compound web transactions that can see significant improvements when latency is reduced. When low latency TCP is applied to these problems the performance gains are both measurable and significant.

So the next time someone suggests RoCE ask if they’ve considered a little known competing protocol called TCP/IP. While RoCE is the shiny new object, TCP/IP has had several decades of innovation behind it which explains why it’s the underlying “language of the Internet”. Consider asking those promoting RoCE what their porting budget is, and if they’ve factored in the cost of the new network switches that will be required to support DCB? It’s very likely that the application they want to deploy already supports TCP/IP, and if latency and throughput are key factors then consider contacting Solarflare about OpenOnload. OpenOnload accelerates existing sockets based applications without having to modify them.

The Fifth wave in the 10GbE Market

scottcschweitzer networking ,

In 2003 we saw the emergence of the 10GbE server adapter market with only several implosionplayers, we’ll call this the first wave. Early products by Neterion and Intel carried extremely high price tags, often approaching $10K. This lead to a flood of companies jumping into the market in an effort to secure an early mover advantage. High-Performance Computing (HPC) companies like Myricom with it’s Myrinet 2G, and Mellanox with Infiniband SDR 10G was viewed by some as possibly having a competitive advantage as they’d already developed silicon in this area. In August of 2005, I joined Myricom to help them transition from HPC to the wider Ethernet market. By March of 2006, we launched a single port 10GbE product with a $595 price point, three years accompanied by a 10X drop in market price. That year the 10GbE market had grown to 18 different companies all offering 10GbE server adapters, we’ll consider this the second wave. In my 2013 article “Crash & Boom: Inside the 10GbE Adapter Market” I explored what had happened up to that point to take the market from 18 players down to 10, you guessed it the third wave. Today only six companies remain who are actually advancing the Ethernet Controller market forward, and this is perhaps the fourth wave.

Intel is the dominant 10GbE adapter market player. They are viewed by many as the commodity option who checks the majority of the feature boxes while delivering reasonable performance. Both Mellanox and QLogic are the exascale players as their silicon carries Infiniband specific features which they’ve convinced this market are important. In storage Chelsio rules as they’ve focused considerable silicon towards offloading the computational requirements of iSCSI. For the low latency and performance over BSD compliant TCP and UDP sockets sought by the financial traders of the world, Solarflare is king. This leaves one remaining actor, Broadcom, and in fact, they were acquired by Avago who also picked up Emulex. The word is they’ve dramatically cut their Ethernet controller development staff right after having completed their 25GbE controller ASIC, which may be why we’ve not seen it reach the market.

So as the 10GbE market sees feature & performance gains as the silicon is migrated over the next several years to 25GbE and 50GbE expect to continue seeing these four players dominate in their respective niches: Intel, Mellanox, Qlogic, Solarflare & Chelsio. I view this final phase as the fifth wave.

1.44 us Full Round Trip Latency, Unlikely

scottcschweitzer HFT , , ,

Tuesday morning one of the guys on my team woke me with a text stating a competitor was claiming 1.44 microseconds for a full round trip (RT) using UDP.  Two things about this immediately struck me as strange: first it was reported as a full round trip number, and second, the number (excluding units) was oddly close to what I’d thought the theoretical 1/2 RT limit might be. You see in the ultra-low latency, high-frequency trading market, time is everything. One need only be a few nanoseconds faster than their competition to win the lion’s share of the business. So speed is everything, but in the end, physics sets the speed limit.

In an ideal world if one were to measure the time required for a UDP packet to enter a network server adapter, traverse the Ethernet controller chip, travel the host PCIe bus, through the Intel CPU complex and finally end up in memory they’d find that this journey was roughly 730 nanoseconds. Now it should be noted that this varies across Intel server families & clock rates. We could be off by as much as +/- 100 nanoseconds, measuring at this level is pretty challenging, but 730 nanoseconds is a reasonable number to start with. Also, it should be noted that this is with Solarflare’s current 7000 series Ethernet Controller ASIC.

Breaking this down further, the most expensive part of this trip is the 500 nanoseconds or so the UDP packet will spend in Solarflare’s Ethernet controller chip. This chip is arguably the most popular low latency Ethernet Controller ASIC on the market today, it includes a high-performance PHY layer, an L2 switch, and built-in PCIe controller logic, everything happens within this single chip.  Over 1,000 financial trading firms rely on this technology daily, most of the world’s financial exchanges and nearly all of their high-performance customers depend on Solarflare, and as such they’ve turned all the dials possible to squeeze out every available nanosecond. Add to this 150 nanoseconds, the time the packet will spend traveling across the PCIe bus using DMA to cache via DDIO (not RAM), and finally another 80 nanoseconds or so to store it in RAM, making your final total 730 nanoseconds to receive a packet to memory. Again, your mileage will vary considerably so please only use these numbers as rough reference points. For a 1/2RT you’ll need to double this number (a receive plus a send) which brings the 1/2RT total to 1,460 nanoseconds, or 1.46 microseconds. It should also be noted that receives and sends have different costs, sends often consume less time, so again your numbers will vary, and this number should, in fact, be smaller. That’s Solarflare physics.  Solarflare has a new 8000 series Ethernet Controller ASIC coming out soon which will further trim down the 500 nanoseconds spent in the ASIC, but by exactly how much is still a closely guarded secret.

So is 1.44 microseconds for a conventional (through to user space vs. done completely in an FPGA) full round trip possible today? Well, the PCIe and memory components of this total 920 nanoseconds (150 nanoseconds for the PCIe bus plus 80 nanoseconds for CPU to memory, and both times 4 to address a full round trip). This leaves 520 nanoseconds to traverse the Ethernet Controller logic four times, or 130 nanoseconds for each pass. Considering that the most popular low-latency Ethernet controller chip on the planet requires 500 nanoseconds, doing it in 130 nanoseconds with the same degree of utility is highly unlikely.

On checking this competitor’s data sheet for this product we found that they have documented 1.82 microseconds for a UDP 1/2RT using 64-byte packets. Compare this to the 1.44 microseconds they claimed verbally for a full round trip, and one could see that they’ve significantly stretched the truth. If it sounds too good to be true, it probably is…