Welcome!

Cloud Security Authors: Waqar Ahmad, Liz McMillan, Elizabeth White, Derek Weeks, Dan Sarel

Related Topics: SDN Journal, Java IoT, Containers Expo Blog, @CloudExpo, Cloud Security, @BigDataExpo

SDN Journal: Blog Post

Stateless Transport Tunneling (STT) Meets the Network

At a high level the concepts of larger packets, hardware offload, reduced CPU load and interrupts all make sense

Last week I walked through the packet formats for VXLAN and NVGRE specifically focused on ways by which the overlay packets provide information to the physical network that help the physical network. Some of the initial extreme thoughts that the overlay and physical network can and should be completely ignorant of each other have softened more recently and more pragmatic thoughts of collaborating layers are being articulated. At Plexxi we have often mentioned that we believe the physical network and the overlay need to be closely orchestrated to get the most benefit out of the total network solution. And orchestration != ECMP.

In addition to VXLAN and NVGRE, Stateless Transport Tunneling (STT) is an encapsulation mechanism used by VMware, mostly for communication between server based vSwitches. It is a bit more involved and complicated than VXLAN and NVGRE, mostly because it was designed to carry large data packets, up to 64 Kbytes. Physical networks have limitations on the size of a packet that can be transferred. Ethernet standard maximum transmission unit (MTU) used to be 1500 bytes, but most ethernet devices these days can support jumbo packets allowing packets of 4, 9 or even 16 Kbytes in size. Even at those sizes, large data transfers are somewhat hampered by the work involved in taking a large chunk of data and then chopping them up into smaller portions to be transmitted. In a response to this, hardware vendors have taken some of this functionality and added it to the Network Interface Cards (NICs) on servers and have them do most of this segmentation and re-assembly work based on how TCP takes large portions of data and chops them into smaller segments. Doing his in hardware means it can be done faster, but more importantly, it removes this burden from the server CPUs, allowing them to do other (more useful) work.

STT was designed to make use of these TCP capabilities in NICs. STT can take ethernet packets up to 64 Kbytes from a VM on a server, and tunnel it to its destination as a 64 Kbyte entity. This STT frame has to be chopped into smaller pieces to match the MTU of the physical network, but an STT packet looks just like a TCP segment to the receiving NICs, allowing them to reconstruct the original 64 Kbyte packet without needing the CPU.

When the sending tunnel endpoint receives a large chunk of data to be transmitted at another VM at the other side of a tunnel, the vSwitch takes several steps to encapsulate this packet. First, it adds an STT Frame Header to the packet.

STT Frame Format 1

The STT Header is 18 bytes in length and has a variety of administrative fields, but the key field is the Context ID. This is a 64 bit field and its intended use is similar to the VXLAN Network Identifier (VNI) or the NVGRE Virtual Subnet ID (VSID). While the semantics of this field are somewhat defined, its value and how to use it is left open in the latest specifications. Its main purpose is to provide the receiving tunnel endpoint the information it needs to determine where this packet needs to be sent after decapsulation.

After the STT Frame Header has been added, this new packet (original packet  + new STT header) is chopped into smaller pieces so that each piece is at least 62 bytes smaller than the MTU of the physical network. Each of these new segments receives 24 byte TCP like header, a normal 20 byte IP header, and of course the final 18 byte Ethernet header before transmission. The magic (or ugliness for those less enamored by STT) is in the TCP like header. These 24 bytes are formatted just like a normal TCP header to ensure the hardware in the NICs can re-assemble segments that belong together. The traditional Acknowledgement field in TCP is used as a fragment ID, essentially telling the NIC that all packets/segments that come in with the same fragment ID belong together and should be reassembled into the larger original ethernet frame. The traditional Sequence number is used as an offset indicator, to tell the NIC in what order the fragments need to be put together.

STT Frame Format 2

Similar to VXLAN and NVGRE described last week, STT has a mechanism to create entropy for the physical network to distinguish flows from each other and allow them to be balanced using ECMP (or link aggregation – LAG) based deployments. In STT, the TCP source port is used to create entropy. The originating tunnel end point will use some hash calculation on the original packets header information and use the result to populate the TCP source port. Switches in the physical network can now use the TCP port information from the tunneled packet in their hash calculation for ECMP or LAG packet distribution.

While STT is likely to be more efficient than either VXLAN or NVGRE for the transfer of large amount of information because it offloads the segmentation and re-assembly, it carries significantly more overhead than either VXLAN or NVGRE in additional header information for smaller packets. STT adds 80 bytes of new header to a VM originated ethernet packet for the first segment of this packet, 62 for each following segment. Compare that to a consistent 46 bytes for each NVGRE encapsulated packet, and 54 bytes for VXLAN. For traffic between VMs on the same server this may not matter, but it certainly does for traffic carried across the physical network. For the plentiful mice flows, we have likely doubled the size and bandwidth required for each.

A probably more significant drawback of STT comes from its strength. Designed for large packet transfers, once an original packet is encapsulated with STT header, chopped into parts, then encapsulated into individual ethernet, IP and TCP (like) headers, only the first packet provides any clue or context of the original source, destination, protocol, application and other content. The relevant pieces of that will only be found in the first segment, any follow up segments only provide enough information about the tunnel endpoints and no other original context without the first segment. And that makes debugging really hard. It also makes it hard to differentiate traffic on the physical network, even at a very high level Virtual Network identifier. And every existing network based service (realizing that one of the goals of overlay networks is to push this to the vSwitches themselves) will also have a hard time deciding what to do with these packets.

At a high level the concepts of larger packets, hardware offload, reduced CPU load and interrupts all make sense. But most data center ethernet networks can easily support 9k or even 16k packets, so perhaps the gap between 16k packet based transfer and 64k semi-stream based communication is really not that much considering that the bulk of packets are small to begin with (remember those mice and elephants?). Perhaps aligning the MTU of the virtual port with that of the network may be worthwhile to have the STT and original header in each and every packet on the wire. Regardless of whether that is a real wire, or a virtual one.

[Today's fun fact: One of the primary reasons the Mayflower pilgrims ended their voyage at Plymouth Rock was pretty much the same reason people today suspend their journeys: they ran out of beer. No need for a funny punch line on that one]

The post Stateless Transport Tunneling (STT) meets the Network appeared first on Plexxi.

Read the original blog entry...

More Stories By Marten Terpstra

Marten Terpstra is a Product Management Director at Plexxi Inc. Marten has extensive knowledge of the architecture, design, deployment and management of enterprise and carrier networks.

@ThingsExpo Stories
Join IBM June 8 at 18th Cloud Expo at the Javits Center in New York City, NY, and learn how to innovate like a startup and scale for the enterprise. You need to deliver quality applications faster and cheaper, attract and retain customers with an engaging experience across devices, and seamlessly integrate your enterprise systems. And you can't take 12 months to do it.
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, will discuss how research has demonstrated the value of Machine Learning in delivering next generation analytics to im...
This is not a small hotel event. It is also not a big vendor party where politicians and entertainers are more important than real content. This is Cloud Expo, the world's longest-running conference and exhibition focused on Cloud Computing and all that it entails. If you want serious presentations and valuable insight about Cloud Computing for three straight days, then register now for Cloud Expo.
You think you know what’s in your data. But do you? Most organizations are now aware of the business intelligence represented by their data. Data science stands to take this to a level you never thought of – literally. The techniques of data science, when used with the capabilities of Big Data technologies, can make connections you had not yet imagined, helping you discover new insights and ask new questions of your data. In his session at @ThingsExpo, Sarbjit Sarkaria, data science team lead ...
So, you bought into the current machine learning craze and went on to collect millions/billions of records from this promising new data source. Now, what do you do with them? Too often, the abundance of data quickly turns into an abundance of problems. How do you extract that "magic essence" from your data without falling into the common pitfalls? In her session at @ThingsExpo, Natalia Ponomareva, Software Engineer at Google, will provide tips on how to be successful in large scale machine lear...
IoT device adoption is growing at staggering rates, and with it comes opportunity for developers to meet consumer demand for an ever more connected world. Wireless communication is the key part of the encompassing components of any IoT device. Wireless connectivity enhances the device utility at the expense of ease of use and deployment challenges. Since connectivity is fundamental for IoT device development, engineers must understand how to overcome the hurdles inherent in incorporating multipl...
The IETF draft standard for M2M certificates is a security solution specifically designed for the demanding needs of IoT/M2M applications. In his session at @ThingsExpo, Brian Romansky, VP of Strategic Technology at TrustPoint Innovation, will explain how M2M certificates can efficiently enable confidentiality, integrity, and authenticity on highly constrained devices.
The paradigm has shifted. A Gartner survey shows that 43% of organizations are using or plan to implement the Internet of Things in 2016. However, not just a handful of companies are still using the old-style ad-hoc trial-and-error ways, unaware of the critical barriers, paint points, traps, and hidden roadblocks. How can you become a winner? In his session at @ThingsExpo, Tony Shan will present a methodical approach to guide the holistic adoption and enablement of IoT implementations. This ov...
We’ve worked with dozens of early adopters across numerous industries and will debunk common misperceptions, which starts with understanding that many of the connected products we’ll use over the next 5 years are already products, they’re just not yet connected. With an IoT product, time-in-market provides much more essential feedback than ever before. Innovation comes from what you do with the data that the connected product provides in order to enhance the customer experience and optimize busi...
Artificial Intelligence has the potential to massively disrupt IoT. In his session at 18th Cloud Expo, AJ Abdallat, CEO of Beyond AI, will discuss what the five main drivers are in Artificial Intelligence that could shape the future of the Internet of Things. AJ Abdallat is CEO of Beyond AI. He has over 20 years of management experience in the fields of artificial intelligence, sensors, instruments, devices and software for telecommunications, life sciences, environmental monitoring, process...
SYS-CON Events announced today that Ericsson has been named “Gold Sponsor” of SYS-CON's @ThingsExpo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. Ericsson is a world leader in the rapidly changing environment of communications technology – providing equipment, software and services to enable transformation through mobility. Some 40 percent of global mobile traffic runs through networks we have supplied. More than 1 billion subscribers around the world re...
SYS-CON Events announced today that Stratoscale, the software company developing the next generation data center operating system, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Stratoscale is revolutionizing the data center with a zero-to-cloud-in-minutes solution. With Stratoscale’s hardware-agnostic, Software Defined Data Center (SDDC) solution to store everything, run anything and scale everywhere...
Angular 2 is a complete re-write of the popular framework AngularJS. Programming in Angular 2 is greatly simplified – now it's a component-based well-performing framework. This immersive one-day workshop at 18th Cloud Expo, led by Yakov Fain, a Java Champion and a co-founder of the IT consultancy Farata Systems and the product company SuranceBay, will provide you with everything you wanted to know about Angular 2.
SYS-CON Events announced today that Men & Mice, the leading global provider of DNS, DHCP and IP address management overlay solutions, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. The Men & Mice Suite overlay solution is already known for its powerful application in heterogeneous operating environments, enabling enterprises to scale without fuss. Building on a solid range of diverse platform support,...
In his session at @ThingsExpo, Chris Klein, CEO and Co-founder of Rachio, will discuss next generation communities that are using IoT to create more sustainable, intelligent communities. One example is Sterling Ranch, a 10,000 home development that – with the help of Siemens – will integrate IoT technology into the community to provide residents with energy and water savings as well as intelligent security. Everything from stop lights to sprinkler systems to building infrastructures will run ef...
You deployed your app with the Bluemix PaaS and it's gaining some serious traction, so it's time to make some tweaks. Did you design your application in a way that it can scale in the cloud? Were you even thinking about the cloud when you built the app? If not, chances are your app is going to break. Check out this webcast to learn various techniques for designing applications that will scale successfully in Bluemix, for the confidence you need to take your apps to the next level and beyond.
Manufacturers are embracing the Industrial Internet the same way consumers are leveraging Fitbits – to improve overall health and wellness. Both can provide consistent measurement, visibility, and suggest performance improvements customized to help reach goals. Fitbit users can view real-time data and make adjustments to increase their activity. In his session at @ThingsExpo, Mark Bernardo Professional Services Leader, Americas, at GE Digital, will discuss how leveraging the Industrial Interne...
Whether your IoT service is connecting cars, homes, appliances, wearable, cameras or other devices, one question hangs in the balance – how do you actually make money from this service? The ability to turn your IoT service into profit requires the ability to create a monetization strategy that is flexible, scalable and working for you in real-time. It must be a transparent, smoothly implemented strategy that all stakeholders – from customers to the board – will be able to understand and comprehe...
Increasing IoT connectivity is forcing enterprises to find elegant solutions to organize and visualize all incoming data from these connected devices with re-configurable dashboard widgets to effectively allow rapid decision-making for everything from immediate actions in tactical situations to strategic analysis and reporting. In his session at 18th Cloud Expo, Shikhir Singh, Senior Developer Relations Manager at Sencha, will discuss how to create HTML5 dashboards that interact with IoT devic...
There is an ever-growing explosion of new devices that are connected to the Internet using “cloud” solutions. This rapid growth is creating a massive new demand for efficient access to data. And it’s not just about connecting to that data anymore. This new demand is bringing new issues and challenges and it is important for companies to scale for the coming growth. And with that scaling comes the need for greater security, gathering and data analysis, storage, connectivity and, of course, the...