|By Marten Terpstra||
|January 23, 2014 09:30 AM EST||
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.
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.
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.
SYS-CON Events announced today that SOA Software, an API management leader, will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. SOA Software is a leading provider of API Management and SOA Governance products that equip business to deliver APIs and SOA together to drive their company to meet its business strategy quickly and effectively. SOA Software’s technology helps businesses to accelerate their digital channels with APIs, drive partner adoption, monetize their assets, and achieve a...
Oct. 31, 2014 07:15 PM EDT Reads: 2,148
SYS-CON Events announced today that Aria Systems, the recurring revenue expert, has been named "Bronze Sponsor" of SYS-CON's 15th International Cloud Expo®, which will take place on November 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Aria Systems helps leading businesses connect their customers with the products and services they love. Industry leaders like Pitney Bowes, Experian, AAA NCNU, VMware, HootSuite and many others choose Aria to power their recurring revenue business and deliver exceptional experiences to their customers.
Oct. 31, 2014 06:30 PM EDT Reads: 2,221
SYS-CON Events announced today that AgilePoint, the leading provider of Microsoft-centric Business Process Management software, will exhibit at SYS-CON's 2nd International @ThingsExpo which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. AgilePoint is the leading provider of Microsoft-based Business Process Management (BPM) software products, has 1,300+ on-premise and cloud deployments in 25+ countries and provides the same advanced BPM feature set as J2EE vendors like IBM and Appian for the Microsoft .NET native environment. AgilePoint customer...
Oct. 31, 2014 05:00 PM EDT Reads: 1,400
The Internet of Things (IoT) promises to evolve the way the world does business; however, understanding how to apply it to your company can be a mystery. Most people struggle with understanding the potential business uses or tend to get caught up in the technology, resulting in solutions that fail to meet even minimum business goals. In his session at Internet of @ThingsExpo, Jesse Shiah, CEO / President / Co-Founder of AgilePoint Inc., will show what is needed to leverage the IoT to transform your business. He will discuss opportunities and challenges ahead for the IoT from a market and tec...
Oct. 31, 2014 04:00 PM EDT Reads: 1,676
SYS-CON Events announced today that Utimaco will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Utimaco is a leading manufacturer of hardware based security solutions that provide the root of trust to keep cryptographic keys safe, secure critical digital infrastructures and protect high value data assets. Only Utimaco delivers a general-purpose hardware security module (HSM) as a customizable platform to easily integrate into existing software solutions, embed business logic and build s...
Oct. 31, 2014 03:00 PM EDT Reads: 1,989
One of the biggest challenges when developing connected devices is identifying user value and delivering it through successful user experiences. In his session at Internet of @ThingsExpo, Mike Kuniavsky, Principal Scientist, Innovation Services at PARC, will describe an IoT-specific approach to user experience design that combines approaches from interaction design, industrial design and service design to create experiences that go beyond simple connected gadgets to create lasting, multi-device experiences grounded in people’s real needs and desires.
Oct. 31, 2014 02:00 PM EDT Reads: 1,861
The Internet of Things will greatly expand the opportunities for data collection and new business models driven off of that data. In her session at Internet of @ThingsExpo, Esmeralda Swartz, CMO of MetraTech, will discuss how for this to be effective you not only need to have infrastructure and operational models capable of utilizing this new phenomenon, but increasingly service providers will need to convince a skeptical public to participate. Get ready to show them the money! Speaker Bio: Esmeralda Swartz, CMO of MetraTech, has spent 16 years as a marketing, product management, and busin...
Oct. 31, 2014 09:00 AM EDT Reads: 2,368
SYS-CON Events announced today that TeleStax, the main sponsor of Mobicents, will exhibit at Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. TeleStax provides Open Source Communications software and services that facilitate the shift from legacy SS7 based IN networks to IP based LTE and IMS networks hosted on private (on-premise), hybrid or public clouds. TeleStax products include Restcomm, JSLEE, SMSC Gateway, USSD Gateway, SS7 Resource Adaptors, SIP Servlets, Rich Multimedia Services, Presence Services/RCS, Diame...
Oct. 31, 2014 09:00 AM EDT Reads: 1,735
Samsung VP Jacopo Lenzi, who headed the company's recent SmartThings acquisition under the auspices of Samsung's Open Innovaction Center (OIC), answered a few questions we had about the deal. This interview was in conjunction with our interview with SmartThings CEO Alex Hawkinson. IoT Journal: SmartThings was developed in an open, standards-agnostic platform, and will now be part of Samsung's Open Innovation Center. Can you elaborate on your commitment to keep the platform open? Jacopo Lenzi: Samsung recognizes that true, accelerated innovation cannot be driven from one source, but requires a...
Oct. 31, 2014 09:00 AM EDT Reads: 3,414
Things are being built upon cloud foundations to transform organizations. This CEO Power Panel at 15th Cloud Expo, moderated by Roger Strukhoff, Cloud Expo and @ThingsExpo conference chair, will address the big issues involving these technologies and, more important, the results they will achieve. How important are public, private, and hybrid cloud to the enterprise? How does one define Big Data? And how is the IoT tying all this together?
Oct. 31, 2014 08:45 AM EDT Reads: 2,038
We certainly live in interesting technological times. And no more interesting than the current competing IoT standards for connectivity. Various standards bodies, approaches, and ecosystems are vying for mindshare and positioning for a competitive edge. It is clear that when the dust settles, we will have new protocols, evolved protocols, that will change the way we interact with devices and infrastructure. We will also have evolved web protocols, like HTTP/2, that will be changing the very core of our infrastructures. At the same time, we have old approaches made new again like micro-services...
Oct. 31, 2014 07:00 AM EDT Reads: 1,717
SYS-CON Events announces a new pavilion on the Cloud Expo floor where WebRTC converges with the Internet of Things. Pavilion will showcase WebRTC and the Internet of Things. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices--computers, smartphones, tablets, and sensors – connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades.
Oct. 30, 2014 05:30 PM EDT Reads: 2,248
The only place to be June 9-11 is Cloud Expo & @ThingsExpo 2015 East at the Javits Center in New York City. Join us there as delegates from all over the world come to listen to and engage with speakers & sponsors from the leading Cloud Computing, IoT & Big Data companies. Cloud Expo & @ThingsExpo are the leading events covering the booming market of Cloud Computing, IoT & Big Data for the enterprise. Speakers from all over the world will be hand-picked for their ability to explore the economic strategies that utility/cloud computing provides. Whether public, private, or in a hybrid form, clo...
Oct. 30, 2014 05:30 PM EDT Reads: 1,572
SYS-CON Events announced today that Gridstore™, the leader in software-defined storage (SDS) purpose-built for Windows Servers and Hyper-V, will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Gridstore™ is the leader in software-defined storage purpose built for virtualization that is designed to accelerate applications in virtualized environments. Using its patented Server-Side Virtual Controller™ Technology (SVCT) to eliminate the I/O blender effect and accelerate applications Gridsto...
Oct. 30, 2014 02:00 PM EDT Reads: 2,647
SYS-CON Events announced today that Red Hat, the world's leading provider of open source solutions, will exhibit at Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Red Hat is the world's leading provider of open source software solutions, using a community-powered approach to reliable and high-performing cloud, Linux, middleware, storage and virtualization technologies. Red Hat also offers award-winning support, training, and consulting services. As the connective hub in a global network of enterprises, partners, a...
Oct. 30, 2014 12:15 PM EDT Reads: 2,100
As the Internet of Things unfolds, mobile and wearable devices are blurring the line between physical and digital, integrating ever more closely with our interests, our routines, our daily lives. Contextual computing and smart, sensor-equipped spaces bring the potential to walk through a world that recognizes us and responds accordingly. We become continuous transmitters and receivers of data. In his session at Internet of @ThingsExpo, Andrew Bolwell, Director of Innovation for HP’s Printing and Personal Systems Group, will discuss how key attributes of mobile technology – touch input, senso...
Oct. 30, 2014 12:00 PM EDT Reads: 1,798
The Internet of Things (IoT) is making everything it touches smarter – smart devices, smart cars and smart cities. And lucky us, we’re just beginning to reap the benefits as we work toward a networked society. However, this technology-driven innovation is impacting more than just individuals. The IoT has an environmental impact as well, which brings us to the theme of this month’s #IoTuesday Twitter chat. The ability to remove inefficiencies through connected objects is driving change throughout every sector, including waste management. BigBelly Solar, located just outside of Boston, is trans...
Oct. 30, 2014 11:00 AM EDT Reads: 2,218
Connected devices and the Internet of Things are getting significant momentum in 2014. In his session at Internet of @ThingsExpo, Jim Hunter, Chief Scientist & Technology Evangelist at Greenwave Systems, will examine three key elements that together will drive mass adoption of the IoT before the end of 2015. The first element is the recent advent of robust open source protocols (like AllJoyn and WebRTC) that facilitate M2M communication. The second is broad availability of flexible, cost-effective storage designed to handle the massive surge in back-end data in a world where timely analytics...
Oct. 30, 2014 08:00 AM EDT Reads: 1,687
Internet of @ThingsExpo Silicon Valley announced on Thursday its first 12 all-star speakers and sessions for its upcoming event, which will take place November 4-6, 2014, at the Santa Clara Convention Center in California. @ThingsExpo, the first and largest IoT event in the world, debuted at the Javits Center in New York City in June 10-12, 2014 with over 6,000 delegates attending the conference. Among the first 12 announced world class speakers, IBM will present two highly popular IoT sessions, which will take place November 4-6, 2014 at the Santa Clara Convention Center in Santa Clara, Calif...
Oct. 30, 2014 07:30 AM EDT Reads: 2,330
From a software development perspective IoT is about programming "things," about connecting them with each other or integrating them with existing applications. In his session at @ThingsExpo, Yakov Fain, co-founder of Farata Systems and SuranceBay, will show you how small IoT-enabled devices from multiple manufacturers can be integrated into the workflow of an enterprise application. This is a practical demo of building a framework and components in HTML/Java/Mobile technologies to serve as a platform that can integrate new devices as they become available on the market.
Oct. 29, 2014 02:15 PM EDT Reads: 2,097