Welcome!

FinTech Journal Authors: Yeshim Deniz, Pat Romanski, Rajeev Kozhikkattuthodi, Elizabeth White, Jason Bloomberg

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
SYS-CON Events announced today that IBM has been named “Diamond Sponsor” of SYS-CON's 21st Cloud Expo, which will take place on October 31 through November 2nd 2017 at the Santa Clara Convention Center in Santa Clara, California.
When growing capacity and power in the data center, the architectural trade-offs between server scale-up vs. scale-out continue to be debated. Both approaches are valid: scale-out adds multiple, smaller servers running in a distributed computing model, while scale-up adds fewer, more powerful servers that are capable of running larger workloads. It’s worth noting that there are additional, unique advantages that scale-up architectures offer. One big advantage is large memory and compute capacity...
In his session at @ThingsExpo, Eric Lachapelle, CEO of the Professional Evaluation and Certification Board (PECB), provided an overview of various initiatives to certify the security of connected devices and future trends in ensuring public trust of IoT. Eric Lachapelle is the Chief Executive Officer of the Professional Evaluation and Certification Board (PECB), an international certification body. His role is to help companies and individuals to achieve professional, accredited and worldwide re...
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend 21st Cloud Expo October 31 - November 2, 2017, at the Santa Clara Convention Center, CA, and June 12-14, 2018, at the Javits Center in New York City, NY, and learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
No hype cycles or predictions of zillions of things here. IoT is big. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, Associate Partner at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He discussed the evaluation of communication standards and IoT messaging protocols, data analytics considerations, edge-to-cloud tec...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assista...
Artificial intelligence, machine learning, neural networks. We’re in the midst of a wave of excitement around AI such as hasn’t been seen for a few decades. But those previous periods of inflated expectations led to troughs of disappointment. Will this time be different? Most likely. Applications of AI such as predictive analytics are already decreasing costs and improving reliability of industrial machinery. Furthermore, the funding and research going into AI now comes from a wide range of com...
SYS-CON Events announced today that CA Technologies has been named "Platinum Sponsor" of SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business - from apparel to energy - is being rewritten by software. From planning to development to management to security, CA creates software that fuels transformation for companies in the applic...
Multiple data types are pouring into IoT deployments. Data is coming in small packages as well as enormous files and data streams of many sizes. Widespread use of mobile devices adds to the total. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists looked at the tools and environments that are being put to use in IoT deployments, as well as the team skills a modern enterprise IT shop needs to keep things running, get a handle on all this data, and deliver...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. 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 devic...
SYS-CON Events announced today that Cloud Academy named "Bronze Sponsor" of 21st International Cloud Expo which will take place October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara, CA. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud com...
SYS-CON Events announced today that Enzu will exhibit at SYS-CON's 21st Int\ernational Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their ...
We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA
SYS-CON Events announced today that GrapeUp, the leading provider of rapid product development at the speed of business, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company, specialized in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market acr...
SYS-CON Events announced today that Ayehu will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara California. Ayehu provides IT Process Automation & Orchestration solutions for IT and Security professionals to identify and resolve critical incidents and enable rapid containment, eradication, and recovery from cyber security breaches. Ayehu provides customers greater control over IT infras...
SYS-CON Events announced today that MobiDev, a client-oriented software development company, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business...
In his session at Cloud Expo, Alan Winters, an entertainment executive/TV producer turned serial entrepreneur, presented a success story of an entrepreneur who has both suffered through and benefited from offshore development across multiple businesses: The smart choice, or how to select the right offshore development partner Warning signs, or how to minimize chances of making the wrong choice Collaboration, or how to establish the most effective work processes Budget control, or how to ma...
"When we talk about cloud without compromise what we're talking about is that when people think about 'I need the flexibility of the cloud' - it's the ability to create applications and run them in a cloud environment that's far more flexible,” explained Matthew Finnie, CTO of Interoute, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
IoT solutions exploit operational data generated by Internet-connected smart “things” for the purpose of gaining operational insight and producing “better outcomes” (for example, create new business models, eliminate unscheduled maintenance, etc.). The explosive proliferation of IoT solutions will result in an exponential growth in the volume of IoT data, precipitating significant Information Governance issues: who owns the IoT data, what are the rights/duties of IoT solutions adopters towards t...
With the introduction of IoT and Smart Living in every aspect of our lives, one question has become relevant: What are the security implications? To answer this, first we have to look and explore the security models of the technologies that IoT is founded upon. In his session at @ThingsExpo, Nevi Kaja, a Research Engineer at Ford Motor Company, discussed some of the security challenges of the IoT infrastructure and related how these aspects impact Smart Living. The material was delivered interac...