|By Lori MacVittie||
|July 8, 2014 11:45 AM EDT||
One of the benefits of SDN is centralized control. That is, there is a single repository containing the known current state of the entire network. It is this centralization that enables intelligent application of new policies to govern and control the network - from new routes to user experience services like QoS. Because there is a single entity which has visibility into the state of the network as a whole, it can examine the topology at any given point and make determinations as to where this packet and that should be routed, how it is prioritized and even whether or not it is allowed to traverse the network.
It's a pretty powerful concept for networks, which traditionally distribute network state as individual configuration files across the data path.
Most of the focus of SDN is on the replacement of manual and scripted configuration methods with an API-driven mechanism. Whether that's OpenFlow or OpFlex or some other protocol is not really important as the benefit of operationalization is to provide a consistent interface from the perspective of the operator, not the device.
This is a real benefit; operationalization across operations and dev has proven to produce tangible benefits in the form of improved time to market and a reduction in errors. By centralizing network state in a controller, this model provides a comprehensive view of the network at any given moment. Because the controller is not just a repository but an active participant in the flow of data across the network, this visibility enables the controller to understand how to (ostensibly) non-disruptively change routes or apply new policies in real-time.
The benefit itself is not in question. What is in question is what happens when the controller of this new software-defined architecture becomes overwhelmed, and how to preserve that benefit when the centralized model must decentralize in order to scale.
The Eventually Consistent Problem Comes to the Network
Eventual consistency is nothing new. It has always been an issue when scaling applications, particularly those that rely on shared data. Consider Amazon, if you will. If you and I are both shopping for the same thing, and I order before you, it may take seconds or more before the database is updated. If you were in the middle of ordering at the same time, you and I may be contending for the same item. Because my order takes a moment or two to propagate through the system, your view of the database (the availability of the item) is inconsistent with mine.
It is assumed that eventually our views will be consistent, and that this age old unsolved problem of distributed computing simply must be accepted as unsolvable for now, Thus systems are designed with this principle in mind. Which means we end up back with Brewer's CAP Theorem staring us in the face and reminding us we can't be perfectly consistent in a distributed system, so we must deal with systems in such a way as to achieve eventually consistency.
At issue is the ability of a software controller to scale. The controller is, by design and necessity, part of the data path. That is both a blessing and a curse. It is from this fact that the real-time adaption of network behavior can be achieved, but it is also this fact which forces issues of scale and introduces the need for a distributed system from which the problem of eventual consistency derives. That's because more than one system will be the "master" repository for a given portion of network state. Even if one controller is designated as master of the network universe and thus maintains the "official" state of the network, there are those moments when the secondary (or tertiary) controller has modified the "official" state and introduces inconsistency. In the moments between when the two network states merge, there is the possibility that the first (master) controller will also try to make a decision based on information that relies on network state that is no longer valid. If Controller B, for example, removes a port from a VLAN, and before that state can propagate to the master, a packet arrives in the fabric, destined for that port, Controller A will have no way to know that it is no longer participating in the VLAN and will, as expected, tell the switch to route to that port.
The issue will be shortly resolved, assuming timely synchronization of network state across the cluster, but in the meantime performance (or availability) may be negatively impacted.
The problem with eventual consistency in the network is one of magnitude. Eventually consistent views of books in stock at Amazon has a very different impact than an eventually consistent view of the network underpinning today's applications and ultimately the business. We're not talking about losing out on a book, we're talking about potentially disrupting hundreds or thousands of applications that translates into hundreds of thousands or even millions of dollars. Ponemon's 2013 Cost of Data Center Outages proves this case out: "The average reported outage incident length was 86 minutes, resulting in average cost per incident of about $690,200."
Eventual consistency of the network may turn out to be quite costly.
Common Themes: Reliability and Control
This is not a new problem. This issue of stateful failover as applied to scalability of both infrastructure and applications is one that application delivery has been dealing with, well, for over a decade now. The issue when dealing with distributed state is always one of replication and synchronization between those devices providing for reliability. That doesn't change just because we move from one form factor to another, or from on-premise to cloud. The issue remains: how do we maintain an authoritative view of the state of an <application or network> while still enabling the scale necessary to meet demand?
While we (as in the industry "we") recognize that true stateful reliability - and thus perfect consistency - is currently unachievable due to the constraints of distributed system design, we also recognize that we can get pretty darn close. From an application perspective, the intelligence embedded in a service fabric is more than able to deal with the problem with minimal introduction of latency. That is, there will be a slight pause and some disruption when failure or disruption occurs in the network but if the service fabric is smart enough, the disruption is experienced by the end user as no more than a slight hiccup - likely unnoticeable.
But the further down the stack you go, toward core network function, the more disruptive such a hiccup is going to be.
That's one of the reasons a "centralized control, decentralized execution" architecture makes more sense from a network perspective. Such a model maintains authoritative control over the state of the network, but empowers individual components in the various fabrics (stateless L2-4 and stateful L4-7) that make up "the network" to maintain its own prescriptive configuration and take action when necessary based on the abstracted policies of the network as a whole.
Everyone likes to posit an answer to what will be the "killer app" for SDN. But before we can worry about that, we might want to consider what may be the "showstopper" obstacles for SDN. Eventual consistency when scaling controllers is one of those issues.
Because without a reliable and consistent network world, there is no application world. Or at least not one that users will be excited to rely on.
Internet of @ThingsExpo has announced today that Chris Matthieu has been named tech chair of Internet of @ThingsExpo 2017 New York The 7th Internet of @ThingsExpo will take place on June 6-8, 2017, at the Javits Center in New York City, New York. Chris Matthieu is the co-founder and CTO of Octoblu, a revolutionary real-time IoT platform recently acquired by Citrix. Octoblu connects things, systems, people and clouds to a global mesh network allowing users to automate and control design flo...
Dec. 9, 2016 06:00 AM EST Reads: 818
The WebRTC Summit New York, to be held June 6-8, 2017, at the Javits Center in New York City, NY, announces that its Call for Papers is now open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 20th International Cloud Expo and @ThingsExpo. WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web co...
Dec. 9, 2016 04:15 AM EST Reads: 1,450
Amazon has gradually rolled out parts of its IoT offerings, but these are just the tip of the iceberg. In addition to optimizing their backend AWS offerings, Amazon is laying the ground work to be a major force in IoT - especially in the connected home and office. In his session at @ThingsExpo, Chris Kocher, founder and managing director of Grey Heron, explained how Amazon is extending its reach to become a major force in IoT by building on its dominant cloud IoT platform, its Dash Button strat...
Dec. 9, 2016 04:00 AM EST Reads: 6,342
Complete Internet of Things (IoT) embedded device security is not just about the device but involves the entire product’s identity, data and control integrity, and services traversing the cloud. A device can no longer be looked at as an island; it is a part of a system. In fact, given the cross-domain interactions enabled by IoT it could be a part of many systems. Also, depending on where the device is deployed, for example, in the office building versus a factory floor or oil field, security ha...
Dec. 9, 2016 03:00 AM EST Reads: 395
In addition to all the benefits, IoT is also bringing new kind of customer experience challenges - cars that unlock themselves, thermostats turning houses into saunas and baby video monitors broadcasting over the internet. This list can only increase because while IoT services should be intuitive and simple to use, the delivery ecosystem is a myriad of potential problems as IoT explodes complexity. So finding a performance issue is like finding the proverbial needle in the haystack.
Dec. 9, 2016 02:15 AM EST Reads: 6,234
The idea of comparing data in motion (at the sensor level) to data at rest (in a Big Data server warehouse) with predictive analytics in the cloud is very appealing to the industrial IoT sector. The problem Big Data vendors have, however, is access to that data in motion at the sensor location. In his session at @ThingsExpo, Scott Allen, CMO of FreeWave, discussed how as IoT is increasingly adopted by industrial markets, there is going to be an increased demand for sensor data from the outermos...
Dec. 9, 2016 02:00 AM EST Reads: 3,059
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at 20th Cloud Expo, Ed Featherston, director/senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
Dec. 9, 2016 01:15 AM EST Reads: 1,665
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, discussed how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team at D...
Dec. 9, 2016 12:45 AM EST Reads: 1,214
SYS-CON Events has announced today that Roger Strukhoff has been named conference chair of Cloud Expo and @ThingsExpo 2017 New York. The 20th Cloud Expo and 7th @ThingsExpo will take place on June 6-8, 2017, at the Javits Center in New York City, NY. "The Internet of Things brings trillions of dollars of opportunity to developers and enterprise IT, no matter how you measure it," stated Roger Strukhoff. "More importantly, it leverages the power of devices and the Internet to enable us all to im...
Dec. 9, 2016 12:30 AM EST Reads: 896
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...
Dec. 9, 2016 12:00 AM EST Reads: 719
"Once customers get a year into their IoT deployments, they start to realize that they may have been shortsighted in the ways they built out their deployment and the key thing I see a lot of people looking at is - how can I take equipment data, pull it back in an IoT solution and show it in a dashboard," stated Dave McCarthy, Director of Products at Bsquare Corporation, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 8, 2016 09:45 PM EST Reads: 1,249
What happens when the different parts of a vehicle become smarter than the vehicle itself? As we move toward the era of smart everything, hundreds of entities in a vehicle that communicate with each other, the vehicle and external systems create a need for identity orchestration so that all entities work as a conglomerate. Much like an orchestra without a conductor, without the ability to secure, control, and connect the link between a vehicle’s head unit, devices, and systems and to manage the ...
Dec. 8, 2016 09:15 PM EST Reads: 975
Everyone knows that truly innovative companies learn as they go along, pushing boundaries in response to market changes and demands. What's more of a mystery is how to balance innovation on a fresh platform built from scratch with the legacy tech stack, product suite and customers that continue to serve as the business' foundation. In his General Session at 19th Cloud Expo, Michael Chambliss, Head of Engineering at ReadyTalk, discussed why and how ReadyTalk diverted from healthy revenue and mor...
Dec. 8, 2016 05:45 PM EST Reads: 1,735
As data explodes in quantity, importance and from new sources, the need for managing and protecting data residing across physical, virtual, and cloud environments grow with it. Managing data includes protecting it, indexing and classifying it for true, long-term management, compliance and E-Discovery. Commvault can ensure this with a single pane of glass solution – whether in a private cloud, a Service Provider delivered public cloud or a hybrid cloud environment – across the heterogeneous enter...
Dec. 8, 2016 05:00 PM EST Reads: 1,827
Financial Technology has become a topic of intense interest throughout the cloud developer and enterprise IT communities. Accordingly, attendees at the upcoming 20th Cloud Expo at the Javits Center in New York, June 6-8, 2017, will find fresh new content in a new track called FinTech.
Dec. 8, 2016 04:45 PM EST Reads: 2,262
You have great SaaS business app ideas. You want to turn your idea quickly into a functional and engaging proof of concept. You need to be able to modify it to meet customers' needs, and you need to deliver a complete and secure SaaS application. How could you achieve all the above and yet avoid unforeseen IT requirements that add unnecessary cost and complexity? You also want your app to be responsive in any device at any time. In his session at 19th Cloud Expo, Mark Allen, General Manager of...
Dec. 8, 2016 04:45 PM EST Reads: 1,861
The 20th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held June 6-8, 2017, at the Javits Center in New York City, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Containers, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit your speaking proposal ...
Dec. 8, 2016 04:15 PM EST Reads: 2,326
Bert Loomis was a visionary. This general session will highlight how Bert Loomis and people like him inspire us to build great things with small inventions. In their general session at 19th Cloud Expo, Harold Hannon, Architect at IBM Bluemix, and Michael O'Neill, Strategic Business Development at Nvidia, discussed the accelerating pace of AI development and how IBM Cloud and NVIDIA are partnering to bring AI capabilities to "every day," on-demand. They also reviewed two "free infrastructure" pr...
Dec. 8, 2016 03:30 PM EST Reads: 1,258
Unsecured IoT devices were used to launch crippling DDOS attacks in October 2016, targeting services such as Twitter, Spotify, and GitHub. Subsequent testimony to Congress about potential attacks on office buildings, schools, and hospitals raised the possibility for the IoT to harm and even kill people. What should be done? Does the government need to intervene? This panel at @ThingExpo New York brings together leading IoT and security experts to discuss this very serious topic.
Dec. 8, 2016 03:00 PM EST Reads: 540
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smar...
Dec. 8, 2016 02:30 PM EST Reads: 962