|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-Things discussions can end up either going down the consumer gadget rabbit hole or focused on the sort of data logging that industrial manufacturers have been doing forever. However, in fact, companies today are already using IoT data both to optimize their operational technology and to improve the experience of customer interactions in novel ways. In his session at @ThingsExpo, Gordon Haff, Red Hat Technology Evangelist, will share examples from a wide range of industries – includin...
Dec. 5, 2016 04:15 AM EST Reads: 1,607
Unless your company can spend a lot of money on new technology, re-engineering your environment and hiring a comprehensive cybersecurity team, you will most likely move to the cloud or seek external service partnerships. In his session at 18th Cloud Expo, Darren Guccione, CEO of Keeper Security, revealed what you need to know when it comes to encryption in the cloud.
Dec. 5, 2016 04:00 AM EST Reads: 4,670
We're entering the post-smartphone era, where wearable gadgets from watches and fitness bands to glasses and health aids will power the next technological revolution. With mass adoption of wearable devices comes a new data ecosystem that must be protected. Wearables open new pathways that facilitate the tracking, sharing and storing of consumers’ personal health, location and daily activity data. Consumers have some idea of the data these devices capture, but most don’t realize how revealing and...
Dec. 5, 2016 04:00 AM EST Reads: 5,076
"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.
Dec. 5, 2016 03:30 AM EST Reads: 933
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. 5, 2016 01:30 AM EST Reads: 743
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. 5, 2016 12:45 AM EST Reads: 1,569
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. 5, 2016 12:30 AM EST Reads: 6,083
According to Forrester Research, every business will become either a digital predator or digital prey by 2020. To avoid demise, organizations must rapidly create new sources of value in their end-to-end customer experiences. True digital predators also must break down information and process silos and extend digital transformation initiatives to empower employees with the digital resources needed to win, serve, and retain customers.
Dec. 5, 2016 12:15 AM EST Reads: 1,159
"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. 4, 2016 10:45 PM EST Reads: 1,000
Fact is, enterprises have significant legacy voice infrastructure that’s costly to replace with pure IP solutions. How can we bring this analog infrastructure into our shiny new cloud applications? There are proven methods to bind both legacy voice applications and traditional PSTN audio into cloud-based applications and services at a carrier scale. Some of the most successful implementations leverage WebRTC, WebSockets, SIP and other open source technologies. In his session at @ThingsExpo, Da...
Dec. 4, 2016 10:45 PM EST Reads: 1,672
Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more business becomes digital the more stakeholders are interested in this data including how it relates to business. Some of these people have never used a monitoring tool before. They have a question on their mind like “How is my application doing” but no id...
Dec. 4, 2016 06:30 PM EST Reads: 2,177
@GonzalezCarmen has been ranked the Number One Influencer and @ThingsExpo has been named the Number One Brand in the “M2M 2016: Top 100 Influencers and Brands” by Onalytica. Onalytica analyzed tweets over the last 6 months mentioning the keywords M2M OR “Machine to Machine.” They then identified the top 100 most influential brands and individuals leading the discussion on Twitter.
Dec. 4, 2016 06:30 PM EST Reads: 2,035
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. 4, 2016 06:00 PM EST Reads: 1,545
"IoT is going to be a huge industry with a lot of value for end users, for industries, for consumers, for manufacturers. How can we use cloud to effectively manage IoT applications," stated Ian Khan, Innovation & Marketing Manager at Solgeniakhela, in this SYS-CON.tv interview at @ThingsExpo, held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 4, 2016 04:15 PM EST Reads: 4,210
"We're a cybersecurity firm that specializes in engineering security solutions both at the software and hardware level. Security cannot be an after-the-fact afterthought, which is what it's become," stated Richard Blech, Chief Executive Officer at Secure Channels, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 4, 2016 04:15 PM EST Reads: 626
Information technology is an industry that has always experienced change, and the dramatic change sweeping across the industry today could not be truthfully described as the first time we've seen such widespread change impacting customer investments. However, the rate of the change, and the potential outcomes from today's digital transformation has the distinct potential to separate the industry into two camps: Organizations that see the change coming, embrace it, and successful leverage it; and...
Dec. 4, 2016 03:00 PM EST Reads: 3,262
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, discussed the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
Dec. 4, 2016 02:15 PM EST Reads: 2,015
Internet of @ThingsExpo, taking place June 6-8, 2017 at the Javits Center in New York City, New York, is co-located with the 20th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. @ThingsExpo New York Call for Papers is now open.
Dec. 4, 2016 02:00 PM EST Reads: 1,911
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. 4, 2016 02:00 PM EST Reads: 616
We are always online. We access our data, our finances, work, and various services on the Internet. But we live in a congested world of information in which the roads were built two decades ago. The quest for better, faster Internet routing has been around for a decade, but nobody solved this problem. We’ve seen band-aid approaches like CDNs that attack a niche's slice of static content part of the Internet, but that’s it. It does not address the dynamic services-based Internet of today. It does...
Dec. 4, 2016 02:00 PM EST Reads: 945