The Case Against SDN

Andrew Froehlich, Network Engineer & IT Consultant | 2/11/2013 | 5 comments

Andrew Froehlich
Software-defined networks (SDNs) might be a tough sell to both network engineers and CIOs who must choose whether to implement them.

Most IT professionals who gravitate toward a career in networking do so because they like the simplicity of how networks operate. Hardware components, software, and protocols are highly robust, and the network either works or doesn't. There's very little in between. And there's a reason simplicity is built into networking components. If the network is flaky, so is everything riding on top of it.

The SDN concept seems great on paper. It removes intelligence from networking hardware and centralizes it, so it can be managed in a single location. Traffic routing decisions are made at the management plane level and then pushed out to the unintelligent data plane hardware, where routing and switching decisions are executed. This form of intelligence decoupling has already been applied to controller-based wireless infrastructures that leverage dumb access points managed by a centralized server. SDNs build on that concept and take it to the next level.

The primary benefit SDN advocates like to hype is that centralizing traffic routing decisions offers a complete view of the network from end to end. Because of this, reconfigurations can be managed and pushed out networkwide at once, as opposed to making changes one device at a time along the path where traffic flow changes need to be made.

This is all wonderful, but in most enterprise networks, major data flow reconfigurations are few and far between. The need for so much flexibility and control from one end of the network to the other seems unnecessary for most organizations. In fact, many would agree that a great network design is one where very few changes will be required through the life of the hardware.

SDNs go against the "keep it simple, stupid" mantra by which network engineers live and die. Implementing one could destabilize your network for the sake of flexibility -- a benefit that's not widely needed.

I do admit there are some areas where SDNs would be a great success today. Internet and cloud service providers need the type of flexibility that SDNs offer. Because they have customers who are constantly adding, removing, and shifting applications and data, they need the ease of end-to-end management and configuration. Also, as your datacenter becomes more and more virtualized, I can see the use for central control of its network and storage components. But an end-to-end SDN in an enterprise environment? It's simply not needed.

View Comments: Newest First | Oldest First | Threaded View
JohnVerity   The Case Against SDN   5/30/2013 8:32:36 PM
Re: Big Enough to Fail?
SDNs go against the "keep it simple, stupid" mantra by which network engineers live and die.

I disagree. I don;t think there's anything less simple than networks, especially when it comes to reconfiguring them. Someone has compared this task to one of those puzzles we used to play with, with a grid of 16 squares in which 15 tiles could be slid up and down and left and right. Inevitably, moving one tile disrupted the pattern of many others, and trying to fix them created more disruptions. 

The great thing about SDN is that it will rely on a very detailed and maleable model of the network and provide a central control point that will make for much greater and faster flexibility along with much greater security. For once, it will be quite clear what is attached to what.
dilzwilz   The Case Against SDN   2/20/2013 12:38:40 PM
Case Against SDN
I like your point regarding good network design; how good design, in essence thwarts the need to redesign in order to accomodate future network traffic. Don't get me wrong, for I love the idea of "if it aint broke, you're not looking hard enough", and re-engineering, But I also tend to think that ideas like SDN are born out of 1. not understanding a [in this case, Networking] technology, design, protocols, and everything else associated with it ..and therefore 2. trivializing the importance of not modifying the infrastructure everytime there's some project or development. Rather,  the network guru can answer the project's needs by creating a VLAN [for instance], or something. 3. the resentment of having to deal with the guru "everytime we want to do something". "Can't somebody come up with a new way to do networking? Can't the software guys make up a way to change the network?"
Andrew Froehlich   The Case Against SDN   2/12/2013 9:42:52 PM
Re: Big Enough to Fail?
SDNs are less reliable for two reasons. First, the technology is still untested. There's likely bugs that will need to be worked out. Second, there won't be many network professionals that are well versed in SDN management. Both can and will be overcome...but it will take time.
User Ranking: Blogger
David Wagner   The Case Against SDN   2/11/2013 11:58:54 AM
Re: Big Enough to Fail?
Also, Andrew. I remember when a similar argument was made about server virtualization. Only big enterprises needed it was the mantra, but clearly that wasn't the case. Is this just a short term issue and we're all going to be using SDN soon?
David Wagner   The Case Against SDN   2/11/2013 11:57:57 AM
Big Enough to Fail?
Interestingly enough, it seems like you are saying that really big networks need SDN, but that SDN is less reliable. Is it safe ot say then that the bigger th network the less reliable it is anyway and SDN will help with that problem? But that smaller networks don't need it?

The blogs and comments posted on do not reflect the views of TechWeb,, or its sponsors., TechWeb, and its sponsors do not assume responsibility for any comments, claims, or opinions made by authors and bloggers. They are no substitute for your own research and should not be relied upon for trading or any other purpose.

More Blogs from Andrew Froehlich
Andrew Froehlich   5/6/2014   13 comments
Not all clouds are equal. That's a pretty obvious statement that we can all agree on. Cloud service providers offer differing levels of services, redundancy, and customer service -- all at ...
Andrew Froehlich   4/30/2014   10 comments
In order for enterprise employees to work together as one unified group, they must follow carefully written policies and procedures -- but every once in a while, you may find yourself in ...
Andrew Froehlich   4/22/2014   49 comments
For those of us who study enterprise IT security, last year's Target store hack turned out to be a fantastic case study that was loaded with lessons to learn.
Andrew Froehlich   4/16/2014   22 comments
With news that Google slashed the price of their big-data offering "Big Query" by up to 85 percent, one has to wonder if the move is to ward off competitors -- or simply that the ...
Andrew Froehlich   3/18/2014   27 comments
At a recent South By Southwest Interactive conference in Austin, Edward Snowden said the NSA is "setting fire to the future of the Internet." In light of this, the World Wide Web ...
Latest Archived Broadcast
We talk with Bernard Golden about accelerating application delivery in the cloud.
On-demand Video with Chat
Register for this video discussion to learn how tablets can provide true business usability and productivity.
E2 IT Migration Zones
IT Migration Zone - UK
Why PowerShell Is Important
Reduce the Windows 8 Footprint for VDI
Rethinking Storage Management
IT Migration Zone - FR
SQL Server : 240 To de mémoire flash pour votre data warehouse
Quand Office vient booster les revenus Cloud et Android de Microsoft
Windows Phone : Nokia veut davantage d'applications (et les utilisateurs aussi)
IT Migration Zone - DE
Cloud Computing: Warum Unternehmen trotz NSA auf die „private“ Wolke setzen sollten
Cloud Computing bleibt Wachstumsmarkt – Windows Azure ist Vorreiter
Like Us on Facebook
Twitter Feed
Enterprise Efficiency Twitter Feed
Site Moderators Wanted
Enterprise Efficiency is looking for engaged readers to moderate the message boards on this site. Engage in high-IQ conversations with IT industry leaders; earn kudos and perks. Interested? E-mail:
Dell's Efficiency Modeling Tool
The major problem facing the CIO is how to measure the effectiveness of the IT department. Learn how Dell’s Efficiency Modeling Tool gives the CIO two clear, powerful numbers: Efficiency Quotient and Impact Quotient. These numbers can be transforma¬tive not only to the department, but to the entire enterprise.

Read the full report
The State of Enterprise Efficiency in the Virtual Era: Virtualization – Smart Approaches to Maximize Gains
Virtualization is a presence in nearly all enterprise data centers. But not all companies are using it to its best effect. Learn the common characteristics of success, what barriers companies face, and how to get the most from your efforts.

Read the full report
Informed CIO: Dollars & Sense: Virtual Desktop Infrastructure
Cut through the VDI hype and get the full picture -- including ROI and the impact on your Data Center -- to make an informed decision about your virtual desktop infrastructure deployments.

Read the full report
A Video Case Study – Translational Genomics Research Institute
e2 Video

On the Case
TGen IT: Where We're Going Next

7|11|12   |   08:12   |   10 comments

Now that TGen has broken new ground in genomic research by using Dell's storage, cloud, and high-performance computing solutions, the company discusses what will come next for it and for personalized medicine.
On the Case
Better Care Through Better Communications

6|6|12   |   02:24   |   11 comments

The achievements of the TGen/Dell project could improve how all people receive healthcare, because they are creating ways to improve end-to-end communication of medical data.
On the Case
TGen IT: Where We Are Now

5|15|12   |   06:58   |   6 comments

TGen is breaking new ground in genomic research by using Dell's storage, cloud, and high-performance computing solutions.
On the Case
TGen IT: Where We Were

4|27|12   |   06:45   |   10 comments

The Translational Genomics Research Institute wanted to save lives, but its efforts were hobbled by immense computing challenges related to collecting, processing, sharing, and storing enormous amounts of data.
On the Case
1,200% Faster

4|18|12   |   02:27   |   12 comments

Through their partnership, Dell and TGen have increased the speed of TGen’s medical research by 1,200 percent.
On the Case
IT May Improve Children's Chances of Survival

4|17|12   |   02:12   |   8 comments

IT is helping medical researchers reach breakthroughs in a way and pace never seen before.
On the Case
Medical Advances in the Cloud

4|10|12   |   1:25   |   5 comments

TGen and Dell are pushing the boundaries of computing, and harnessing the power of the cloud to improve healthcare.
On the Case
TGen: Living the Mission

4|9|12   |   2:25   |   3 comments

TGen's CIO puts the organizational mission at the heart of everything the IT staff does.
On the Case
TGen Speeding Up Biomedical Research to Save More Lives

4|5|12   |   1:59   |   6 comments

The Translational Genomics Research Institute is revamping its computing to improve speed, storage, and collaboration – and, most importantly, to save lives.
On the Case
Computing Power Helping to Save Children's Lives

3|28|12   |   2:13   |   3 comments

The Translational Genomics Institute’s partnership with Dell is enabling them to treat kids with neuroblastoma more quickly and save more lives.
Tom Nolle
The Big Reason to Use Office

3|18|14   |   02:24   |   46 comments

Office and personal productivity tools come in a first-class and coach flavor set, but what makes the difference is primarily little things that most users won't encounter. What's the big issue in using something other than Office, and can you get around it?
E2 Editors
SPONSORED: Mobile Security — A Use Case

3|4|14   |   04:27   |   16 comments

New mobile security solutions can accommodate a wide array of needs, including those of a complex university environment.
Tom Nolle
Killing Net Neutrality Might Save You Money

1|16|14   |   2:13   |   16 comments

The DC Court of Appeals voided most of the Neutrality Order, and whatever it might mean for the Internet overall, it might mean better and cheaper Internet VPNs for businesses.
Tom Nolle
The Internet of Everythinguseful

1|10|14   |   2:18   |   19 comments

We really don't want an "Internet of Everything" but even building an Internet of Everythinguseful means setting some ground rules to insure there's value in the process and that costs and risks are minimized.
Tom Nolle
Maturing Google Chrome

12|30|13   |   2.18   |   25 comments

Google's Chrome OS has a lot of potential value and a lot of recent press, but it still needs something to make it more than a thin client. It needs cloud integration, it needs extended APIs via web services, and it needs to suck it up and support a hard drive.
Sara Peters
No More Cookie-Cutter IT

12|23|13   |   03.58   |   21 comments

Creating the right combination of technology, people, and processes for your IT organization is a lot like baking Christmas cookies.
Sara Peters
Smart Wigs Not a Smart Idea

12|5|13   |   3:01   |   46 comments

Sony is seeking a patent for wigs that contain computing devices.
Tom Nolle
Cloud in the Wild

12|4|13   |   02:23   |   15 comments

On a recent African trip I saw examples of the value of the cloud in developing nations, for educational and community development programs. We could build on this, but not only in developing economies, because these same programs are often under-supported even in first-world countries.
E2 Editors
SPONSORED: Is Malware Evading Your IPS?

11|18|13   |   03:16   |   4 comments

Intrusion prevention software is supposed to detect and block malware intrusions, but clever malware authors can evade your IPS in these five main ways.
Sara Peters
Where Have All the Mentors Gone?

9|27|13   |   3:15   |   38 comments

A good professional mentor can change your life for the better... but where do you find one?
Tom Nolle
SDN Wars & You Could Win

9|17|13   |   2:10   |   5 comments

VMware's debate with Cisco on SDN might finally create a fusion between an SDN view that's all about software and another that's all about network equipment. That would be good for every enterprise considering the cloud and SDN.
Ivan Schneider
The Future of the Smart Watch

9|12|13   |   3:19   |   39 comments

Wearing a bulky, oversized watch is good training for the next phase in wristwatches: the Internet-enabled, connected watch. Why the smartphone-tethered connected watch makes sense, plus Ivan demos an entirely new concept for the "smart watch."
Tom Nolle
Cutting Your Cloud Storage Costs

9|4|13   |   2:06   |   3 comments

Cloud storage costs are determined primarily by the rate at which files are changed and the possibility of concurrent access/update. If you can structure your storage use to optimize these factors you can cut costs, perhaps to zero.
Sara Peters
Do CIOs Need an IT Background?

8|29|13   |   2:11   |   23 comments

Most of the CIOs interviewed in the How to Become a CIO series did not start their careers as IT professionals. So is an IT background essential?
Ivan Schneider
The Internet Loves Birthdays

8|27|13   |   3:25   |   69 comments

The Internet has evolved into a machine for drumming up a chorus of "Happy Birthday" messages, from family, friends, friends of friends who you added on Facebook, random people that you circled on G+, and increasingly, automated bots. Enough already.