Remember OpenFlow? The hammer that was set to solve all of our vaguely nail-like problems? Remember how everything was going to be based on OpenFlow going forward and the world was going to be a better place? Or how heretics like Ivan Pepelnjak (@IOSHints) that dared to ask questions about scalability or value of application were derided and laughed at? Yeah, good times. Today, I stand here to eulogize OpenFlow, but not to bury it. And perhaps find out that OpenFlow has a much happier life after death.
OpenFlow Is The Viagra Of Networking
OpenFlow is not that much different than Sildenafil, the active ingredient in Vigara. Both were initially developed to do something that they didn’t end up actually solving. In the case of Sildenafil, it was high blood pressure. The “side effect” of raising blood pressure in a specific body part wasn’t even realized until after the trials of the drug. The side effect because the primary focus of the medication that was eventually developed into a billion dollar industry.
In the same way, OpenFlow failed at its stated mission of replacing the forwarding plane programming method of switches. As pointed out by folks like Ivan, it had huge scalability issues. It was a bit clunky when it came to handling flow programming. The race from 1.0 to 1.3 spec finalization left vendors in the dust, but the freeze on 1.3 for the past few years has really hurt innovation. Objectively, the fact that almost no major shipping product uses OpenFlow as a forwarding paradigm should be evidence of it’s failure.
The side effect of OpenFlow is that it proved that networking could be done in software just as easily as it could be done in hardware. Things that we thought we historically needed ASICs and FPGAs to do could be done by a software construct. OpenFlow proved the viability of Software Defined Networking in a way that no one else could. Yet, as people abandoned it for other faster protocols or rewrote their stacks to take advantage of other methods, OpenFlow did still have a great number of uses.
OpenFlow Is a Garlic Press, Not A Hammer
OpenFlow isn’t really designed to solve every problem. It’s not a generic tool that can be used in a variety of situations. It has some very specific use cases that it does excel at doing, though. Think more like a garlic press. It’s a use case tool that is very specific for what it does and does that thing very well.
This video from Networking Field Day 13 is a great example of OpenFlow being used for a specific task. NEC’s flavor of OpenFlow, ProgrammableFlow, is used on conjunction with higher layer services like firewalls and security appliances to mitigate the spread of infections. That’s a huge win for networking professionals. Think about how hard it would be to track down these systems in a network of thousands of devices. Even worse, with the level of virulence of modern malware, it doesn’t take long before the infected system has infected others. It’s not enough to shut down the payload. The infection behavior must be removed as well.
What NEC is showing is the ultimate way to stop this from happening. By interrogating the flows against a security policy, the flow entries can be removed from switches across the network or have deny entries written to prevent communications. Imagine being able to block a specific workstation from talking to anything on the network until it can be cleaned. And have that happen automatically without human interaction. What if a security service could get new malware or virus definitions and install those flow entries on the fly? Malware could be stopped before it became a problem.
This is where OpenFlow will be headed in the future. It’s no longer about adapting the problems to fit the protocol. We can’t keep trying to frame the problem around how much it resembles a nail just so we can use the hammer in our toolbox. Instead, OpenFlow will live on as a point protocol in a larger toolbox that can do a few things really well. That means we’ll use it when we need to and use a different tool when needed that better suits the problem we’re actually trying to solve. That will ensure that the best tool is used for the right job in every case.
OpenFlow is still useful. Look at what Coho Data is using it for. Or NEC. Or any one of a number of companies that are still developing on it. But the fact that these companies have put significant investment and time into the development of the protocol should tell you what the larger industry thinks. They believe that OpenFlow is a dead end that can’t magically solve the problems they have with their systems. So they’ve moved to a different hammer to bang away with. I think that OpenFlow is going to live a very happy life now that people are leaving it to solve the problems it’s good at solving. Maybe one day we’ll look back on the first life of OpenFlow not as a failure, but instead as the end of the beginning of it become what it was always meant to be.
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Nice blog. I agree that the original vision of OpenFlow as a “one protocol to rule them all” concept did not work. There’s too little intersection in all of the crazy things that forward packets (x86 chips for software switches, NPUs and FPGAs, versus every ASIC companies different set of features).
That said, (and agreeing with you in a different way) there is still a lot of utility in thinking of OpenFlow as a TLV-based open remote protocol for managing the forwarding plane. That is, much like a supervisor card manages many line cards, an OpenFlow controller can reduce the number of management consoles needed across a bunch of 1U pizza boxes switches.
Of course, under the covers, all of our products quite successfully use OpenFlow (currently 1.4-ish with some significant extensions) at some pretty significant scale, so this is more than just an academic discussion for me 🙂
Fwiw, I wrote (a while back now) some more nuanced thoughts about the original academic OpenFlow versus the more modern OpenFlow that gets used today in a three-part blog series: feel free to check it out:
Thanks for the blog as always.
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Veryy creative post