In my blog yesterday I talked about the risks to SDN, with the largest being a disconnect between SDN missions and SDN implementations. I got a couple of emails asking just what “SDN missions” might be, and I think that’s a fair question. Missions reflect a benefit case, after all, and benefit cases are needed to drive SDN deployment. I’ve been working through a market model of SDN, and while the full set of results won’t be available till next month, I do have some “mission” comments I can make now.
Whatever one of the three “models” of SDN architecture you accept (central/OpenFlow, distributed/IP, or Nicira-like) the fact is that all of the models have limitations in terms of mission. There is absolutely no reason to believe that complete central control of a service network at even the scale of a large enterprise could be made to work. The notion that SDN might be less costly (operationally or in capex) than current networks can be defended in limited geographies like a data center, and can be postulated with reasonable confidence at the metro level, but it can’t be defended globally or even nationally based on what we have. If you try to make an SDN value proposition you can make it inside a data center or perhaps in an IP core area (as Google has proved). For anything broader you’ll have to wait a bit.
This is the core of the mission challenge. It’s easy to propose to pack the family into the car and head out to Disneyworld, then get everyone to focus on the packing and route planning. If you didn’t know where you were taking them things might be a bit more challenging. We really need to have an SDN end-game to justify getting enterprise or operator planners involved in laying out their SDN direction. Who is articulating that compelling destination? Vendors like Cisco may offer an architecture for SDN but what are the specific driving benefits, the utopian future vision?
Devices would be helpful to gaining a sense of SDN evolution. If you want to do more than experiment with SDN today or deploy it in a data center, you have to do so by adding SDN/OpenFlow features to current hardware. Well, that pretty well eradicates the cost advantage doesn’t it? I buy what I always did, I add a layer of SDN to it, and somehow that becomes cheaper? How about benefits beyond device cost? The original goal of SDN (before we SDN-washed everything we could get our hands on) was to centralize network control so as to improve utilization and operations efficiency. Can that be done? We don’t really have a complete picture to measure the prospective outcome. And few vendors have articulated a complete vision of even a limited SDN mission. None have articulated a complete vision of a universal SDN mission. If SDN isn’t universal in scope, can it have profound operations benefits?
There are clear SDN values, real missions. You can utilize SDN to improve traffic management in data centers and core networks to enhance availability. You can utilize SDN to combine provisioned services with best-efforts infrastructure if you’re an operator. You can tie SDN easily to tenants in a public cloud and to applications in a private cloud. We could build a whole new vision of security based on SDN, a new model for cloud service infrastructure. So where are the models for these things? You tell me. Only a couple vendors have met even a basic test of functionality in their briefings to me on SDN. Most tell me that other pieces are from other vendors. In the end, nearly all vendors tell us that they are supporting the cloud revolution with their SDN plan, but if you define anything that connects software as SDN you’ve set a pretty low bar for yourself in supporting revolutions.
So am I becoming an SDN skeptic? No, I’m becoming hype-shy having been bitten multiple times. I think, based on what I’ve gotten from buyers and vendors, I could draw out an “SDN destination plan” for the missions I outlined above. I think others could do the same thing, but I don’t think we’re demanding that anyone do that. We are so quick to declare SDN utility and interest because SDN is “new” and “revolutionary” that we aren’t insisting vendors offer more in SDN than simple entertainment. Maybe that Disneyworld analogy was better than I thought. SDN Fantasyland, anyone?
