What are the challenges in SDN enabling legacy infrastructure?
If you look at how HP's switches helped the Stanford University network evolve to OpenFlow, they just added them one at a time. We've seen the overlay approach, which is sort of a starter tunnel through the legacy stuff, be attractive to a number of the customer of Nicira, now VMware. I think it's good to get some experience but I don't see that approach -- adding complexity to something that's already complex -- really following the motivations that drove us to develop SDN. Taking a legacy networking device that has a lot of complexity, a lot of control in it, a lot of custom ASICs and proprietary operating systems, and opening the lid, dumping some OpenFlow inside and closing it, and saying it's now SDN. The principles that govern us are simplifying the networking devices, simplifying operation, logically centralizing control so that it applies to multiple switches and doesn't have to replicate them, and having a single place to have a programming interface and something that's robust -- those are the principles that we adhere to. This doesn't seem to follow those same principles because it's adding complexity to complexity. And we're trying to extract simplicity from complexity. If it succeeds in the market, well that's something; but it's not our view of what SDN is for, actually.
Do you view Cisco's onePK as an SDN?
Let me just make an interesting observation here: As far as I understand, onePK defines some interfaces to the routing information base, the RIB. So it's an open interface in that you can program to it from the same company's controller. But I don't think you would have seen an open interface like this had it not been for OpenFlow and the SDN movement. So, what is its use? I think its use is in getting companies and their customers to think in new ways about the networking programmable.
Can you elaborate on the need for an east-west protocol? Is there work underway for a controller-to-controller protocol for federated SDNs?
We don't have any formal effort underway on that yet. If you look at the rate at which telcos roll stuff out, it will be a while before we get to that. We're doing the most important things first. It's certainly a very interesting question, there will be a need for that. The way people are doing it now, they're using BGP to connect these different OpenFlow networks. That will probably be around for a while. We have seen people like Google have hierarchies of OpenFlow controllers -- a number of companies have done this -- where master and slave are more peer relationships. There's a lot of experimentation going on there. And we'll have to find out what problems we can help the industry solve. Long term, I'm not sure BGP could be that protocol. It wasn't made for this. As much that can be leveraged will be leveraged, but I think it's too soon to say. If there is a simple right answer, that's what the industry will adopt.
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