A year ago, software-defined networking (SDN) was nearly synonymous with OpenFlow. But these days, companies like Cisco, Nicira and now VMware, are preaching the word that SDN is about network programmability, not necessarily OpenFlow.
Why the sudden shift? First let's look at what each of these companies is saying.
This month, Cisco unveiled its long-awaited SDN strategy, the Cisco Open Networking Environment (Cisco ONE), which calls for network programmability from the transport layer all the way up to the network services layers (Layers 4-7). To do this, Cisco is not preaching use of OpenFlow or even abstraction and centralization of the control and forwarding planes which might be done in an OpenFlow environment. While Cisco will enable OpenFlow for some users, the company is mostly aiming to usenetwork overlays, like LISP and VXLAN, to bridge the physical and virtual worlds. Furthermore, it will introduce a software development kit (SDK) that makes all of its routers and switches programmable through a universal API, but forwarding decisions will still be distributed throughout the network.
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Meanwhile, VMware networking CTO Allwyn Sequeira told SearchNetworking this month that the company envisions a “software-defined data center.” This might one day rely on OpenFlow, but in the meantime will do just fine using virtual abstractions of firewalls and load balancers, along with VXLAN overlays rather than OpenFlow agents for network slicing and control.
Last month Nicira co-founder Martin Casado explained to SearchNetworking how the company will pull off network virtualization with controllers that talk to edge devices using the OpenFlow protocol. However, Casado stressed that in this scenario, OpenFlow could be replaced by another protocol without customers ever knowing the difference. In other words, the secret in Nicira's sauce is about the network edge overlay model.
Is all this to say that OpenFlow doesn't matter? I don't think so. For one thing, all of these companies are actively involved in the development of OpenFlow through the Open Networking Research Center and the Open Networking Foundation, which means they all find the protocol important.
Each of these companies wants to promote and maintain its own approach to software-defined networking or network virtualization in order to differentiate or gain market control. Cisco has made its bread and butter off of customized ASICs hardware. A true OpenFlow environment with a centralized control plane could rely on x86 hardware and specialized software. Likewise, VMware is a creator of VXLAN and therefore protecting its own technology model by choosing to go with overlays for network virtualization and SDN. Nicira, which does use OpenFlow as one element of its model, aims to be the VMware of networks. It will emphasize its use of edge overlays instead of the involvement of an open source protocol accessible to anyone.
The long and short of this is that there's still a long way to go in OpenFlow development. All of these companies have continued to contribute to that growth while aiming to sell their idea of SDN to the public. It will be up to users to decide whether to wait out OpenFlow development or buy into one vendor's vision of what SDN or network virtualization will look like.