Ronny Lam


The Case for SDN

Bob Emmerson is trying to make the case for Software Defined Networking:

Using the command line interface (CLI) to program the individual switches is something that Cisco and Cisco-trained IT staff had to do in order to meet customer requests for policy changes. However, this is an expensive, time-consuming task and SDN can provide a model that automates networking provisioning. Therefore, IT departments won’t need to jump through such high-tech hoops in future: instead untrained staff can employ the model to develop self-service clouds. SDN also removes router/switch lock-in: switches and routers are now abstracted, which allows enterprises to swap between vendors.

I fully agree with the above challenges we have to solve in todays growing networks. But I doubt SDN is going to solve that. SDN is only going to provide the programmatic interface to the centralized controller. It is the north-bound interface of this SDN controller that is on the basis of a full solution:

This need is obvious, but how is this task realized? HP’s model is built on top of the company’s Virtual Application Network SDN controller. The APIs used to communicate between the layers of the SDN stack are grouped based on their function in the architecture: Northbound OpenStack APIs communicate between controllers and applications, and southbound OpenFlow APIs communicate between controller and infrastructure. Automation of the network configuration process is based on the policy-driven decisions built into the network applications.

So the answer is in the applications on top of SDN? I think so, but if we look at Bob’s picture I would think that we can take this one step further. The goal in my opinion is not SDN, but is to provide Network Automation capabilities. If we cut out the middle SDN layer and program the network directly from the application layer, than we don’t need to buy new hardware, but we can still have automation capabilities in the application layer. That does not make the SDN case useless. In fact, the use of SDN, allows for more applications to program the network, instead of only one.


Full disclosure: at NetYCE we already have an application that allows you to program the network based on existing hardware, without the need for an SDN layer in between.