It feels like that even OpenFlow could play a role in SDN (as also OpenDaylight seems to support it) when either more custom ASICs (likely) or more scalable commodity ASICs show up (rather unlikely) and the control plane becomes much more scalable. I think the ONF did a good job of starting the discussions around SDN but as a highlighted in various blogs the focus has shifted from a protocol discussion on the southbound API side to a much broader architectural discussion around what you can really do with SDN leveraging Northbound APIs from various solutions (due to the lack of standardization) and what the benefits are.

So really the key elements and benefits of an SDN solution are in the focus now - and the experience from last weeks Interop confirms this. Not only were the keynotes on Wednesday not focused specifically on OpenFlow but also one of the hot products of this year's show identified by Network World is a SDN solution that does not use OpenFlow - as a lot of SDN startups do not use it either, see a former blog on SDxCentral from Isabelle Guis about this.

From my perspective the attributes that make up an SDN architecture are

• A centralized point of management & control that can easily monitor resources and enforce policies for the whole network, including Data Center servers, applications, users and devices – so that high quality user experience can be achieved, with simplified operations and compelling OpEx savings
• A programmable environment that offers flexibility through automation and orchestration across the entire network fabric – so that the entire network (from data center to the edge) can be easily and dynamically be provisioned to improve network efficiencies and reduce costs
• Open application integration and an API infrastructure that enables rapid integration of any application from any vendor from the virtualized data center to the mobile edge

So what's next? OpenDaylight as a open source project that provides a controller platform which is open to various southbound APIs is an interesting move within the industry - yet to see the outcome of this and how it evolves over time. It supports the OSGi framework and bidirectional REST for the northbound API . The business logic and algorithms reside in the applications that are integrated via the Northbound API. These applications leverage the controller to gather network intelligence as well as to orchestrate network configuration after appropriate network data computation.

Will OpenDaylight be THE northbound API - or will be there many or at least a few? Which will be the ones? Lets see how the market evolves but for sure it will take a few years before anyone can give a solid answer to this question. Additional insight and links are included in a blog by Jordan at GigaOM.