For someone trying to understand SDN, it can be difficult to develop a holistic view from vendor perspectives designed to “sell” specific solutions. A holistic view is worth having, though, as a variety of SDN technologies underpin new styles of dynamic IT. In other words, SDN technologies are essentially the palette by which networks are created to better support a variety of use cases like cloud, NFV, analytics, application container platforms (e.g. Docker), and DevOps frameworks.
And just like an artist’s palette, it’s often the combination of elements (in this analogy, technologies) that enables a novel result. For SDN, these technologies span multiple vendors, organizations and communities.
With the above in mind, I’ve pulled together an independent perspective designed to capture and explain the broad set of SDN technologies that has been introduced to date.
A detailed view is presented in this freely available white paper. The remainder of this post is dedicated to an outline of that paper, including key findings and highlights.
SDN – Don’t Sweat the Definition
There is (still) no precise definition of SDN. There probably never will be. That’s okay. Trying to create a precise definition for what has also become a marketing term is a fool’s errand.
Still, there is a general sense in the market of desirable trends and characteristics for network architectures. Trends toward software elements and control, programmability of the network (for automation or higher-order systems), and open interfaces and standards are technical themes for what many would consider to be SDN. Even here, there is room for interpretation, but these are reasonable “boundaries” by which to discuss SDN technologies.
Making Sense of the Mix
Many technologies still fit into the claimed SDN boundary, so categorizing them would be helpful. In this case, there is no such thing as a correct categorization model, but it’s useful to group them by architectural approach.
Figure 1 – SDN Technology Categories
These categories are:
- OpenFlow, which, despite some claims to the contrary, is certainly not dead (or even fading), as evidenced by its use in some modern DC fabrics, and ongoing work to up-level abstractions and programming model.
- Network Control Plane Extensions (e.g. PCE, BGP-LS) that allow some degree of network visibility and/or control to external software elements (for multilayer networks as just one example).
- Overlay Abstraction, where new network abstractions (e.g. DC fabrics) are created on top of existing networks. This category launched the latest round of network virtualization discussion (but isn’t the only way to implement it).
Some Cross-Cutting Implications
While various SDN technologies gained traction by targeting specific use cases, SDN approaches in general have also led to exciting capabilities such as highly granular security models (e.g. microsegmentation).
The latest hot topic in SDN is around policy, with its implications for how the advanced capabilities provided by SDN will be consumed (both by operators, and programmatically by higher-order systems).
This perspective is based on five years of interest and experience with the SDN topic. That experience includes interactions with smart people and organizations that embraced the disruption, saw it as a threat, or viewed it as both.
Again, this post is just a brief summary of the information and analysis contained in the white paper. I hope you also take the opportunity to read the paper, and I look forward to your comments and feedback on this fascinating and evolving topic.
It’s an exciting time in networking.
Check out the freely available white paper, Understanding SDN: A Survey of SDN Technologies and Associated Use Cases to become familiar with the myriad of approaches being called SDN and to understand why they are important