Software-defined networking (SDN) will redefine networking as we know it in the decade to come. At the very core of the SDN architecture, the network control plane is separated from the network forwarding plane. In essence, the network of the future follows the path internal network device design has taken for the last two decades. Here, high intelligence directs fast forwarding.
Does this mean that as the SDN model takes hold and SDN solutions solidify, devices deployed in the network -- switches, routers, access points, etc. -- are relegated to fast forwarding duties only and, therefore, grow to be less intelligent and far less costly over time. The answer is simple. No!
On the contrary, the network device in the SDN environment grows more intelligent — not less. Why? I see five main reasons for this:
The SDN network device needs to take and execute orders on the fly.
With a central command and control system operating at the core of an SDN environment, orders will come fast and furiously. Triggered by any number of events or directives — e.g., changing network conditions, policy enforcement, service activation, electronic threats... -- new orders will be passed along to individual or groups of network devices in bunches... at any time. The expectation is for these devices to execute these orders immediately upon receipt. Understanding that the device is already hard at work directing traffic across the network according to the last set of orders, incorporating new orders received will be a delicate and challenging task — a task requiring much intelligent processing, decision-making, and ultimately, execution. After all, the network can not stop and start all over again.
The SDN network device needs to provide constant yet controlled feedback to the central controller.
The central command and control system within an SDN environment is dependent on a timely stream of accurate and relevant information relating to the operating condition of the network. Network devices are the primary source of this information. They form the eyes and ears of the central command and control system. Without these network devices providing this information, the central command and control system is operating in the dark. It makes sense that the more information, the better the decision — and resulting orders — of the central command and control system. However, as we all know, more information is not always better. Here, network devices will likely need to make intelligent decisions with regards to what should and should not be provided to the central command and control system. Without some intelligent filtering, information overload could easily swamp the central command and control system. Here, the term swamp translates to slowdowns or even failures. This would be catastrophic in an SDN environment.
The SDN network device needs to be easily and highly programmable.
Improved network dynamics is one of the core reasons behind the transition to SDN. While today's networks are able to adapt to changing network conditions to some degree (e.g., link redirects, hardware failovers, policy changes), true network autonomics are still more dream than reality. While SDN will be no "hands-off" panacea with respect to network self-management, it will allow our networks to be more self-aware and self-directed. The network device in this environment needs to be able to "change its spots" on-demand. Today, changing how a network device operates most often requires, at a minimum, staff intervention and, in a worst case scenario, device upgrades. Imagine a device that can take on new responsibilities or even completely different roles at the click of an icon or even in reaction to a new order from the central command and control system. This type of programmability requires not only very sophisticated software, but also well thought out hardware designs. The generic hardwired processor, adapter, or device will not survive in this ever-shifting brave new network world.
The SDN network device needs to match service needs to traffic conditions.
Within an SDN, the network device, while provided continual direction from the central command and control system, is responsible for controlling and moving traffic efficiently and effectively across the network in real-time. The network device is the policeman directing traffic at a busy intersection during rush hour. While orders from the city planner or the police captain may provide overall direction to the traffic control officer, critical decisions still need to be made by the officer on the fly as conditions change — for the better or worse. So too must the network device merge policy and execution as needed. While lines of communications with the central command and control system should always be open, decisions that must be made immediately — in micro or nano seconds — will need to be made by the network device itself. While the SDN model separates the control plane from the forwarding plane, there are still control decisions to be made at the level of the forwarding plane. For example, a large spike in traffic requires some fine-tuning of the traffic queues to maintain service levels for certain flows (e.g., video or voice). This fine-tuning may go against central orders, but it provides the best possible service at the moment the spike hits. The performance requirements of tomorrow's networked users and applications will demand empowered network devices — devices that will be required to make intelligent decisions... at light speed!
The SDN network device needs to be simple to deploy, operate, and enhance.
I am reminded of Leonardo DaVinci's famous statement, "Simplicity is the ultimate sophistication." In networking, complexity is the enemy. And simple does not equate to dumb. On the contrary, the simple network device does more, while demanding less. It requires less time. It requires less staff. It requires less reinvestment. It drives less risk. Think how much more you would like to do with QoS in your network. Think how many versions of IOS are active in your network. Think how difficult it was to accommodate that last business application dropped on your network. In networking, it seems that nothing is ever simple. Why is that? Because simple is hard. As DaVinci indicated, simple is sophisticated. The simple network device operating within an SDN environment will be both simple and sophisticated. It will certainly not be dumb!
If you look at SDN as a way to "dumb down" your network and lower your cost of networking through generic device purchases, you are not interpreting the future benefits of SDN properly. The low-cost generic network device will not succeed in the SDN environment. Rather, the network device grows to be even more capable, more responsible, and more decisive in the SDN future. If you, instead, look at SDN as a way to simplify your network, better utilize networking and networked resources, and, last but certainly not least, improve network dynamics and therefore network service levels, then you are more on track to our SDN future — and more in line with future network device design.