Software-defined networking (SDN) was one of the hot new technologies in 2013, as industry experts wanted to talk about its potential to revolutionize data processing. Not only that, but companies were keen to get in on the action that was forecasted by many to mushroom in demand over the next 5 years. The market size in 2018 is predicted to be somewhere between $8 billion and $35 billion depending on which analysts you pay attention to. This Google chart shows that while the level of interest in SDN may have dropped off somewhat over the last year, it still remains an area of interest for many people. Let’s go through some of the fundamentals of SDN and its benefits, along with the ways in which partners are going about implementing it.
From no interest until June 2012, SDN has spiked in interest and remained relevant over the past 2 years (source)
The way in which people use computers has advanced rapidly over the past three decades due to the massive proliferation of mobile connected devices and the sheer number of computing devices that are now in existence. Indeed, last month the number of mobile devices officially surpassed the number of people in the world, and they are multiplying five times faster than we are (which sounds very much like the beginning of the Terminator movies, but I digress). The networks themselves have become a critical component of all infrastructures in society and an important part of the growing public and private clouds. Despite this exponential growth in computers, the way that networking is done has remained virtually unchanged from the 1980s. Traditional networking approaches have become too complex, closed, and proprietary. They have become a barrier to creating new, innovative services within a single data center, on interconnected data centers, or within enterprises, and an even larger barrier to the continued growth of the Internet. Unfortunately it is not just a question of building more data centers to solve this problem, as the ability to absorb the costs of network expansion in the current paradigm is lacking.
The root cause of a network’s limitation is that it is built using switches, routers, and other devices that have become exceedingly complex because they implement an ever-increasing number of distributed protocols and use closed and proprietary interfaces. Each of the many processes of a router or switch are assigned to one of the following planes of operation: Forwarding Plane, Control Plane or Management Plane. This environment of complexity has made it nigh on impossible for network operators, third parties and even vendors to innovate. Operators cannot customize and optimize networks for their use cases that are relevant to their business and cannot offer customized solutions to their customers. The net result is legacy networks that are: difficult to optimize, difficult to customize, costly to run and inefficient.
SDN can be confusing because it’s used to create workload aware networks, so it has different implications depending on whether you’re running a Fortune 500 enterprise data center, a telecom carrier network, or some other application. Also SDN creates a set of abstractions for programming a data network, which can be subtle concepts. Goldman Sachs were one of the early adopters of this technology, dating back to before it was even called SDN.
In the simplest possible terms, SDN is a higher level of abstraction and entails the decoupling of the control plane from the forwarding plane and offloading its functions to a centralized controller. Rather than each node in the network making its own forwarding decisions, there is one centralized software-based controller (likely running on commodity server hardware) that is responsible for instructing subordinate hardware nodes on how to forward traffic. Because the controller effectively maintains the forwarding tables on all nodes across the network, SDN-enabled nodes don't need to run control protocols among themselves and instead rely upon the controller to make all forwarding decisions for them. The network, as such, is said to be defined by software running on the controller.
A centralized system controller that can view the entire topology can then make more informed decisions about the network flow
Whereas in a legacy network a node can only see other nodes that it is connected to, an SDN controller has a view of the entire network topology that allows it to provide better quality of service and optimize its configuration according to dynamic requirements. However there are still questions that need to be answered in the event of the controller losing connectivity to one or several switches, so there is potential for hybrid deployments where non-SDN switching could be used as a backup.
We don’t need to reinvent all the functions of an existing network, but if SDN allows us to perform some functions better, faster, or more efficiently, then it has tangible value. Due to the fact that software is providing the commands, this means that the network can be programmed. And as all software engineers know, anything programmable can be automated and later optimized. It’s even better if SDN allows us to do something innovative, something that wasn’t economically practical or technologically feasible until now. Therein lays the real benefit of SDN; moving from a static, ‘one size fits-all’ style to a network that is more agile and flexible. Because it is easier to service and update, it also allows you to offer new features and functions that would be either too difficult or expensive to include in a legacy data center network.
Just as the new version of Android Lollipop or iOS will run best on the mobile devices that are tailored to its design, the same is true for SDN. The rise of this new level of software-based abstraction actually means that the hardware involved in these networks needs to adapt as well to provide a truly integrated solution. For example, the ARM® CoreLink™ CCN Cache Coherent Network family are all highly configurable and provide balanced service for both low latency and high bandwidth data streams, which enables scalable system coherency in heterogeneous processor systems. Similarly, the ARM CoreLink GIC-500 Generic Interrupt Controller and ARM CoreLink MMU-500 System Memory Management Unit both support the virtualization that is needed to get the most out of the software. With the release of IP blocks like these that are built with SDN in mind, it makes it easier for infrastructure architects to make the shift from traditional legacy networks.
An The specified item was not found. white paper goes into some detail on the use cases of SDN, in particular highlighting that it is “highly applicable to carrier networks since they are typically composed of heterogeneous hardware platforms and protocols, and offer several benefits to the unified carrier-datacenter network”. In recent months there has been a number of announcements from ARM partners increasing the momentum in the shift to SDN for infrastructure solutions, such as HP, Freescale and Broadcom.
The good news is that network equipment OEM's now have a range of options to choose from when making their choice of what medium to use to realize their equipment designs. There are already a range of ASSP silicon providers who provide SOC designs for a whole range of applications from enterprise networking through wireless infrastructure to core infrastructure networking applications. Announcements like the one from The specified item was not found.allow OEMs to benefit from integration of diverse functions and target extremely high performance compute subsystems that are ARM ISA compliant.
The SDN revolution that was on everybody’s minds a year ago is quietly gathering pace. Presently, its development is focused heavily on the large data center and virtualization space with some useful applications announced. It looks like it could very well evolve into a useful tool for the enterprise and service provider space in the near future, and I for one will be an interested observer to see what other applications will be found for this technology.
Hi Eoin, thanks for the SDN overview! The new CCN products that Jeff wrote about in Extending the CoreLink Cache Coherent Network Family are an important part of the ARM solution. Providing up to 48 coherent ARM cores certainly offers a lot of compute capacity for SDN.