Your Questions Answered: Software-Defined Networks

Experts talk about infrastructure, security concerns, and potential military applications

6 January 2015

Image: iStockphoto

Our December special report covered software-defined networks, a technology that will support the changing nature of future networks. SDNs are networks of equipment that decouple hardware—such as forwarding IP packets—from software and executes such software not necessarily in the equipment, but either in the cloud or in clusters of distributed IT servers.

Responding to readers’ questions about the emerging technology are IEEE Member Antonio Manzalini, chair of the IEEE Software Defined Networks Initiative, and IEEE Fellow Prosper Chemouil, chair of the initiative’s conference subcommittee. Manzalini is senior manager at the Future Centre in Turin, Italy, which is part of the Italian telecommunications giant’s strategy and innovation department. He is in charge of investigating SDNs, network functions virtualization (NFV), and 5G technologies. Chemouil is director of the Future Networks program at Orange Labs, in Paris, where he is involved with the design and management of future networks and technologies.


In SDNs, the network itself is part of the network control infrastructure. Given that, how will these architectures hold up in the face of massive congestion?

Manzalini: The network itself is not necessarily part of the network control infrastructure. As a matter of fact, in SDNs data and control planes could be logically and physically decoupled. Traffic engineering and the orchestration of functionalities will help tame the risk of massive congestions.

Chemouil: Network management capabilities offered by the real-time features of SDNs may also help in preventing and addressing overload and congestion issues, in particular through smart traffic admission control.


What are the security issues associated with SDNs?

Chemouil: As some have pointed out, there is risk that a centralized SDN controller will be a single point of attack or failure. Various security proposals have considered setting up multiple SDN controllers, either in a distributed way or in a hierarchical structure. As a consequence, the placement of SDN controllers is being addressed by the research community.


How will SDNs facilitate the Internet of Things?

Manzalini: In general, it can be argued that SDNs and NFV are accelerating the transition towards a “digital society” and a “digital economy,” where the telecommunications infrastructures and more pervasive and embedded processing and storage capabilities will become a “nervous system” reaching terminals, drones, robots, and smart things such as machines and cars. With SDNs and NFV, the border between the telecom infrastructure and what connects to the “things” will blur.


How do SDNs relate to fog or network computing?

Manzalini: SDNs and NFV are related to cloud, fog, and network computing because they are just different expressions of the same systemic trend called “softwarization.” This trend has been and is triggered and steered mainly by ultra-broadband diffusion—that is, high bandwidth and low latency connections—

and the IT techno-economic drivers, which includes increasing performance of chipsets at continuously decreasing costs. Softwarization is impacting not only the telecommunications infrastructures, but also several other segments and industries in which we’re already witnessing a deep introduction of information and communications technology systems for digitizing and automating processes.

Chemouil: SDNs could be considered a piece of the whole architecture regarding fog or mobile edge computing, as these are new expressions for leveraging virtualization and cloud networking capabilities.


Why is there a need for SDNs, given that we have plenty of social networks in addition to existing computer networks?

Manzalini: SDNs and NFV are expected to reduce costs of telecommunications infrastructures and to introduce greater flexibility like programmability through application program interfaces and better customization that could enable new business models. More than a need, SDNs and NFV will lead us to softwarization and bring down costs.


What is the expected latency of SDNs?

Manzalini: As in current telecommunications infrastructure, SDNs’ latency will include a number of contributions from the transmission latency, which has a physical limit related to the speed of light, as well as switching/routing latency; middleboxes, which inspect, transform, and manipulate traffic; and what are known as application latencies. Overall latency will depend on the architectures and physical topologies of SDNs—centralized versus distributed and the processing performances of IT resources. The long-term goal is to bring down overall latency to some unit of milliseconds.


What are the military applications of SDNs?

Manzalini: Applications for controlling drones and robots are two examples. In general, the availability of huge amounts of cloud processing and storage, interconnected by flexible and fast SDNs, will create a pervasive machine intelligence able to morph space-time physical dimensions, and the direct physical presence of humans will be required less and less to perform certain jobs or tasks.


When is it realistic to see SDN-enabled network equipment in real deployment, such as in mobile backhaul?

Manzalini: There might be different strategies of SDN deployment depending on several variables, including the availability of standards, the adoption of operation processes capable of supporting SDN equipment, the foreseen models for business sustainability, and regulatory issues.

Chemouil: Today the deployment of SDNs is tightly linked to the maturity of NFV, which is seen as a priority by telecommunications and network operators. It is anticipated that solutions will be available in the next few years, opening up pathways to massive deployment.

What will be the price of SDN switches compared to current equipment?

Manzalini: There are expectations that the prices will be much lower given that they might be based on standard hardware and open-source software. It is impossible to predict prices partly due to the fact that they will depend on the specific type of SDN switch.  


What are the chances that SDN happens without NFV?

Manzalini: SDNs and NFV are mutually beneficial but are not dependent on each other. Network functions can be virtualized and deployed without an SDN being required and vice versa. SDNs and NFV, whether independent or combined deployment, will depend on the availability of standard interfaces, the related pieces of equipment, and the required management or orchestration methods and systems. The level of adoption will also depend on business sustainability and service market dynamics.

Chemouil: The telecommunications industry sees NFV as a shorter-term opportunity to lower operating expenses. This is why both SDNs and NFV are now progressing in parallel, though SDN solutions have been addressed ahead of the NFV paradigm.

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