SDN & NFV: Dynamic Duo Of Next-Gen Networks?

The relationship between SDN and NFV may be indirect today, but over time the technologies could become inseparable. Find out why.

Jim Metzler

February 19, 2015

4 Min Read
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For the last few years, software-defined networking (SDN) has been the hottest topic in the industry. And over the past year, interest in network functions virtualization (NFV) has been growing, among service providers and enterprise IT organizations alike. But there is confusion about the relationship between SDN and NFV. Is there a tight bond between these two architectural approaches, or are they ships in the night?

Up until a year ago the general feeling was that SDN and NFV were complementary technologies and that neither one had a tight dependency on the other. That view began to change in March, 2014, when the Open Networking Foundation (ONF) and the European Telecommunications Standards Institute (ETSI) announced they signed of a Memorandum of Understanding (MOU). As part of the announcement, the ONF and ETSI said, "Together the organizations will explore the application of SDN configuration and control protocols as the base for the network infrastructure supporting NFV, and conversely the possibilities that NFV opens for virtualizing the forwarding plane functions."

In conjunction, the ONF released the OpenFlow-Enabled SDN and NFV Solution Brief. That document discussed how OpenFlow-enabled SDN can meet the need for automated, open, and programmable network connectivity to support some of the ETSI-defined use cases, such as network functions virtualization infrastructure as a service, and virtual network function forwarding graphs.

When interviewed for this article, Marc Cohn, chair of the Market Education Committee for ONF, said that it is very difficult to create a dynamic software environment such as NFV without the type of dynamic network environment that is enabled by SDN. In his words, "the traditional approach of over-provisioning the network will not work." Because of that, Cohn also believes that SDN will have to make significant progress before NFV will be broadly adopted.

In a recent white paper, ETSI expressed its belief that NFV and SDN are highly complementary efforts. The ETSI view is that both efforts are seeking to leverage virtualization and software-based architectures to make network infrastructures more cost-effective and agile, better accommodating the dynamic nature of workflows.

While ETSI states that NFV can be implemented using a non-SDN infrastructure, the ETSI vision is that NFV and SDN will increasingly be intertwined into a broad, unified, software-based networking paradigm based on the ability to abstract and programmatically control network resources.

Some of the ways that ETSI believes that NFV and SDN complement each other include:

  • The SDN controller fits well into the broader concept of a network controller in an NFV-infrastructure (NFVI) network domain as defined in ETSI's NFV architectural framework.

  • SDN can play a significant role in the orchestration of the NFV Infrastructure resources, both physical and virtual, enabling functionality such as provisioning, configuration of network connectivity, bandwidth allocation, automation of operations, monitoring, security, and policy control.

  • SDN can provide the network virtualization required to support multi-tenant NFVIs. 

  • Forwarding graphs can be implemented using the SDN controller to provide automated provisioning of service chains, while ensuring strong and consistent implementation of security and other policies.

  • The SDN controller can be run as a virtual network function (VNF), possibly as part of a service chain including other VNFs. For example, applications and services originally developed to run on the SDN controller could also be implemented as separate VNFs.

My recently published report, The 2015 Guide to SDN & NFV, included the results of a survey taken by 135 IT professionals, most of whom work in enterprise IT organizations. One of the survey questions asked the respondents to indicate the relationship that their company sees between SDN and NFV. A large majority of survey respondents (61%) indicated that SDN and NFV are complementary activities in that each can proceed without the other, but the value of each activity may be enhanced by the other activity. A quarter of respondents said that, at least in some instances, NFV requires SDN. Only 6% said their company views SDN and NFV as totally independent activities.

The beginning of this article asked of whether there is a tight bond between SDN and NFV. Given the embryonic state of SDN and NFV development and implementation, it shouldn't be surprising that the answer to that question is a definite no. However, the ONF and ETSI, which are two of the key organizations driving the development of SDN and NFV, believe that there are NFV use cases whose value is significantly enhanced by SDN. The majority of IT organizations share that view.

Given the current trajectories of SDN and NFV, it is highly likely that over time the ETSI vision of NFV and SDN intertwining into a broad, unified, software-based networking paradigm based on the ability to abstract and programmatically control network resources will come true. At that time, we will no longer differentiate between SDN and NFV.

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About the Author(s)

Jim Metzler


Dr. Metzler has worked in many positions in the networking industry. This included creating software tools to design customer networks for a major IXC; being an engineering manager for high-speed data services for a major telco; being a Product Manager for network hardware; managing networks at two Fortune 500 companies; directing and performing market research at a major industry analyst firm; and running a consulting organization. Jim's current interests include application delivery, software defined networking, and network functions virtualization. He has published the ebooks "The 2014 Guide to Application and Service Delivery" and "The 2014-2015 Guide to Software Defined Networking and Network Function Virtualization."

Jim holds a Ph.D. in Numerical Analysis from Boston University. He has been on the faculty of several universities, including Bentley University, Northeastern University, and Drew University. He co-authored the book Layer 3 Switching: A Guide for IT Professionals, has written for numerous publications, and is a frequent speaker at conferences and seminars.

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