On March 30, 2013, I published a blog on SDxCentral called “NFV and SDN: What’s the Difference?” Both NFV and SDN were very new at the time. We kept getting asked what the difference between them was, so I wrote that blog to provide an answer. I think that the original blog is still accurate and relevant, but two years later it is time for an update. So, what has changed since March 2013 (besides my photo)?

NFV and SDN Are Recognized to Be Separate But Complementary
Remember, in March of 2013 NFV was brand new. SDN had been around for a couple of years, but its audience was limited. At the onset, there was general confusion around the similarities and differences between NFV and SDN (hence the reason for the original post). Now, both are gaining traction in the marketplace.

The road has been a bit easier for NFV, as it brings some compelling use cases with easily measured benefits. The promise of SDN is broader, but requires a larger investment and slower payback. Even so, service providers are now formulating plans to deploy SDN in conjunction with NFV.

Despite the fact that SDN and NFV are clearly defined, some folks are trying to conflate them. I think that it is best to be precise in our terminology and recognize the distinct natures of SDN and NFV. Speaking of precise . . .

NFV Is Clearly Defined and Generally Understood
Back in the spring of 2013, the ETSI NFV ISG was just getting started and NFV was largely undefined. Now, the ISG has published 17 specifications on NFV, covering topics ranging from terminology to architecture, to service quality metrics, to management and orchestration (MANO) and proofs of concepts (PoCs).

The PoCs have been especially interesting. Since that time, there have been a total of 34 approved ETSI PoCs. Since each PoC has to have a service provider participating, the large number of PoCs is a concrete proof point of the level of interest in NFV.

Orchestration Has Emerged as the Latest Hot Topic
When the original blog came out, orchestration was barely a glimmer on the horizon. Now, everybody and their brother are claiming to provide orchestration. With respect to SDN and NFV, I believe that orchestration is well defined. Specifically, it is defined within the MANO function defined in ETSI NFV. The following image is derived from Figure 5.1 from the ETSI specification “Network Functions Virtualisation (NFV); Management and Orchestration” (ETSI GS NFV-MAN 001 V1.1.1 (2014-12)).).

NFV-ArchetictureAs shown, the NFV orchestration (NFVO) block interfaces between the OSS/BSS systems and the subtending VNF manager (VNFM) block. Per the ETSI MANO document, the NFVO handles the following.

5.4.1 NFV Orchestrator (NFVO)

The NFV Orchestrator has two main responsibilities:

  • The orchestration of NFVI resources across multiple VIMs, fulfilling the resource orchestration functions described in clause 4.2
  • The lifecycle management of network devices, fulfilling the network service orchestration functions, as described in clause 4.4.

The challenge that I find is this: although true NFV orchestration is clearly outlined above, people in the industry are not necessarily adhering to this definition. Simple configuration of physical network elements using protocols such as OpenFlow or NETCONF is NOT NFV orchestration, as it does not meet these requirements.

SDN Is Now Being Pursued by Communications Service Providers (CSPs)
Back in 2013 NFV SDN was nowhere in CSP networks. The prospect of deploying new SDN-enabled equipment, along with new software systems, promised to be an expensive and daunting path forward. After two years of work, we are now seeing the availability of much more evolutionary approaches that minimize disruption and initial cost.

At the same time, there is recognition that the control and automation aspects of SDN greatly benefits NFV. As a result, service providers are now formulating plans to deploy SDN in telco networks.

NFV and SDN – Still Different, But More Coupled Than Ever
After two years of massive industry innovation, we see that SDN and NFV are still different. NFV is very much about moving from appliances to software running on servers, and SDN provides a means to separate control and data and then program the behavior of both. Both NFV and SDN have advanced from the drawing board to trials and early trials. An analyst told me the other day that CSPs have moved from asking “what?” and “why?” about SDN and NFV to asking “how?” indicating their shift in understanding and interest. The most successful deployments will be those that can effectively utilize the benefits of both SDN and NFV.