Understanding How SDN and NFV Can Work Together

As software-defined networking and network function virtualization begin to take hold in the enterprise, it's worth examining each concept to see how they complement each other. The end result: More generic network hardware and more open software.

For 2013 and beyond, two of the most interesting and most used networking acronyms — and underlying concepts and technologies — have to be SDN (for Software Defined Networking) and NFV (for Network Function Virtualization).

Though many IT pros are inclined to stand these two concepts up against each other, as in SDN vs. NFV, these two revolutionary networking developments don't represent an either-or proposition. In fact, it instead looks very much like a both-and deal — as in, "both SDN and NFV are likely to find a place in modern enterprise networks and carrier infrastructures."

Though both terms are subject to interpretation, it's still worthwhile to proffer definitions to establish what SDN and NFV are about, where they originate and how SDN and NFV differ.

SDN: Separating Network Control Logic from Network Hardware

SDN comes out of large-scale IP infrastructures where network designers and implementers sought to simplify traffic management and achieve operational efficiencies by establish and exercising central control over packet forwarding. Over time, SDN has also come to describe an open networking environment where elements such as switches, servers and storage may be configured and managed centrally while running on standard hardware components.

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Software Defined Networking

The guiding principle behind SDN remains the separation of network control logic from the physical routers and switches that forward traffic from individual network nodes, based on a real-time view of the network as a whole. In fact, the Open Networking Foundation (a nonprofit consortium focused on SDN, defines it as an architecture that migrates control "into accessible computing devices" designed to enable "the underlying infrastructure to be abstracted for applications and network services, which can treat the network as a logical or virtual entity."

In essence, this means SDN control software sits atop a physical infrastructure layer composed of networking devices, with which it communicates via a control plane interface such as OpenFlow.The idea is to turn networks into flexible, programmable platforms to optimize resource utilization, making them more cost effective and scalable. By providing APIs for business applications and services, SDN also promises to recast information technology by integrating cloud-based services and capabilities, and high-speed networking, into the computing fabric.

NFV: Virtualization for Key Network Functions

NFV, on the other hand, comes from service providers interested in facilitating deployment of new network services by virtualizing networking devices and appliances, not through ongoing proliferation of physical devices to fill specialized roles such as routing, switching, content filter, spam filter, load balancer, WAN acceleration and optimization and unified threat management, and so forth. Participants assembled to create an Specification Group for NFV, whose member list includes a majority of major carriers and providers worldwide.

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The self-professed goal of the organization is to "define the requirements and architecture for the virtualization of network functions." Its predictable aims, dear to all service providers, are helping customers reduce capital and operations expenses, speeding time to market for service elements and providing flexible, agile solutions delivered in software running on industry-standard server hardware elements.

Ultimately, NFV is about virtualizing IT resources in software so that virtual implementations may be used to provide important network functions, rather than requiring the presence of one or more specialized physical devices. These virtual devices appear and behave like their physical counterparts on the networks they serve without the need for individual devices to fill their various specialized functions.

At present, the primary focus for NFV in today's marketplace targets the following niches:

  • Virtual Switching, or physical ports that link to virtual ports on virtual servers, where virtual routers employ virtualized IPsec and SSL VPN gateways
  • Virtualized Network Appliances, where network functions that could employ dedicated devices can instead employ virtualized appliances for a range of specialized functions
  • Virtualized Network Services, which provide software-based network monitoring and management services, including traffic analysis, network monitoring and alerting, load balancing and quality or class of service handling
  • Virtualized Applications, which deliver network-optimized frameworks and APIs for cloud applications to support an increasingly mobile or BYOD-based user population

SDN, NFV More Complementary Than Competitive

To the relief of all parties involved — primarily the enterprises and consumers of high-end networking on the SDN side, and the service providers who assembled themselves to get behind virtualized network functions on the NFV side — SDN and NFV dovetail nicely.

Together, in fact, they represent a path toward more generic network hardware and more open software, where the centralized control and management decreed in SDN can in part be realized through the virtualized functions and capabilities that come from NVF. This applies especially for network management applications and services for monitoring, management, traffic analysis, load balancing and so forth.

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Both SDN and NFV capitalize and depend heavily upon virtualization to enable their respective capabilities — and to deliver upon their promises to separate connections and packet handling from overall network control (SDN) while combining and consolidating specialized functions and capabilities on standard hardware elements (NFV).

Adoption of what Tom Nolle calls a "software-overlay network model" means that, in a conglomeration of cloud-hosted virtual functions, NFV makes use of services as tenants atop NFV infrastructures. Here, tunnels and virtual switches isolate virtual functions to prevent interaction, stymie malicious snooping or attack, and link to cloud-based virtual network interfaces such as those described in OpenStack Neutron.

It appears, then, that the kinds of functions that NFV seeks to deliver work well within the framework defined for SDN, and that services defined for NFV will help provide the necessary abstraction and separation of the network control and data/packet planes.

It might be serendipity at work, but this combination appears to offer potent potential for the next revolution in networking. At any rate, it will be fascinating to see how things play out in 2014 and beyond.

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