Although cloud and network service providers might not be ready to deploy software-defined networking throughout all parts of their networks today, many agree that some degree of virtualization, like network functions virtualization, will allow for more flexible traffic flow management and efficient use of resources within their complex networks.
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Network functions virtualization (NVF) -- an initiative proposed by several Tier 1 network operators and currently under development by the European Telecommunications Standards Institute's Industry Specification Group -- replaces traditional network devices with software running on commodity servers. It is designed to eliminate the need for dedicated network devices, such as routers, switches and firewalls. Moving networking functions from hardware to commodity servers helps providers avoid overbuying equipment and underutilizing resources.
Nearly 55% of service providers believe that software-defined networking (SDN) is not necessary for deploying a programmable network, according to a recent SearchCloudProvider survey of more than 200 service providers. Because network virtualization and NFV don't require providers to completely re-architect their networks, they offer a more approachable strategy for simplifying the deployment of core network services.
Virtualized infrastructure: More flexibility for providers
Cloud and network service providers may be more comfortable with the idea of NFV over SDN because while SDN was created by network architects, NFV was developed by a consortium of carriers, including Verizon, AT&T and BT. Many service providers are at least beginning to work with some flavor of network virtualization, if not SDN, to help with their large-scale environments.
Phoenix NAP, a Phoenix-based colocation and Infrastructure as a Service provider uses network virtualization, having deployed VMware’s vSphere technology for its public cloud services and vCloud Director technology within its virtual private data center and managed private cloud products.
Network virtualization has given Phoenix NAP more flexibility, as well as the ability to accommodate more customers, said William Bell, vice president of product development for cloud and enterprise services at Phoenix NAP. "In the past, we have had X amount of networks, which determined we could have X amount of customers, and those limits were hard and fast inside the data center," he said. "Network virtualization really tears down those walls, and we were able to scale out instead of scaling up."
While some providers claim to be deploying one programmable networking concept over the other, SDN and NFV are still in their adolescence, and the terms can be used interchangeably, Bell said. "There is no difference," he said. "Some providers are trying to differentiate themselves by using one of the other, depending on what they have built. An overlay system is usually just called virtualization, but if they have some complex controller software, they might call it SDN."
Network functions virtualization, SDN: Is there a difference?
Not everyone agrees on the degree of difference between SDN, network virtualization and NFV, but there are technical differences between an SDN implementation and certain kinds of virtual network deployments, said Paul Parker-Johnson, practice lead for cloud computing and virtual infrastructure technologies at ACG Research.
"[Virtual Extensible LAN] is an example of level-2 and -3 overlay virtual networks that are done completely in software and are very flexible to deploy, but are not SDN-based," he said. "The network … is virtualized but is not implemented using the design of 'control plane controller' and 'common intermediate protocol for data plane communications' that is used in SDN."
More on network function virtualization
SDN vs. network virtualization: Q&A with Martin Casado
Network functions virtualization primer: Software devices step in
How network functions virtualization will change architecture
The difference between network virtualization and SDN is nuanced, but it's less pronounced than the difference between NFV and SDN, Parker-Johnson said.
While some providers and vendors are staying loyal to their current networking architecture, the best way to achieve network programmability depends on the provider's environment, said Brad Casemore, research director at Framingham, Mass.-based IDC. Factors to consider include the applications running, existing technology investments and available resources.
"There isn’t a one-size-fits-all approach -- some will want to adopt SDN to achieve programmability, and some will not. SDN isn't the only way," he said.
But while the lines between NFV and SDN are sometimes blurred, NFV is complementary to SDN, and there is room for both approaches within the same environment, ACG's Parker-Johnson said.
Although network virtualization and NFV can be achieved without the use of SDN, SDN can facilitate and enhance network performance. On the other hand, NFV can support SDN software on its infrastructure while still eliminating the need for dedicated hardware.
"[Providers] are interested in SDN and NFV, [and] frameworks for implementing each are being furiously developed," Parker-Johnson said. "Over time, a more consistent deployment pattern will emerge, but for now it is [in] early-stage development, adoption and application."