What is the difference between SDN and NFV?
Network function virtualization (NFV) and software-defined networks (SDN) are two closely related technologies that often exist together, but not always. An SDN can be considered a series of network objects (such as switches, routers, firewalls) that deploy in a highly automated manner. The automation may be achieved by using commercial or open source tools customized according to the administrator's requirements. A full SDN may only cover relatively straightforward networking requirements, such as VLAN and interface provisioning.
In many cases, SDN will also be linked to server virtualization, providing the glue that sticks virtual networks together. This may involve NFV, but not necessarily. NFV is the process of moving services, such as load balancing, firewalls and IPS, away from dedicated hardware into a virtualized environment. This is, of course, part of a wider movement toward the virtualization of applications and services.
Functions such as caching and content control can easily be migrated to a virtualized environment but won't necessarily provide any significant reduction in operating costs until some intelligence is introduced. This is because a straight physical to virtual, from an operational perspective, achieves little beyond the initial reduction in power and rack-space consumption. Until some dynamic intelligence is introduced with an SDN technology, NFV inherits many of the same constraints as traditional hardware appliance deployments, such as static, administrator-defined and managed policies.
A good example is virtualized application delivery controllers (ADCs). With careful configuration, it is possible to react to the network state and spin up or down application servers as demands rise and fall. However, traditional hardware deployments have been able to do this for a while, and the configuration is very static; it doesn't cater to the scenario where the ADC itself becomes overloaded or an additional application needs to be brought into production quickly. With SDN features driving NFV, several useful things start to happen. The network can react when things need to change at the micro and macro level. An additional instance can be provisioned in a cluster of virtualized ADCs as the load increases, and production applications can easily be cloned and re-deployed in a development environment. The potential is endless.
So it's perfectly possible to have NFV without the inclusion of a full-blown SDN. The two are often deployed together, and an SDN that drives NFV is a very powerful combination.
Neither NFV nor SDN are turnkey solutions in early 2014 -- a great deal of integration and policy design still need to happen. This can become a reality for many enterprises, but the harness is not entirely in place. That said, the tools are rapidly evolving, and many vendors are bringing technologies to market that support SDN or NFV deployments. Ultimately, the implementation of either or both technologies will be driven by the business needs.
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