SDN and NFV and WAN Modernization

The role of network infrastructure is seeing a rapid change from the historical perspective of component by component design to one where those capabilities are created in mixed modes of pure hardware (let's call this the classical model), hardware and software (let's call this hybrid networking) and software alone (defined as Network Function Virtualization or NFV).

Each of these can be programatically defined with increasing software definition as the capabilities move toward NFV.  So, one may have both a NFV instance or instances of functionality AND software defined functionality.

SDN and NFV vs Classical WAN

Using the picture above, Classical site level networking introduces discreet hardware devices to provide specific service capabilities in at the location.  These could and do typically include routers, switches, firewalls, load balancers, wan optimization devices and wireless controllers.

These also have a very low degree of unified Software Definition, but will typically have high performance.

In the case of the Software Defined WAN (Cloud WAN, SD-WAN, etc), those functions typically assigned to discreet hardware at the site are virtualized into their Network Function, yes, Network Function Virtualization.  Integration of these virtual services with a management and control plane provides a key element in addressing Software Defined WAN.  Each element is intended to operate in unison in a pre-determined way to provide the site level WAN Service as well as other services for the site.

This would have a much higher degree of Software Definition.

The limitations of this method may include sufficient processing power (CPU) and processing memory.  Where, as an example, an x86 server is used to provide the host for virtualization, there may also be a critical limit to the capabilities of the box relative to performance.  Where network hardware typically uses well defined processes, in ASICs to amplify the performance, much of the work done within a virtualization system is accomplished in software.

This means that there will be a performance difference, escalating as the number and type of NFV services that are applied to the same server host.  Expect more dramatic drops in performance when services like firewall rules increase significantly as this may cause more software lookups and therefore slower packets per second.

This is not static though.  Performance of NFV services will continue to increase and become optimized in software.  Performance of x86 hardware is absolutely guaranteed to continue to increase in performance and applicable memory per CPU.  Network card vendors are building addressable hardware functions within the network interface.  Parts of the NFV services may be broken out to optimize performance.

The recommendation, look at the specs and decide what you want/need to do.  Where necessary, break out to a hybrid network solution to solve today's problems and look to the future where these functions integrate even tighter with better performance.