Network virtualization is a method used to combine computer network resources into a single platform, known as a virtual network. It is achieved by software and services that allow the sharing of storage, bandwidth, applications, and other network resources. The technology utilizes a method similar to the virutalization process used to simulate virtual machines within physical computers. A virtual network treats all hardware and software in the network as a single collection of resources, which can be accessed regardless of physical boundaries. In simple terms, network virtualization allows each authorized user to share network resources from a single computer.
There are two forms of network virtualization, external and internal. External virtualization generally combines multiple networks — or parts of networks — into a single virtual entity. Internal virtualization provides system-wide sharing and other network functionality to the software containers, which act as hosting environments for the software components of the network, on a single physical system. The external variety is the most commonly used method to create virtual networks. Vendors that distribute these virtualization tools generally offer either one form or another.
Network virtualization is not an entirely a new concept. In fact, virtual private networks (VPNs) have been widely used by network administrators for years. Virtual local area networks (VLANs) also represent a common variation of network virtualization. Both serve as examples of how significant advancements in computer connectivity methods have made it possible for networks to no longer be restricted by geographical lines.
Organizations may use network virtualization for a number of reasons, but many do so because it allows for customization and ease of network use. Virtualization can provide customized access that allows administrators to allocate critical network services, such as bandwidth throttling and Quality of Service (QoS). It can also provide consolidation by allowing a multitude of physical networks to be combined into a single virtual network, allowing for streamlined and simplified management.
Network virtualization does have some disadvantages. Perhaps the most notable is that, similar to server virtualization, it can bring forth a higher degree of complexity, in addition to performance overhead. It also tends to call for a higher skill set on the part of network administrators and users.
Successful network virtualization requires thoughtful planning. This is primarily because it has not been as widely deployed as traditional hardware virtualization, a concept that dates back to the 1960s. Many organizations elect to plan and implement the technology in phases, often deciding to begin with the non-essential aspects of the IT environment. This strategy is often used to minimize disruptions, and enable the organization to determine the value in virtualization before deploying it across the entire network.