In computing, Network Virtualization is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization.
Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to the software containers on a single system. Whether virtualization is internal or external depends on the implementation provided by vendors that support the technology.
* 1 Components of a virtual network
* 2 External network virtualization
o 2.1 Examples of external network virtualization
* 3 Internal network virtualization
o 3.1 Examples of internal network virtualization
* 4 Combined internal and external network virtualization
* 5 Network virtualization Initiatives
* 6 See also
* 7 References
 Components of a virtual network
Various equipment and software vendors offer network virtualization by combining any of the following:
* Network hardware, such as switches and network adapters, also known as network interface cards (NICs)
* Networks, such as virtual LANs (VLANs) and containers such as virtual machines (VMs) and Solaris Containers
* Network storage devices
* Network media, such as Ethernet and Fibre Channel
Following is a survey of common network virtualization scenarios and examples of vendor implementation of these scenarios.
 External network virtualization
Some vendors offer external network virtualization, in which one or more local networks are combined or subdivided into virtual networks, with the goal of improving the efficiency of a large corporate network or data center. The key components of an external virtual network is the VLAN and the network switch. Using VLAN and switch technology, the system administrator can configure systems physically attached to the same local network into different virtual networks. Conversely, VLAN technology enables the system administrator to combine systems on separate local networks into a VLAN spanning the segments of a large corporate network.
 Examples of external network virtualization
Cisco Systems Service-Oriented Network Architecture enables external network virtualization through use of the network switch hardware and VLAN software. In this scenario, systems that are physically connected to the same network switch can be configured as members of different VLANs.
Hewlett Packard has implemented external network virtualization through their X Blade Virtualization technologies. Chief among these is Virtual Connect, which allows system administrators to combine local area networks and storage networks into a singly wired and administered network entity.
 Internal network virtualization
Other vendors offer internal network virtualization. Here a single system is configured with containers, such as the Xen domain, combined with hypervisor control programs or pseudo-interfaces such as the VNIC, to create a “network in a box.” This solution improves overall efficiency of a single system by isolating applications to separate containers and/or pseudo interfaces.
 Examples of internal network virtualization
Citrix and Vyatta have built a Virtual Network Stack combining, Vyatta's routing, firewall and IPsec VPN functionality with Citrix Netscaler load balancer, Branch Repeater WAN optimization and Access Gateway SSL VPN. The vNetworkStack project is defining entire virtualized network architectures for branch offices, datacenters and cloud computing environments.
OpenSolaris network virtualization features (see OpenSolaris Network Virtualization and Resource Control) enable the "network in the box" scenario. The features of the OpenSolaris Crossbow Project provide the ability for containers such as zones or virtual machines on a single system to share resources and exchange data. Major Crossbow features include VNIC pseudo-interfaces and virtual switches, which emulate network connectivity by enabling containers to exchange data without having to pass that data onto the external network.
Microsoft Virtual Server uses virtual machines such as those provided by Xen to create a network in the box scenario for x86 systems. These containers can run different operating systems, such as Windows or Linux, and be associated with or independent of a system's NIC.
 Combined internal and external network virtualization
Some vendors offer both internal and external network virtualization software in their product line. For example, VMware provides products that offer both internal and external network virtualization. VMware's basic approach is network in the box on a single system, using virtual machines that are managed by hypervisor software. VMware then provides its VMware Infrastructure software to connect and combine networks in multiple boxes into an external virtualization scenario.