Network virtualization is a versatile technology. It allows you to combine multiple networks into a single logical network, parcel a single network into multiple logical networks and even create synthetic, software-only networks between virtual machines (VMs) on a physical server.
Virtual networking typically starts with virtual network software, which is placed outside a virtual server (external) or inside a virtual server -- depending on the size and type of the virtualization platform.
Any virtual networking that takes place outside of a virtual server is called external network virtualization. This occurs when multiple physical LANs are aggregated into a single logical LAN, or when a single physical LAN is parceled out into multiple virtual LANs (VLANs). External network virtualization uses virtual network software such as Hewlett-Packard Virtual Connect and involves network switches, network adapters, servers, network storage devices and the Ethernet or Fibre Channel media that interconnects these hardware devices.
In internal network virtualization, virtual network software can emulate network connectivity within the server and allow VMs hosted on that server to exchange data. It might seem trivial, but the isolation that a virtual network provides can be useful. Eliminating the need to pass data on an external network can improve performance and bolster security for associated VMs.
Some virtual platforms support both internal and external network virtualization. VMware is one example; its platform supports internal network virtualization through the native hypervisor and uses additional software to support external virtualization.
Certain vendors tout virtualization and networking as a vehicle for additional services -- not just as a way to aggregate and allocate network resources. For example, it's common practice for a network switch to support security, storage, voice over IP (VoIP) and other advanced network services.
Regardless of the approach, managing virtual network software can be extremely challenging. It can be difficult, even impossible, to keep track of the multiple services and virtual networks running within the physical LAN. Careful documentation, clear workflow procedures and comprehensive management tools are vital for proper virtual networking management.
Several initiatives will influence the proliferation of network virtualization in the future. These include, but are not limited to, the Global Environment for Network Innovations, Future Internet Research and Experimentation, the AKARI Architecture Design Project and Federated E-infrastructure Dedicated to European Researchers Innovating in Computing Network Architectures (FEDERICA).