OVF has generally been positively received.[6] Several virtualization players in the industry have announced support for OVF
Product:
Virtual BOX
Red Hat
XenServer
IBM Power
IBM SmartCloud
Open Node Cloud Platform
Oracle VM
rPath
SUSE Studio
Microsoft System Center Virtual Machine Manager
Amazon Elastic Compute Cloud

OVF? OVA? VMDK? – File Formats and Tools for Virtualization
Virtual Appliances may or may not have full-blown operating systems supporting the applications, but the key thing is that they are able to run directly on a hypervisor (VMWare ESX, XenServer, Hyper-V, etc.)
“GitHub Enterprise” that allows a business to deploy their own copy of the GitHub platform within their network; GitHub Enterprise is distributed as virtual appliance.

File Formats for Virtual Machines
Open Virtualization Format (OVF)
The OVF Specification provides a means of describing the properties of a virtual system. It is XML based and has generous allowances for extensibility (with corresponding tradeoffs in actual portability). Most commonly, an OVF file is used to describe a single virtual machine or virtual appliance. It can contain information about the format of a virtual disk image file as well as a description of the virtual hardware that should be emulated to run the OS or application contained on such a disk image.
Open Virtual Appliance (OVA)
An OVA is an OVF file packaged together with all of its supporting files (disk images, etc.). You can read about the requirements for a valid OVA package in the OVF specification. Oftentimes people will say “an OVF” and really mean “an OVA.”

Importing OVF File is easy and make the installation more better

Network Virtualization
Network virtualization is the complete reproduction of a physical network in software. Applications run on the virtual network exactly the same as if on a physical network. Network virtualization presents logical networking devices and services—logical ports, switches, routers, firewalls, load balancers, VPNs and more—to connected workloads. Virtual networks offer the same features and guarantees of a physical network with the operational benefits and hardware independence of virtualization