electronic signaling specifications, and data-link, transport, and application layer protocols. For the purposes of simplicity, let’s just agree that a “network” is a collection of devices that can communicate in some fashion, and can successfully transmit and receive data amongst themselves. The term “private” is fairly straightforward, and is intricately related to the concept of “virtualization” insofar as VPN’s are concerned, as we’ll discuss in a moment. In the simplest of definitions, “private” means that communications between two (or more) devices is, in some fashion, secret – that the devices which are not participating in the “private” nature of communications are not privy to the communicated content, and that they are indeed completely unaware of the private relationship altogether. Accordingly, data privacy and security (data integrity) are also important aspects of a VPN which need to taken into consideration when considering any particular VPN implementation.

Another means of expressing this definition of "private" is through its antonym, "public." A “public” facility is one which is openly accessible, and is managed within the terms and constraints of a common public resource, often via a public administrative entity. By contrast, a “private” facility is one where access is restricted to a defined set of entities, and third parties cannot gain access. Typically, the private resource is managed by the entities who have exclusive right of access. Examples of this type of private network can be found in any organizational network which is not connected to the Internet, or to any other external organizational network, for that matter. These networks are private due to the fact that there is no external connectivity, and thus no external network communications.