A virtual private network (VPN) extends a private network across a public network and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. The benefits of a VPN include increases in functionality, security, and management of the private network.

<networking, security> (VPN) The use of encryption in the lower protocol layers to provide a secure connection through an otherwise insecure network, typically the Internet. VPNs are generally cheaper than real private networks using private lines but rely on having the same encryption system at both ends. The encryption may be performed by firewall software or possibly by routers. Link-level (layer 2 and 3) encryption provides extra protection by encrypting all of each datagram except the link-level information. This prevents a listener from obtaining information about network structure. While link-level encryption prevents traffic analysis (a form of attack), it must encrypt/decrypt on every hop and every path. Protocol-level encryption (layer 3 and 4) encryption encrypts protocol data but leaves protocol and link headers clear. While protocol-level encryption requires you to encrypt/decrypt data only once, and it encrypts/decrypts only those sessions that need it, headers are sent as clear text, allowing traffic analysis. Application (layer 5 up) encryption is based on a particular application and requires that the application be modified to incorporate encryption. {Cisco (http://cisco.com/univercd/cc/td/doc/product/lan/cat5000/cnfg_nts/rsm/rsm_pa/4801encr.htm)}. (1999-11-15)

Virtual Private Data Network

Virtual Private Network

Virtual Private Network

A mobile virtual private network (mobile VPN or mVPN) is a VPN which is capable of persisting during sessions across changes in physical connectivity, point of network attachment, and IP address.Phifer, Lisa.

A virtual private network (VPN) service provides a proxy server to help users bypass Internet censorship such as geoblocking and users who want to protect their communications against data profiling or MitM attacks on hostile networks.

A virtual network operator (VNO) or mobile virtual network operator (MVNO) is a provider of management services and a reseller of network services from other telecommunications suppliers that does not own the telecommunication infrastructure. These network providers are categorized as virtual because they provide network services to customers without owning the underlying network.

<networking> Software defined groups of host on a {local area network} (LAN) that communicate as if they were on the same wire, even though they are physically on different {LAN segments} throughout a site. To define a virtual LAN, the network administrator uses a virtual LAN management utility to establish membersip rules that determine which hostss are in a specific virtual LAN. Many models may exist but two seem to dominate: (1) Vitual Segment (or Port-Group) Virtual LAN. These are switched at the data link layer (OSI layer 2). Virtual segments turn an arbitrary number of physical segments into a single virtual segment that funtions as a self-contained traffic domain. (2) Virtual Subnet Virtual LAN: These are switched at the Network Layer (OSI layer 3). Subnet-oriented virtual LANs are based on subnet addresses used by IP, IPX, and other network layer protocols to normally identify physical networks. Administrators assign one subnet address to a number of switch ports (which may be on different switches and over a backbone). Once identified as a virtual subnet, the selected LANs function as a bridge group - traffic is bridged at Layer 2 within the virtual subnet and routed at Layer 3 between virtual subnets. ["The many faces of virtual LANs", Steven King, Network World, 1994/5?]. (1995-04-03)