VPN, network that uses public wires or the Internet to connect between nodes (uses encryption and security measures to protect data and prevent unauthorized access)
A virtual private network (VPN) is a
communications network tunneled through another network, and dedicated for a specific network. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.
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<
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.
(1999-11-15)
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