virtual private network

[¦vər·chə·wəl ‚prī·vət ′net‚wərk] (communications) A wide-area network whose links are provided by a common carrier although they appear to the users to behave like dedicated lines, and whose computers use a common cryptographic key to send messages from one computer in the network to another. Abbreviated VPN.

Virtual Private Network

(networking, security)(VPN) The use of encryption in thelower protocol layers to provide a secure connection throughan otherwise insecure network, typically the Internet. VPNsare generally cheaper than real private networks using privatelines but rely on having the same encryption system at bothends. The encryption may be performed by firewall softwareor possibly by routers.

Link-level (layer 2 and 3) encryption provides extraprotection by encrypting all of each datagram except thelink-level information. This prevents a listener fromobtaining information about network structure. Whilelink-level encryption prevents traffic analysis (a form ofattack), it must encrypt/decrypt on every hop and everypath.

Protocol-level encryption (layer 3 and 4) encryption encryptsprotocol data but leaves protocol and link headers clear.While protocol-level encryption requires you toencrypt/decrypt data only once, and it encrypts/decrypts onlythose sessions that need it, headers are sent as clear text,allowing traffic analysis.

Application (layer 5 up) encryption is based on a particularapplication and requires that the application be modified toincorporate encryption.

Cisco.

virtual private network

A private network configured within a public network such as the Internet or a carrier's network. Years ago, virtual private networks (VPNs) obsoleted private lines between company branches. Using data encryption to maintain privacy, VPNs also allow mobile users access to the company LAN.

In the past, common carriers used their vast networks to "tunnel" traffic between customer locations to give the appearance of a private network while sharing backbone trunks, no different than the way the Internet works. Prior to the Internet's IP protocol, VPNs were built over X.25, Switched 56, frame relay and ATM technologies. See PVC, SVC, computer security and information security.

Internet VPNs
Internet VPNs are very popular, and several security protocols are used. IPsec, L2TP and PPTP provide secure tunnels over the Internet. For brief transactions at a website, SSL is widely used. See IPsec, L2TP, PPTP and SSL.

Virtual IP VPNs from Carriers
A "virtual private routed network" (VPRN) connects the customer's IP router to the provider's IP router. See MPLS.

Ethernet VPNs from Carriers
Carriers encapsulate Ethernet frames in one location and deliver them to another. Connecting two Ethernets is a "LAN interconnect service," while multipoint connectivity is a "transparent LAN service" (TLS). A "virtual private LAN service" (VPLS) is a multipoint VPN using an IP/MPLS core to route traffic. See TLS, VPLS and IP/MPLS core.

Frame Relay VPNs from Carriers
Carriers have offered frame relay point-to-point and multipoint VPNs, whereby the customer's equipment converts internal IP packets to frame relay packets. Adding a location in such a network means provisioning virtual circuits from the new site to all the other sites. See frame relay.

单词	virtual private network
释义	DictionarySeeVPN virtual private network virtual private network [¦vər·chə·wəl ‚prī·vət ′net‚wərk] (communications) A wide-area network whose links are provided by a common carrier although they appear to the users to behave like dedicated lines, and whose computers use a common cryptographic key to send messages from one computer in the network to another. Abbreviated VPN. Virtual Private Network (networking, security)(VPN) The use of encryption in thelower protocol layers to provide a secure connection throughan otherwise insecure network, typically the Internet. VPNsare generally cheaper than real private networks using privatelines but rely on having the same encryption system at bothends. The encryption may be performed by firewall softwareor possibly by routers. Link-level (layer 2 and 3) encryption provides extraprotection by encrypting all of each datagram except thelink-level information. This prevents a listener fromobtaining information about network structure. Whilelink-level encryption prevents traffic analysis (a form ofattack), it must encrypt/decrypt on every hop and everypath. Protocol-level encryption (layer 3 and 4) encryption encryptsprotocol data but leaves protocol and link headers clear.While protocol-level encryption requires you toencrypt/decrypt data only once, and it encrypts/decrypts onlythose sessions that need it, headers are sent as clear text,allowing traffic analysis. Application (layer 5 up) encryption is based on a particularapplication and requires that the application be modified toincorporate encryption. Cisco. virtual private network A private network configured within a public network such as the Internet or a carrier's network. Years ago, virtual private networks (VPNs) obsoleted private lines between company branches. Using data encryption to maintain privacy, VPNs also allow mobile users access to the company LAN. In the past, common carriers used their vast networks to "tunnel" traffic between customer locations to give the appearance of a private network while sharing backbone trunks, no different than the way the Internet works. Prior to the Internet's IP protocol, VPNs were built over X.25, Switched 56, frame relay and ATM technologies. See PVC, SVC, computer security and information security. Internet VPNs Internet VPNs are very popular, and several security protocols are used. IPsec, L2TP and PPTP provide secure tunnels over the Internet. For brief transactions at a website, SSL is widely used. See IPsec, L2TP, PPTP and SSL. Virtual IP VPNs from Carriers A "virtual private routed network" (VPRN) connects the customer's IP router to the provider's IP router. See MPLS. Ethernet VPNs from Carriers Carriers encapsulate Ethernet frames in one location and deliver them to another. Connecting two Ethernets is a "LAN interconnect service," while multipoint connectivity is a "transparent LAN service" (TLS). A "virtual private LAN service" (VPLS) is a multipoint VPN using an IP/MPLS core to route traffic. See TLS, VPLS and IP/MPLS core. Frame Relay VPNs from Carriers Carriers have offered frame relay point-to-point and multipoint VPNs, whereby the customer's equipment converts internal IP packets to frame relay packets. Adding a location in such a network means provisioning virtual circuits from the new site to all the other sites. See frame relay. MedicalSeePVC Virtual Private Network Virtual Private Network Also called a VPN. A computer network connecting the main office of a company to its regional offices, and sometimes to individuals using the network remotely. Until the 1990s, a VPN was a dial-up connection or a network set up especially for the company. Since then, most VPNs simply use the Internet. See VPN See VPN
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