Tunnel Mode

A mode of IPSec when used in a VPN. In transport mode, the IP packet data is encrypted but the header of the packet is not. An IPSec protocol used with ESP or Alt in which the ESP or Alt header is inserted between the IP header and the upperlayer protocol of an IP packet.
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A protocol in development by the IETF to support secure data exchange. Once completed, IPSec is expected to be widely deployed to implement virtual private networks (VPNs). IPSec supports two encryption modes: Transport and Tunnel. Transport mode encrypts the data portion (payload) of each packet but leaves the header untouched. Tunnel mode is more secure because it encrypts both the header and the payload. On the receiving side, an IPSeccompliant device decrypts each packet.
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A collection of procedures and data objects that is protected in a domain of its own so that the internal structure of a data object is accessible only to the procedures of the encapsulated subsystem and that those procedures may be called only at designated domain entry points. Encapsulated subsystem, protected subsystem and protected mechanisms of the TCB are terms that may be used interchangeably.
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An encryption technique that protects entire communications circuits by creating a secure tunnel between two points. This is done by using either a hardware or software solution that encrypts all traffic entering one end of the tunnel and decrypts all traffic exiting the other end of the tunnel. Encryption of information between nodes of a communications system. The application of online cryptooperations to a link of a communications system so that all information passing over the link is encrypted in its entirety.
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A network connection established between two systems over an existing private or public network. A VPN provides confidentiality and integrity for network traffic through the use of encryption. A secure private network that uses the public telecommunications infrastructure to transmit data. In contrast to a much more expensive system of owned or leased lines that can only be used by one company, VPNs are used by enterprises for both extranets and wide are intranets. Using encryption and authentication, a VPN encrypts all data that passes between two Internet points, maintaining privacy and security. Protected information system link utilizing tunneling, security controls (. See information assurance), and endpoint address translation giving the impression of a dedicated line.
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