A technology that enables one network to send its data via another network's connections. Tunneling works by encapsulating a network protocol within packets carried by the second network. For example, Microsoft's PPTP technology enables organizations to use the Internet to transmit data across a VPN. It does this by embedding its own network protocol within the TCP/IP packets carried by the Internet.

The path that is followed by a datagram while it is encapsulated.

A virtual pipe that connects two nodes (i.e. client computer and server) over a public network like the Internet. A tunnel is created by encapsulation and encryption of packets. Thereby, tunnel provides secure and private link across a public network. Physically, packets in a tunnel may take different routes in their travel to a destination node. Also see VPN.

The path followed by an IP packet when it is encapsulated in a second IP packet with an alternate IP destination addresses. While it is encapsulated, the internal datagram is protected from normal Internet routing. The decapsulating agent decapsulates the original datagram and so it can be delivered to the original destination address.

a logical entity

a logical interface on a Cisco router that provides a way to encapsulate passenger packets inside a transport protocol

a logical pathway thru the network

a logical structure that encapsulates the frame and data of one protocol inside the data field of another protocol

a method for sending datagrams between routers separated by gateways that do not support multicasting routing

a router where one interface uses a different protocol than the rest

The path established by one network to send its data via another network's connections; runs on OSI Layer 2 protocol such as TCP/IP, VPN and PPTP.

The logical path by which the encapsulated packets travel through the transit internetwork.

A path followed by a first packet while it is encapsulated within the payload portion of a second packet.

A very broad term which generally means that a data path has been created through a network, by encapsulating the original packets into some other protocol packets. Two popular examples for tunnelling are: hiding original packets (secure tunnels); providing a way of transferring non-supported packets, which are encapsulated within the network protocol packets, e.g. IP multicast through IP unicast-only network.

The path followed by a packet while it is encapsulated from the Home Agent to the mobile node. The model is that, while it is encapsulated, a packet is routed to a knowledgeable decapsulating agent, which decapsulates the datagram and then correctly delivers it to its ultimate destination.

Secure communication path between two peers, such as two routers.

In the context of this document, a tunnel refers to a secure communication path between two peers, such as two PIX Firewall units. It does not refer to using IPSec in tunnel mode.

A secure communication path between two peers, such as a client and a router.

The link between tunnel client and tunnel server where data is encrypted and encapsulated.

A secure communication path between two peers, such as routers.

A secured, private "path" connecting two points through a public network

A logical connection over which data is encapsulated. Typically, both encapsulation and encryption are performed and the tunnel is a private, secure link between a remote user or host and a private network. See also: encryption; host; tunnel server; voluntary tunnel

A virtual, direct pathway with which to transmit bidirectional traffic between two end points. See also VPN.

vb. To encapsulate or wrap a packet or a message from one protocol in the packet for another. The wrapped packet is then transmitted over a network via the protocol of the wrapper. This method of packet transmission is used to avoid protocol restrictions. See also communications protocol, packet (definition 2).

In Virtual Private Networks ( VPN), an encrypted connection between sites. Only the originator and the receiver of the message see it in its clear state. Any hacker trying to intercept the message en route gets nothing but a scrambled mess. Because the path of a VPN message has "light" (clear text) at each end but "darkness" (obscurity) at all the between-points, it is called, metaphorically, a VPN tunnel. On a technical level, a tunnel is a means of exchanging encapsulated data packets between two parties. Though some tunneling protocols forward cleartext packets, WatchGuard utilizes tunneling protocols such as PPTP and IPSec ESP that forward encrypted packets.

Private, secure path through an otherwise public network.

Tunnel is an often misused term. In one sense it can be used to refer to the Raptor Firewall's packet filtering ability - that is, local tunnels. It can also be used when discussing the implementation of VPN, as in RaptorMobile tunnels, IPSEC tunnels, or ISAKMP tunnels.