Tunneling is a technique that enables remote access users to connect to a variety of network resources through a public data network.
Tunneling is a technique that enables remote access users to connect to a variety of network resources (Corporate Home Gateways or an Internet Service Provider) through a public data network.
By using Tunneling one can (for example) carry a payload over an incompatible delivery-network, or provide a secure path through an untrusted network.
Users can also use tunneling to "sneak through" a firewall, using a protocol that the firewall would normally block, but "wrapped" inside a protocol that the firewall does not block, such as HTTP. If the firewall policy does not specifically exclude this kind of "wrapping", this trick can function to get around the intended firewall policy.
Major tunneling protocols (ie: Layer 2 Tunneling Protocol (L2TP), Point to Point Tunneling Protocol (PPTP), and Layer 2 Forwarding (L2F)) encapsulate Layer 2 traffic from the remote user and send it across the public network to the far end of the tunnel where it is de-encapsulated and sent to its destination. The most significant benefit of Tunneling is that it allows for the creation of VPNs over public data networks to provide cost savings for both end users, who do not have to create dedicated networks, and for Service Providers, who can leverage their network investments across many VPN customers.
