Tunneling

• Tunneling is a protocol that permits the secure movement of information between two different networks.
• In simple words, Tunneling permits new network technologies to be implemented by using the existing network infrastructure.
• Tunneling permits private network communications to be sent across a public network, like the Internet, by a process called Encapsulation.
• The encapsulation process permits data packets to appear as though they are of a public nature to a public network when they are actually private data packets, allowing them to pass through unrecognized.
• Tunneling is also recognized in the terms of Port Forwarding.

Classical Scenario of Tunneling

• In computer networks, Tunneling protocols permit a network user to access or provide a network service that the underlying network does not support.
• The major use of a Tunneling protocol is to permit a foreign protocol to access or provide a network service that does not support that particular protocol.
• Example, Running IPv6 over IPv4.

Process of Tunneling

• The basic principle of tunneling is shown in Figure to deliver IPvY packets across the IPvX network in the middle, to achieve this deploy two tunnel endpoints on the border of the IPvX network.
• When Tunnel endpoint 1 receives an IPvY packet from the IPvY network, it encapsulates the IPvY packet with IPvX protocol header and puts the whole IPvY packet into the payload of the new IPvX packet.
• Then the IPvX packet is forwarded through the IPvX network.
• When Tunnel endpoint 2 receives the encapsulated IPvX packet, it decapsulates the packet, extracts the original IPvY packet, and forwards it to the IPvY network.
• In tunneling, the information is cut into smaller chunks called packets as they move along the tunnel for transportation.
• As the packets move through the tunnel, they are encrypted along with the process of encapsulation.
• Encapsulation allows the packets to arrive at their proper destination.
• At the final destination, decapsulation and decryption performed.

Various Protocols are used to perform tunneling, such as:

Point-to-Point Tunnelling Protocol (PPTP)

• Protects confidential information in public networks.
• Authorized users can access a private network.

Layer Two Tunnelling Protocol (L2TP)

• It is a combination of PPTP and Layer 2 Forwarding.
• Useful in the corporate field.
• Provide security mechanisms like encryption.

Other protocols like IPsec (GPRS tunneling protocol), and SSH (Secure Socket Tunneling Protocol) are also used in tunneling for particular tunneling work.