What is the primary purpose of tunneling in internetworking?

Concept

A network tunnel creates a logical point-to-point link by encapsulating an original packet inside a packet of another protocol. The outer protocol carries the packet across an intermediate network, and the tunnel endpoint removes the outer header.

Application

Here, the two endpoint networks use the same inner networking protocol, while the intermediate network uses a different protocol or infrastructure. Encapsulation lets that intermediate network transport the original packets without needing to interpret their inner protocol, so the tunnel connects the two similar networks across the dissimilar network.

Contrast

• Encrypting data protects confidentiality; it is an optional security property of some tunnels, not the defining purpose of tunneling.

• Increasing WAN bandwidth changes link capacity; encapsulation instead adds a header and usually adds a small overhead.

• Preventing unauthorized access is an access-control or link-security function; tunneling by itself does not authorize users or devices.

• Connecting similar networks through a dissimilar intermediate network describes the logical link created by encapsulation and decapsulation.

Cross-check

RFC 2473 defines a tunnel as a virtual link between endpoints: one endpoint encapsulates the original packet and the other decapsulates it. That mechanism directly matches connecting compatible endpoint networks across a different transit network.

Therefore, the primary purpose is to connect two similar networks through a dissimilar intermediate network.