Which of the following is a computer network that is layered on top of an underlying computer network?

A.
WLAN

B.
RSN

C.
VPN

D.
TSN

Explanation:
A virtual private network (VPN) is a computer network that is layered on top of an underlying computer network. The private nature of a VPN means that the data traveling over the VPN is not generally visible to, or is encapsulated from, the underlying network traffic. The connectivity of a VPN is shown in the following figure. Similarly, the traffic within the VPN appears to the underlying network as just another traffic stream to be passed. A VPN connection can be envisioned as a pipe within a pipe, with the outer pipe being the underlying network connection. The term VPN can be used to describe many different network configurations and protocols.

Answer B is incorrect. Robust Security Network (RSN) is a protocol for establishing secure communications between wireless clients and wireless access points (WAPs). It is a part of the 802.11i standard. The RSN protocol functions are as follows. The wireless client sends a probe request frame.

As a response, the wireless access point (WAP) sends a probe response frame with an RSN information exchange (IE) frame. Now, the wireless client requests forauthentication and sends an association request frame. As a response, the wireless access point (WAP) sends an association response frame.

Answer D is incorrect. The transition Security Network (TSN) is an element of 802.11i authentication and encryption algorithms. It is an intermediate network similar to RSN that supports legacy security such as WEP within the BSS. It uses transition security network protocol that is used to authenticate clients in a most secure way.

Answer A is incorrect. Wireless Local Area Network (WLAN) is a network that enables devices to connect to the network wirelessly. WLAN uses radiated energy, commonly called high-frequency radio waves, to communicate among nodes.
IEEE defines standards for WLAN through 802.11 family.