A ring topology connects devices in a circular path. Data packets, often in the form of a token, are transmitted from one device to the next in a single, predetermined direction around the ring. Each node in the network acts as a repeater, receiving the data from the previous node and retransmitting it to the next. This process continues until the data reaches its intended destination. The defining characteristics are the closed loop and the unidirectional data flow that passes through each intermediary device.

B. Tree topology: This is a hierarchical structure combining star and bus characteristics. Data does not travel in a single-direction loop through every device.
C. Star topology: All devices connect to a central hub or switch. Data is sent to the central point and then forwarded, not passed sequentially through each device in a loop.
D. Mesh topology: This topology provides multiple, often redundant, paths between nodes. Data does not follow a fixed, single-direction loop through all devices.

1. Tanenbaum, A. S., & Wetherall, D. J. (2011). Computer Networks (5th ed.). Prentice Hall. In Chapter 4, Section 4.1.1, "The Medium Access Control Sublayer," the text describes the operation of a classic ring network (like the 802.5 token ring) where a token circulates around the ring, and stations must wait for it to pass by to transmit. This inherently describes a unidirectional, looped data path.

2. Stallings, W. (2016). Foundations of Modern Networking: SDN, NFV, and Cloud Computing. Addison-Wesley Professional. Chapter 2, "Requirements and Technology," discusses various LAN topologies. The section on Ring Topology (p. 43) explicitly states, "the network consists of a set of repeaters joined by point-to-point links in a closed loop... data are transmitted in one direction."

3. University of Pittsburgh, School of Computing and Information. (n.d.). Network Topologies. Courseware for INFSCI 0012: Introduction to Computer Networks. Retrieved from people.pitt.edu/~jmisite/course/infsci0012/notes/02-topologies.pdf. Page 10 describes the Ring Topology: "A number of repeaters are joined by point-to-point links in a closed loop... data are transmitted in one direction (unidirectional)."