Token Ring

Token Ring is a type of computer network where the devices are connected in a circular fashion. In this setup, each device is connected to two other devices, forming a ring. Data travels around this ring in one direction, and only one device can send data at a time. This is controlled by a small data packet called a "token."

The token is a special kind of data that circulates around the network. When a device wants to send information, it waits for the token to arrive. Once it gets the token, it attaches the data it wants to send along with the destination address and then releases the token back into the network. The token, now carrying the data, moves around the ring until it reaches the intended recipient, which then takes the data and releases the token back into the network, empty and ready for the next device to use.

Because only one device can hold the token and send data at any given moment, Token Ring networks are very orderly. This setup helps to prevent data collisions, which are common in other types of networks where multiple devices can send data at the same time. This makes Token Ring networks reliable and predictable.

A typical Token Ring network can operate at speeds of 4 or 16 megabits per second (Mbps). Devices are usually connected using special cables called shielded twisted-pair (STP) cables or fiber optics. The network can support a maximum of 72 devices connected in a ring.

One unique feature of Token Ring is that it uses a "monitoring" system to maintain the network's health. A special device, usually the first device that was powered on, becomes the "active monitor" that ensures the token is circulating properly. If problems are detected, the active monitor takes corrective actions, like regenerating a lost token.

Although once popular in the 1980s and early 1990s, Token Ring has largely been replaced by faster and more flexible technologies like Ethernet. However, understanding Token Ring is still useful for grasping the evolution and foundational concepts of computer networking.