What is Token Ring?

Token Ring is a network where computers are connected as if they were in a circle, and the network packet travels through the ring, allowing the computers to exchange information with each other.

What is Token Ring?

Token Ring Networking

The token ring was developed by IBM in the 1970s with logical ring topology and token passing access technique. Its first design was made in 1969 by E. E. Newhall. IBM first published the Token-Ring topology in March 1982.

Token-Ring network is defined in the IEEE 802.5 standard, but this document refers to the method of transmitting information rather than the method of connecting computers.

While continuing to develop this network, the maximum speed was increased to 4 Mbps in 1988 using twisted pair hardware. Later, the second generation Token Ring-II with speeds up to 16 Mbps was introduced using coaxial cable and fiber optics.

The cabling costs of the new local area networks to be created have become an important factor as the old networks with twisted pair wires with Token Ring-II had to be rewired.

Features

The token network has a logical ring network topology but is designed like a physical star network topology.

Unlike Ethernet networks, these networks are the determinant type of network. The main reason why the device is accessing the medium is controlled and only one computer can transmit data at a time. This control is done through data packets that determine which computer can transmit data.

In a Token Ring network, computers are connected in a star shape to central wiring hardware called MAU (Multistation Access Unit). Although this hardware connects computers together like a physical star topology, it logically works as a ring topology.

Also, Lobes are used to connect individual computers to the MAU device and the maximum cable length for one lobe is 22.5 or 100 meters. If the network is to be expanded, this length can be up to 2.5 km by using repeaters.

Token networks can be expanded through the Ring-Out and Ring-In ports of MAUs, but up to 33 devices can be connected to each other. Fiber cable can be used in larger networks such as campus.

This type of network also has an advanced priority system that prioritizes specific users to higher priority computers to use the network more frequently. An MAU device can be managed over the serial interface with the SNMP protocol.

Also, Token Ring and IEEE 802.5 are the first and basic examples of token transmission networks.

Cable Structure

The cable commonly used for data transmission in this network is either shielded or unshielded twisted pair. However, coaxial cable or fiber optic cable can be used to achieve higher data transfer rates.

If the cable used in this network breaks or gets damaged somewhere in the ring, a star wiring center that can automatically detect and correct wiring faults can be used to solve this problem.

Thus, a problem that may occur in the ring is repaired and the network continues to operate. Also, computers join the ring network via RIUs (Ring Interface Units).

How Does It Work?

Token networks use various mechanisms to detect errors in the network. One of these mechanisms is to choose a computer on the network as an active monitor.

This computer functions as a central source of time information for computers in another ring and performs the maintenance function.

The active monitoring computer could potentially be any computer on the network and its task is to eliminate the constant roaming of ring frames.

If this process fails when a packet is sent to a computer, other computers are blocked from forwarding their own frames and the network may be blocked. The active monitor detects these frames, extracts them from the ring network, and creates a new token.

Advantages

  1. It does not require routing.
  2. Wiring requirement is low.
  3. The network is easy to grow.
  4. It can send data to more stations by amplifying the signal.

Disadvantages

  1. It is highly sensitive to failures that may occur in the network.
  2. Due to a failure in the ring, the entire network is disabled.
  3. It is difficult as the software configurations of each node are more complex.

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