Token Ring Protocol Overview

Token Ring is a network technology where data is transmitted around a closed loop.

The Data Link Layer (DLL) of the OSI model handles the transmission of data between devices on the network.

A token is a special 3-byte frame that travels around the token ring, granting permission to transmit data to the station that possesses it.

Instead of broadcasting data, a station wanting to send data must first capture the token, insert its message and the destination address, and then send it around the ring.

Every station examines the passing data frame. The station with the matching destination address copies the data and changes the token back to a 0.

The originating station removes the message from the frame, and the empty frame continues to circulate, waiting to be used by another station.

An Active Monitor is a special station that monitors for problems like multiple tokens or missing tokens, fixing them by adding or removing tokens as needed.

A 4 Mbit/s Token Ring network can only have one token circulating at a time, whereas a 16 Mbit/s Token Ring can support multiple tokens.

A one-byte field within a Token Ring frame that indicates the type of data it carries. It specifies whether the frame contains regular data or control information.

The Frame Control field distinguishes between data frames, which carry user information, and control frames, which manage the network. Data frames (01) use the IEEE 802.2 protocol, while control frames (00) handle network housekeeping.

This field contains various bits that are involved in managing and controlling the token ring network. For example, the token bit indicates if this is a token frame, while the monitor bit is marked by the Active Monitor station when it sees the frame.

A six-byte field that identifies the recipient of the data within the frame. It indicates where the data should be sent within the network.

Another six-byte field that identifies the sender of the data within the frame.

A variable-length field that carries the core information transmitted over the network, ranging from 0 to 4500 bytes, depending on factors like the ring speed and type of data being sent.

A four-byte field that carries a Cyclic Redundancy Check (CRC) calculated for the frame. It ensures the data is transmitted without corruption.

A one-byte field at the end of the frame that provides a basic acknowledgment mechanism. It's used by the destination station to confirm it received and copied the data.

Token Ring allows stations with urgent data to prioritize their transmission by adjusting the token's priority level. The station can set the priority bits to its desired level (0-7) if the current token's priority is lower or equal to its request. The station does not immediately transmit; it waits for the token to circulate back.

A token is a 3-byte frame containing a start delimiter, access control byte, and end delimiter. It indicates the availability of the network for transmission.

A data frame in Token Ring is an expanded version of the token. It carries MAC management frames or data from upper layer protocols and applications. It includes additional fields like destination address, source address, and data payload.

A special bit pattern used for frame boundary identification. The bits are J,K,0,J,K,0,0,0, where J and K are code violations that ensure the hardware can detect the frame's start and end.

This 8-bit field contains control information for the token. It specifies things like the token's priority and indicates if it's a token or a data/command frame.

The data frame format in Token Ring includes: Starting Delimiter, Access Control, Frame Control, Destination & Source Addresses, PDU from LLC (IEEE 802.2), CRC, Ending Delimiter, and Frame Status.

This bit pattern marks the end of a frame, ensuring the network can recognize the end of a message.

Different frame types exist in Token Ring for managing MAC access and carrying data. Tokens are short frames for signaling, while data/command frames carry actual data and control information.

This frame is sent by a station intending to abort transmission. It has a start delimiter and end delimiter, but no data.

A special frame that circulates around the ring, granting permission to transmit data to the station that possesses it.

The process of selecting an Active Monitor in a Token Ring network when there's a problem with the existing one.

A station in a Token Ring network responsible for monitoring and maintaining the ring's health.

A station in a Token Ring network that can become an Active Monitor if needed.

A value assigned to each station in a Token Ring network to identify it, used in the Monitor Contention Process to determine the winner.

A function performed by the Active Monitor to ensure the token keeps circulating on the ring.

The Active Monitor ensures enough delay is added to the ring for the token to circulate.