What are the Token Ring Frame Formats in Computer Network?

There are three types of frame formats supported on a Token Ring network: token, abort, and data/command frame. The token format is the mechanism by which access to the ring is passed from one computer to another on the network.

The token format consists of three bytes, where the starting and ending delimiters indicate the beginning and end of a token frame. The middle byte is an access control byte that contains priority bits, reservation bits, a token bit, and a monitor bit.

Frame Format Components

The components of the Token Ring data/command frame format are as follows:

• Start Delimiter (SD) − A one-byte field that alerts the receiving station to the arrival of a frame and allows it to synchronize its retrieval timing.

• Access Control (AC) − A one-byte field containing four subfields: three priority bits, one token bit, one monitor bit, and three reservation bits.

• Frame Control (FC) − A one-byte field that indicates the type of information contained in the Protocol Data Unit (PDU) and distinguishes between data and control frames.

• Destination Address (DA) − A 2-6 byte field containing the physical address of the frame's destination. For inter-network communication, this is the router's address.

• Source Address (SA) − A 2-6 byte field containing the physical address of the sending station.

• Data − A variable-length field (up to 4500 bytes) containing the actual data or PDU being transmitted.

• Frame Check Sequence (FCS) − A 4-byte checksum field used for error detection, containing a cyclic redundancy check (CRC) value calculated from the frame contents.

• End Delimiter (ED) − A one-byte field that indicates the end of the frame's data and control information.

• Frame Status (FS) − A one-byte field set by the receiver to indicate frame processing status, such as whether the frame has been copied or recognized.

Frame Types

Conclusion

Token Ring networks use three distinct frame formats to manage network access and data transmission. The token frame provides orderly access control, while data/command frames carry the actual information with comprehensive addressing and error detection capabilities.