FCS (4 bytes) (Token-Ring)

Protocol: Token-Ring MAC Token-Ring PCI

Field: frame check sequence (FCS)

Length: 4 bytes

Contents: checksum.

Token-Ring's checksum is not placed to fhe frame's end because both ending delimirer (ED) and frame status (FS) field contents may be changed by any ring station while passing the ring. If FCS was the last PDU field, the checksum would have to be calculated by every ring station again. This would cause less performance.