Token Passing - Token Ring (IEEE 802.5)
- Needs that station take turns sending data
- Token passing coordinates process
- Token is a especially formatted three-byte frame that circulates station wishing to transmit must first have possession
- Token passes from NIC to NIC in sequence if station has data to send and station takes token and sends data frame if not passes to neighbour
- Every station receives the frame one by one and examines the destination address
- If it matches frame is copied station checks the frame for errors changes bits to indicate the frame was received and copied
- Packet continues around the ring also is passed back to originating station
- Once the sender receives the frame in addition to recognizes its address in the sender field it examines the address-recognized bits
- If they are set it recognizes the frame was received and copied
- Sender subsequently discards the frame and releases the token back to the ring