BASIC TOKEN RING NETWORKS
Page A-3
3.
The frame addressed for yyy circulates around the ring. All
stations in the ring examine the frame, checking the address, in
successive order. When the transmission gets to yyy, station yyy
copies the data as it goes past.
4.
When the original transmission finishes the trip around the ring
and is seen by station xxx again, station xxx removes the
transmission from the ring. At this time, if station xxx has no
more data to send or if its Token Holding Time (THT) has
expired, station xxx releases the token back onto the ring.
5.
The ring is now available for use by another station. The token
resumes its circulation until it reaches the next station that is
waiting to send data. Here, the process will begin again with
that station seizing the token.
Unless an error occurs that disrupts normal token passing, the
original token remains in circulation. Lost tokens are detected by the
AM and appropriate corrective procedures are initiated.
Figure A-2. Token Ring Frame Formats
AC
SD
ED
SD - Starting Delimiter (1 octet)
AC - Access Control (1 octet)
FC - Frame Control (1 octet)
DA - Destination Address (2 or 6 octets)
SA - Source Address (2 or 6 octets)
INFO - Information (0 or more octets)
FCS - Frame Check Sequence (4 octets)
ED - Ending Delimiter (1 octet)
FS - Frame Status (1 octet)
AC
SD
ED
TOKEN FRAME
INFORMATION FRAME
DA
FC
SA
FS
INFO
FCS