Specifications

2-31
TOKEN RING OVERVIEW
Figure 2-8. Destination Address Field
MAC Frame Format
MAC frames are originated, received, and acted upon by stations. These
frames control the operation of the Token Ring network and any station
operations that affect the ring. The MAC frames all have the same Frame
Control field format. The control bits for a MAC frame are contained in the
MA Information Field (also called MAC LLID Frame), shown in
Figure 2-9.
I/G U/L Ring# Station Address
I/G bit = 0 - Individual station address
I/G bit = 1 - Group node address
U/L bit = 0 - Universal addressing, 46 bits in each station’s MAC
PROM. ISO/IEEE administered
U/L bit = 1 - Local addressing, may be 46 or 15 bits
SD AC FC DA SA INFO FCS ED FS
All Broadcast, Group, and Functional
Addresses Require the Leftmost Address Bit = 1
FF FF FF FF FF FF Broadcast to all local stations
C0 00 FF FF FF FF Broadcast address, MAC frames
Functional Addresses Require Octet Three = 0XXXXXXX
C0 00 00 00 00 01 Active Monitor
C0 00 00 00 00 02 Ring Parameter Server
C0 00 00 00 00 08 Ring Error Monitor
C0 00 00 00 00 10 Configuration Report/Server/Net Mgr.
C0 00 00 00 01 00 Bridge
Group Addresses Require Octet Three = 1XXXXXXX
YY YY ZZ ZZ ZZ ZZ Group address supplied by app.
Where: Y = Group Root Address
Z = Specific Group Address