Specifications

TOKEN RING OVERVIEW
2-30
Figure 2-7. Frame Control Field Format
Destination Address (DA)
The DA field shown in Figure 2-8 contains the address of the station or
stations for which that frame is intended. The DA field is further
subdivided as follows:
Bit 1
Individual or group address. If this bit is set to a ‘1’ then it is a group
address. If a ‘0’ then it is an individual address.
Bit 2
Universally or locally administered address. If this bit is set to a ‘1’ then
the address is locally administered. If it is set to ‘0’ then it is a universally
administered address. This is only true for 6-byte addressing as 2-byte
addressing can only be locally administered.
Bits 3 to 48
Ring/Station or Group Node Addresses. Within this 46-bit field there may
be a specific ring and station address or a Group Node Address with
control information known as functional addressing. These addresses
represent special functions that exist in a LAN environment, i.e., Active
Monitor. Functional addresses are associated with ring management
functions.
A Broadcast DA is a group address consisting of 16 or 48 ‘1s’ (2 or 6 octet
addresses) that constitute a broadcast address.
F F Z Z Z Z Z Z
Note that ‘r’ bits are reserved.
ZZZZZZ = Control Bits
Undefined
rrrYYY = PDU priority
rrrYYY = control value for
each of 25 MAC frames and
17 extended IBM MAC frames
FF = Frame Bits
1x = reserved
01 = Data Frame
00 = MAC Frame
with vector identifier
SD AC FC DA SA INFO FCS ED FS