Specifications

TOKEN RING OVERVIEW
2-32
Figure 2-9. MAC LLID Field Format
The Major Vector consists of a MAC length and ID (LLID) and 0, 1, or
more MAC sub-vectors.
The Major Vector Length (LL) is a 2-byte field that gives the length, in
bytes, of this specific MAC major vector, including the LL field itself.
The Major Vector ID (MVID) is a 2-byte field that identifies the function
that this major vector is to perform. The Major Vector ID is divided into
two subfields, Function Class and Command. The Command subfield is a
single byte that uniquely identifies the type of MAC frame.
The Function Class subfield is further divided into two 4-bit fields that
define the destination and source function classes for the MAC frame.
The destination and source fields provide two functions:
1. Provide a way to route a received MAC frame to the desired handling
function.
2. Provide a way to filter MAC frames that are built and sent by an
attached product, using the source class field. They also provide a way
to filter MAC frames received from the ring.
MAC
LLID
MAC
Subvector
MAC
Subvector
MAC
Subvector
4 bytes Variable
Length
Variable
Length
Variable
Length
MAC INFORMATION FIELD
Major Vector Length (LL)
Class Byte
Command Byte
Major Vector ID (MVID)
2 bytes
1/2
byte
1/2
byte
1 byte
Dest.
Class
Source
Class
Specific
Code Point