52 SunFDDI/P1.0 Adapter User’s Guide—May 1997
6
Media Access Control(MAC) Layer
The Media Access Control layer specifies the access mechanism used to
transmit and receive data on the FDDI network. It packages digital data in
frames.
The MAC layer specifies three classes of digital data traffic:
•Synchronous (guaranteed) traffic
•Asynchronous (priority-based) traffic
•Restricted (dialogue-based) traffic
The MAC layer uses a timed token rotation protocol that regulates how much
digital data can be sent at one time. This protocol ensures that the network
bandwidth is used predictably and efficiently.It also gives the FDDI network
its distinctive “ring” topology.
The FDDI stations connected on the network use a token to control the right to
transmit data for a predefined time, determined by the local timed target
rotation timer (TTRT) on each station. When an FDDI station completes
transmission, it releases the token for use by downstreamstations. In this way,
the token rotates continuously around the ring.
Each attachment to an FDDI network is identified by a unique MAC address.
The first SunFDDI/P card installed in a machine takes its identity from the
host-resident MAC address that is stored in nonvolatile memory on the
motherboard of the machine in which it is installed. Each subsequent
SunFDDI/P SBus card takes its identity from the card-residentMAC address
stored in its own IDPROM.
Use the pf_macid(1M) utility to display the card-resident MAC address. See
Chapter 8, “Using the SunFDDI Network Utilities” for detailed instructions.
Station Management (SMT) Layer
The Station Management layer provides services to manage, control, and
configure the FDDI network. It is also referredto as the network management
layer.