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Station Management (SMT) is the layer of the FDDI protocol that is responsible for monitoring network operation, detecting errors, and isolating faults. SMT initializes nodes, inserts nodes into the ring, and removes nodes from the ring.
Each FDDI node participates in ring management by exchanging SMT information (using SMT frames) with other nodes on the ring. There are different types of SMT frames, each used for a specific purpose. For example, SMT status report frames are sent wherever a change occurs in the ring configuration. Similarly, SMT neighbor information frames (SMT NIFs) are used by FDDI nodes to determine or announce their neighbors. These SMT NIFs contain the address of the sender, the address of its nearest upstream neighbor, and additional information about the node itself.
By capturing and analyzing these frames, Ring Monitor can build a map of the ring. You use Ring Monitor to configure, display, and print FDDI statistics.
Ring Monitor builds a ring map by collecting SMT NIFs. These SMT frames are exchanged periodically, at intervals of 2 to 30 seconds. When the FDDI ring monitor application is launched, the FDDI NSP starts collecting the SMT NIFs and building the FDDI ring map.
The ring map is complete only when the probe has collected SMT NIFs from all the nodes on the ring. Until that happens, a partial ring map is displayed and the Ring Map Status in the Ring Monitor is displayed as "Incomplete." When the ring map is complete (typically, 10 to 60 seconds), the Ring Map Status is displayed as "Complete." The ring map is rebuilt whenever a change occurs in the ring configuration.
Although the time it takes to build the ring map is typically less than 60 seconds, under certain conditions, the ring map may take longer to complete, or may never complete. If the ring is overloaded, the nodes take longer (several minutes) to exchange SMT-NIFs, and the time to build the ring map increases as well. If there is a node on the ring that has stopped or a node that does not exchange SMT-NIFs, the ring map will never be completed. This happens if the node has hung, is too busy to participate in the SMT-Neighbor Protocol, or if it does not conform to the SMT-NIF protocol.
This section describes the procedures you use to monitor your FDDI network with Ring Monitor.
To launch Ring Monitor from the TrafficDirector main window and display the Ring Monitor Ring Station List for the FDDI agent you select, take the following steps:
Step 1 Launch Ring Monitor for an FDDI or CDDI type agent if you have not already done so. See "Launching Ring Monitor" in Chapter 20, "Ring Monitor."
The TrafficDirector Ring Station List window for the selected agent opens (Figure 21-1). From this window, you can work with Ring Monitor in a variety of ways.
The Ring Station List window upper list box shows information about each node on the ring, and contains the following information:
| Ring Order | The order of this station in the ring. |
| Station | The name of the station. |
| Address | The address of the station. |
| Last Enter Time | The last time the station entered the ring. |
| Last Exit Time | The last time the station exited the ring. |
| RIns | The number of times a station has been inserted into the ring. |
| Status | Whether a station is active (currently in the ring) or inactive (not currently in the ring). |
To view data on active stations, select View>Active Stations Only.
You can change the way TrafficDirector sorts the information provided in the window list box by selecting Sort, then selecting a variable listed in Table 21-1.
| Variable | Sorts by |
|---|---|
| Ring Order | The position of the station in the ring. This is the default sort order when you first launch Ring Monitor. |
| MAC Order | MAC addresses, sorted in descending order. |
| Enter Time | The last time the station entered the ring, sorted in descending order. |
| Exit Time | The last time the station exited the ring, sorted in descending order. |
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