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Troubleshooting

Some General Guidelines For Token-Ring Troubleshooting

Things To Look For On The Ring

When examining an 802.5 Token-Ring network the first task is to establish that the ring maintenance operations are working properly. Some guidelines include:

• The Ring-Poll/Neighbor Notification process should start every 7 seconds with the transmission of an Active Monitor Present frame.
  • Range: 6.996 - 7.012 is typical, acceptable, and normal
• Standby Monitor Present frames should be transmitted every 20 ms after the start of Ring-Poll
  • Range: 15 - 25 ms is typical, acceptable, and normal (.015-.025 seconds)
• Ring purge frames should only be associated with station insertion or removal. Other Ring Purge frames indicate that the token has been corrupted due to something other than a normal insertion or removal.
  • Range: Non-insertion/removal related ring purges: no more than one per minute or one per megabyte of user traffic on the ring.
• Soft Error Report frames should only be associated with station insertion and removal. The act of inserting or removing may cause Burst, Line, Lost Frame, or Token errors. Rarely an Abort Delimiter may be sent. Insertion and removal do not cause any other soft errors. The Soft Error Report frame is sent 2 seconds after the first error was detected.
  • Range: The Soft Error Report may be observed anywhere from 1.8 seconds to 2.2 seconds after the event. The report of anything other than the indicated errors is indicative of a problem. Insertion and removal may not produce any errors. Any of the normal errors that do result may be ignored.

The First Steps In Your Troubleshooting Methodology

• Confirm normal MAC behavior during ring poll
  • AMP Every 7 Seconds
  • No Ring Purge frames (not associated with insertion or removal)
• No ‘abnormal’ Soft Error Reports

Analyzing A Beaconing Ring

• Look for the station that is beaconing the longest. Under 16 seconds might be an intermittent condition. Over 26 seconds is a solid beacon.
  • A Priority 4 (Streaming Signal, Claim Token) beacon is transient; "Move On!"
  • Signal Loss implies a cable break or hardware failure
  • Streaming Signal/Claim Token implies a cable too long or environmental noise.
    Note: There is no clean way to isolate a ring beaconing problem by simply looking at a protocol analyzer trace file. While some conditions may be self-evident the more common experience is that the trace file analysis simply contributes to the overall information needed to solve the problem. The trace file doesn’t usually tell the entire story. This is because you can only see the frames coming from your immediate upstream neighbor. You can’t see the overall interrelated state of all the stations on the ring.
  
  When evaluating a beaconing ring, keep in mind that you’ll want to watch for the station that is holding the Beacon on the ring for the longest time, since it’s possible to see several different devices beaconing at one time or another.
• Beacon Transmit Auto Removal Test
  • If a station continues to be in Beacon Transmit mode for 26 seconds, it goes into Beacon Transmit Auto Removal Test, meaning it removes itself from the ring and checks if it is the cause of the ring beaconing.
• Beacon Receive Auto Removal Test
  • If a station receives 8 consecutive Beacon frames where its address is listed as the upstream neighbor of the station beaconing, the station will perform a Beacon Receive Auto Removal Test by removing itself from the ring and checking if it is the cause of the ring beaconing.