Transmit Queue Monitoring (7100-Series)

The transmit queue monitoring feature monitors ports for stalled buffers. 7100-Series firmware releases 7.91.03 and greater support transmit queue monitoring. When a port is congested, if a configured minimum number of packets are not transmitted within the sample interval set in seconds, the transmit buffer is considered to be in a stalled state. The stalled buffer condition can occur for reasons such as duplex misconfiguration or the continuous reception of pause frames that prevent the port from transmitting. If no intervention takes place, it is possible for all packet buffers to stall preventing any new traffic from being received or forwarded.

When transmit queue monitoring detects a stalled buffer, a set of three independently configured actions will occur if a configured error threshold of sample intervals for each action is met:

• The logging threshold generates a Syslog message notification that the condition exists
• The ignore pause threshold disables processing of received pause packets on the port
• The shutdown port threshold disables the port
  

  Note

  Setting the disable port threshold to trigger before the ignore pause frames or logging thresholds causes these action thresholds to never be met and the action will not occur.

The ignore pause and disable port thresholds support a configured hold time. The hold time is the amount of time the port will remain in the ignore pause or disabled port state. Once the hold time expires, the port returns to the normal state and continues to monitor the stalled condition. If the hold time is set to 0, the port will not return to the normal state until you administratively clear the condition.

The transmit queue monitoring feature is enabled by default and can be disabled or re-enabled using the set txqmonitor state command.

The sample interval, during which a configured minimum number of packets must be transmitted by the port buffer to avoid being set to the buffer stalled state, can be configured in seconds using the set txqmonitor sampleinterval command. The sample interval defaults to 1 second.

The minimum number of packets that must be transmitted by the transmit buffer to avoid being set to the buffer stalled state can be configured using the set txqmonitor minrate command. The minimum number of packets transmitted by the transmit buffer defaults to 1 packet.

The action thresholds in number of consecutive errored sample intervals for logging, ignoring pause frames, and disabling the port can be configured using the set txqmonitor threshold command. The logging threshold is 2 consecutive errored sample intervals. The ignore pause frames threshold is 5 consecutive errored sample intervals. The disable port threshold is 10 consecutive errored sample intervals.

The amount of time a port will be down if the disable port threshold action is triggered can be set using the set txqmonitor downtime command. The default period is set to 0 sample intervals. The port must be administratively cleared using the clear txqmonitor operstatus command.

The amount of time a port will ignore all pause frames it receives if the ignore pause action threshold is met can be configured using the set txqmonitor ignorepausetime command. The default period is set to 0 sample intervals. The ignore pause time must be administratively cleared using the clear txqmonitor operstatus command.

The generation of traps each time a transmit queue monitoring threshold is met can be enabled or disabled using the set txqmonitor trapstatus command. The generation of traps is enabled by default.