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Troubleshooting a Port Reset on QFabric Systems When a Queue Stops Transmitting Traffic

Problem

Description

In QFabric systems, if any queue that contains outgoing packets does not transmit packets for 12 consecutive seconds, the port automatically resets.

Cause

Failure of a queue to transmit packets for 12 consecutive seconds may be due to:

  • A strict-high priority queue consuming all of the port bandwidth

  • Several queues consuming all of the port bandwidth

  • Any queue or port receiving continuous priority-based flow control (PFC) or 802.3x Ethernet PAUSE messages (received PFC and PAUSE messages prevent a queue or a port, respectively, from transmitting packets because of network congestion)

  • Other conditions that prevent a queue from obtaining port bandwidth for 12 consecutive seconds

Solution

If the cause is a strict-high priority queue or other queues consuming all of the port bandwidth, you can use rate shaping to configure a maximum rate for the queues that are using all of the port bandwidth and preventing other queues from obtaining bandwidth on the port. You configure a maximum rate by creating a scheduler, using a scheduler map to apply it to a forwarding class (which maps to an output queue), and applying the scheduler map to the port using a forwarding class set and a traffic control profile.

To configure rate shaping using the CLI:

  1. Name the existing scheduler or create a scheduler and define the maximum bandwidth as a rate or as a percentage:

  2. Configure a scheduler map to associate the scheduler with the forwarding class (queue) that is consuming all of the port bandwidth:

  3. Associate the scheduler map with a traffic control profile:

  4. Associate the traffic control profile (and thus the scheduler map that contains the rate shaping queue scheduler) with a forwarding class set and apply them to the interface that is being reset:

For example, a strict-high priority queue is using all of the bandwidth on interface shpnode:xe-0/0/10 and preventing other queues from transmitting for 12 consecutive seconds. You decide to set a maximum rate of 7 Gbps on the strict-high priority queue to ensure that at least 3 Gbps of the port bandwidth is available to service other queues. Table 1 shows the topology for this example:

Table 1: Components of the Rate Shaping Troubleshooting Example

Component

Settings

Affected interface

shpnode:xe-0/0/10

Scheduler (strict-high priority scheduler)

Name: shp-sched

Shaping rate: 7g

Priority: strict-high

Note:

This example assumes that the scheduler already exists and has been configured as strict-high priority, but that rate shaping to prevent the strict-high priority traffic from using all of the port bandwidth has not been applied.

Scheduler map

Name: shp-map

Forwarding class to associate with the shp-sched scheduler: strict-high

Note:

This example assumes that a strict-high priority forwarding class has been configured and assigned the name strict-high.

Traffic control profile

Name: shp-tcp

Note:

This example does not describe how to define a complete traffic control profile.

Forwarding class set

Name: shp-pg

To configure the scheduler, map it to the strict-high priority forwarding class, and apply it to interface shpnode:xe-0/0/10 using the CLI:

  1. Specify the scheduler for the strict-high priority queue (shp-sched) with a maximum bandwidth of 7 Gbps:

  2. Configure a scheduler map (shp-map) that associates the scheduler (shp-sched) with the forwarding class (strict-high):

  3. Associate the scheduler map shp-map with a traffic control profile (shp-tcp):

  4. Associate the traffic control profile shp-tcp with a forwarding class set (shp-pg) and the affected interface (shpnode:xe-0/0/10):