Troubleshooting Egress Queue Bandwidth Impacted by Congestion
Problem
Description
Congestion on an egress port causes egress queues to receive less bandwidth than expected. Egress port congestion can impact the amount of bandwidth allocated to queues on the congested port and, in some cases, on ports that are not congested.
Cause
Egress queue congestion can cause the ingress port buffer to fill above a certain threshold and affect the flow to the queues on the egress port. One queue receives its configured bandwidth, but the other queues on the egress port are affected and do not receive their configured share of bandwidth.
Solution
The solution is to configure a drop profile to apply weighted random early detection (WRED) to the queue or queues on the congested ports.
Configure a drop profile on the queue that is receiving its configured bandwidth. This queue is preventing the other queues from receiving their expected bandwidth. The drop profile prevents the queue from affecting the other queues on the port.
To configure a WRED profile using the CLI:
Name the drop profile and set the drop start point, drop end point, minimum drop rate, and maximum drop rate for the drop profile:
[edit class-of-service] user@switch# set drop-profile drop-profile-name interpolate fill-level percentage fill-level percentage drop-probability 0 drop-probability percentage