Customize Egress Port Link Quality Metrics for DLB

Dynamic load balancing (DLB) selects an optimal link based on the quality of the link so that traffic flows are evenly distributed across your network. You (the network administrator) can customize the way DLB assigns quality metrics of egress ports so that DLB selects the optimal link.

DLB assigns each egress port that is part of equal-cost multipath (ECMP) to a quality band. Quality bands are numbered from 0 through 7, where 0 is the lowest quality and 7 is the highest quality. DLB tracks two metrics on each of the ports, and it uses these metrics to compute the link quality:

• Port load metric: The amount of traffic recently transmitted over each ECMP link, measured in bytes.

• Port queue metric: The amount of traffic enqueued on each ECMP link for transmission, measured in number of cells.

Based on the member port load and queue size, DLB assigns one of the quality bands to the member port. The port-to-quality band mapping changes based on the instantaneous port load and queue size metrics.

By default, DLB weighs the port load metric and port queue metric equally when evaluating link quality. You can configure DLB to base the link quality more heavily on the port load than the port queue, or vice versa. Configure the amount of weight DLB places on the port load using the rate-weightage statement at the [edit forwarding-options enhanced-hash-key ecmp-dlb egress-quantization] hierarchy level. DLB assigns the remaining weight percentage to the port queue. For example, if you configure the rate-weightage value to be 80, DLB places 80% weight on the port load and 20% weight on the port queue when evaluating the quality of a link.

You can also configure port load thresholds that determine the upper and lower quality bands. The thresholds are percentages of the total port load that you configure using the min and max options. DLB assigns any egress port with a port load falling below this minimum to the highest quality band (7). Any port load larger than the maximum threshold falls into the lowest quality band (0). DLB divides the remaining port load quantities among quality bands 1 through 6.

For example, if you configure the minimum to be 10 and the maximum to be 70, DLB assigns any egress port with a port load that takes up less than 10 percent (%) of the total port load to quality band 7. DLB assigns any egress port with a port load taking up more than 70% of the total port load to quality band 0. DLB then assigns egress ports with port loads taking up 10% through 70% of the total port load to quality bands 1 through 6.

See Feature Explorer for platform and release support. Starting in Junos OS Evolved Release 23.4R2, this feature is supported on these platforms:

• QFX5230-64CD

• QFX5240-64OD

• QFX5240-64QD

Configure the egress port quality metric using the following options of the egress-quantization statement at the [edit forwarding-options enhanced-hash-key ecmp-dlb] hierarchy level:

• rate-weightage: How much weight DLB puts on the port load metric, or amount of traffic, when determining the link quality. The range is 0 through 100, where 100 means that DLB bases link quality 100% on the port load.

• min Minimum port load in percentage (1 through 100). DLB assigns any egress port with a port load falling below this minimum to the highest quality band (7).

• max Maximum port load in percentage (1 through 100). DLB assigns any egress port with a port load above this maximum to the lowest quality band (0).

When the rate weightage changes, the device repairs all ECMP DLB groups with the new egress quantization values for each of their egress links. During the transition between configurations, traffic can drop.

• Dynamic Load Balancing

• enhanced hash-key

• show forwarding-options enhanced-hash-key