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# Weight Allocation with Only Shaping Rates or Unshaped Logical Interfaces

Logical interfaces with only shaping rates (PIRs) or unshaped logical interfaces (units) are given a weight of 10. A logical interface with a small guaranteed rate (CIR) might get an overall weight less than 10. To allocate a higher share of the excess bandwidth to logical interfaces with a small guaranteed rate in comparison to the logical interfaces with only shaping rates configured, a minimum weight of 20 is given to the logical interfaces with guaranteed rates configured.

For example, a logical interface configuration with five units is shown in Table 1.

Table 1: Allocating Weights with PIR and CIR on Logical Interfaces

Logical Interface (Unit)

Traffic Control Profile

WRR Percentages

Weights

Unit 1

PIR 100 Mbps

95, 0, 0, 5

10, 1, 1, 1

Unit 2

CIR 20 Mbps

25, 25, 25, 25

64, 64, 64, 64

Unit 3

PIR 40 Mbps, CIR 20 Mbps

50, 30, 15, 5

128, 76, 38, 13

Unit 4

Unshaped

95, 0, 0, 5

10, 1, 1, 1

Unit 5

CIR 1 Mbps

95, 0, 0, 5

10, 1, 1, 1

The weights for these units are calculated as follows:

• The excess bandwidth-sharing proportional rate is the maximum CIR among all the logical interfaces which is 20 Mbps (unit 2).

• Unit 1 has a PIR and unit 4 is unshaped. The weight for these units is 10.

• The weight for unit 1 queue 0 is 9.5 (10 x 95%), which translates to a hardware weight of 10.

• The weight for unit 1 queue 1 is 0 (0 x 0%) but though the weight is zero, a weight of 1 is assigned to give minimal bandwidth to queues with zero WRR.

• Unit 5 has a very small CIR (1 Mbps), and a weight of 20 is assigned to units with a small CIR.

• The weight for unit 5 queue 0 is 19 (20 x 95%), which translates to a hardware weight of 18.

• Unit 3 has a CIR of 20 Mbps, which is the same as the excess bandwidth-sharing proportional rate, so it has a total weight of 255.

• The weight of unit 3 queue 0 is 127.5 (255 x 50%), which translates to a hardware weight of 128.