Allocating Weight 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. In order 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, consider a logical interface configuration with
five units, as shown in Table 233.
Table 233: 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:
Select the excess bandwidth-sharing proportional rate
to be the maximum CIR among all the logical interfaces: 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 although
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.
