Excess Bandwidth Sharing and Minimum Logical Interface Shaping
The default excess bandwidth sharing proportional rate is 32.65 Mbps (128 Kbps x 255). In order to have better weighed fair queuing (WFQ) accuracy among queues, the shaping rate configured should be larger than the excess bandwidth sharing proportional rate. Some examples are shown in Table 1.
Shaping Rate |
Configured Queue Transmit Rate |
WFQ Weight |
Total Weights |
|---|---|---|---|
10 Mbps |
(30, 40, 25, 5) |
(22, 30, 20, 4) |
76 |
33 Mbps |
(30, 40, 25, 5) |
(76, 104, 64, 13) |
257 |
40 Mbps |
(30, 40, 25, 5) |
(76, 104.64, 13) |
257 |
With a 10-Mbps shaping rate, the total weights are 76. This is divided among the four queues according to the configured transmit rate. Note that when the shaping rate is larger than the excess bandwidth sharing proportional rate of 32.65 Mbps, the total weight on the logical interface is 257 and the WFQ accuracy will be the same.
When using the IOC (40x1GE IOC or 4x10GE IOC) on a Juniper Networks device, there are circumstances when you should configure excess bandwidth sharing and minimum logical interface shaping.