VSC7511 datasheet(147/324 Pages) MICROSEMI

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Functional Descriptions

VMDS-10488 VSC7511 Datasheet Revision 4.2

132

•

=32

∗5/10 = 16

•

= 32*5/15 = 10.67 (rounded up to 11)

•

= 32*5/20 = 8

•

= 32*5/20 = 8

•

= 32*5/30 = 5.33 (rounded down to 5)

Due to the rounding off, these costs result in the following bandwidth distribution, which is slightly off

compared to the desired distribution:

•

Input 0: 4.92%

•

Input 1: 9.85%

•

Input 2: 14.32%

•

Input 3: 19.70%

•

Input 4: 19.70%

•

Input 5: 31.51%

3.12.4

Round Robin

The round robin (RR) uses a simple round robin algorithm where each participating input is served one

after another. RR is enabled when SE_CFG.SE_DWRR_CFG>0 and SE_CFG.RR_ENA = 1. The

participating inputs are then inputs 0 through SE_CFG.SE_DWRR_CFG-1. Anything from 0 to 12

weighted inputs can participate.

The RR algorithm is frame-based and does not take the frame lengths into account.

3.12.5

Shaping and DWRR Scheduling Examples

This section provides examples and additional information about the use of the egress shapers and

scheduler. The following assumes a scheduler element is connected to the egress queues.

3.12.5.1 Mixing DWRR and Shaping Example

•

Output from scheduler element is shaped down to 500 Mbps.

•

Queues 7 and 6 are strict and queues 5 through 0 are weighted.

•

Queue 7 is shaped to 100 Mbps.

•

Queue 6 is shaped to 50 Mbps.

•

The following traffic distribution is desired for queue 5 through 0:

: 5%, Q1: 10%, Q2: 15%, Q3: 20%, Q4: 20%, Q5: 30%.

•

Each queue receives 125 Mbps of incoming traffic.

The following table lists the DWRR configuration and the resulting egress bandwidth for the various

queues.

Table 103 •

Example of Mixing DWRR and Shaping

Queue

Distribution

of Weighted

Traffic

Configuration

Costs/Weights

(Cn/Wn)

Result: Egress Bandwidth

32 / 1

1/(1+2+2.9+4+4+6.4) × (500 – Mbps – 150 Mbps) = 17.2 Mbps

10%

16 / 2

2/(1+2+2.9+4+4+6.4) × (500 – Mbps – 150 Mbps) = 34.5 Mbps

15%

11 / 2.9

2.9/(1+2+2.9+4+4+6.4) × (500 – Mbps – 50 Mbps) = 50.1 Mbps

20%

8 / 4

4/(1+2+2.9+4+4+6.4) × (500 – Mbps – 150 Mbps) = 68.9 Mbps

20%

8 / 4

4/(1+2+2.9+4+4+6.4) × (500 – Mbps – 150 Mbps) = 68.9 Mbps

30%

5 / 6.4

6.4/(1+2+2.9+4+4+6.4) × (500 – Mbps – 150 Mbps) = 110.3 Mbps

50 = Mbps

100 = Mbps

Sum:

100%

500 = Mbps

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