Comtec CDM-840 - Page 307

CDM-840 Remote Router MN-CDM840
Appendix J Revision 3
J–13
Case 2 example – The Pri-Weighted QoS rules are configured as follows:
Queue Min BW (kbps) Max BW (kbps)
Delta Max Bytes
(Max-Min kbps)
Weight Allowed BW (kbps)
1
16
32
16
9
–
2
32
64
32
8
–
3
48
128
64
7
–
4
64
64
0
6
–
Total ►
160
288
112
30
240
The total allowed bandwidth is 240 kbps. The total minimum bandwidth is 160 kbps. The
minimum bandwidth is therefore less than the available bandwidth.
The QoS Scheduler Calculation Solutions table for the Case 2 example is as follows:
Queue
Round 1
Round 2
Round ‘N’
Final
(kbps)
Weight
Given
(kbps)
Leftover
(kbps)
Weight
Given
(kbps)
Leftover
(kbps)
Weight
Given
(kbps)
Leftover
(kbps)
1
9
30
14
–
–
–
–
–
–
16
2
8
26.672
–
8
7.472
2.144
–
–
–
32
3
7
23.328
–
7
6.528
–
7
2.144
–
32
4
–
–
–
–
–
–
–
–
–
–
Total ►
24
80
14
15
14
2.144
7
2.144
0
80
This table shows the result of the steps taken to calculate the individual allocated
bandwidths:
1. After the minimum bandwidth is satisfied, there is 80 kbps of bandwidth remaining. This
leftover bandwidth is distributed to all queues whose maximum bandwidth hasn’t been
reached. In this example, only Queues 1, 2, and 3 still have an unmet maximum
bandwidth.
Since Queue 4’s minimum and maximum bandwidths are the same, Queue 4 will be
taken out of the algorithm for distributing the remaining quantum.
The remaining total weight is (9 + 8 + 7) = 24.
2. Each bandwidth share is then calculated based on the remaining total weight (24) and
bandwidth availability (10000 bytes) after the minimum bandwidth is served (20000
bytes):
o Queue 1 = 10000 * (9 / 24) = 3750 bytes (30 kbps)
o Queue 2 = 10000 * (8 / 24) = 3334 bytes (26.6 kbps)
o Queue 3 = 10000 * (7 / 24) = 2916 bytes (23.328 kbps)
3. After Round 1 of quantum distribution, Queue 1 requires only 16 kbps (2000 bytes) to
reach its maximum bandwidth, hence the remaining 14 kbps (3750 − 2000 = 1750