Comtech EF Data CDM-625 Installation And Operation Manual page 445

CDM-625 Advanced Satellite Modem
Quality of Service (QoS)
QoS Example 4
1. VLAN-based Layer 2 QoS mode is selected.
2. The modem data rate is set to 1 Mbps.
3. Four streams of VLAN ingress traffic is sent to the modem with VLAN Priorities set to 7, 5, 3,
and 1, respectively.
4. The data rate for each stream is set to 500 Kbps.
QUESTION: What is the total output data rate and what are the individual port output data
rates?
ANSWER "A" – For HW Ver. Rev 2.1 and newer:
•
Based on Table 20-1 for a modem Tx bandwidth of 1 Mbps, the QoS output bandwidth is set
to 1 Mbps.
• Total Input data rate is 4X 500 Kbps = 2 Mbps
•
Based on Table 20-2, the VLAN Priorities 7, 5, 3, and 1 are mapped, respectively, to L2 QoS
Priorities 4, 3, 2, and 1.
• Since the modem Tx bandwidth and QoS output data rates are the same, there is no need
for normalization.
•
The data rate for each port is as follows:
VLAN
Priority
7
5
3
1
Total ►
ANSWER "B" – For HW Ver. Rev 1.1 and older:
• Based on Table 20-1 for a modem Tx bandwidth of 1 Mbps, the QoS output bandwidth is set
to 1 Mbps.
•
Total Input data rate is 4X 500 Kbps = 2 Mbps.
•
Based on Table 20-2, the VLAN Priorities 7, 5, 3, and 1 are mapped, respectively, to L2 QoS
Priorities 4, 3, 2, and 1.
L2 QoS
Input Data Rate
Priority
4 500 Kbps
3 500 Kbps
2 500 Kbps
1 500 Kbps
2 Mbps
20–7
QoS Output Data Remaining Data Rate (After
Rate Serving the Priority Queue)
500 Kbps
500 Kbps
0 Kbps
0 Kbps
1 Mbps
Revision 13
MN-CDM625
Output Data
Rate
500 Kbps 500 Kbps
0 Kbps 500 Kbps
0 Kbps 0 Kbps
0 Kbps 0 Kbps
0 Kbps 1 Mbps