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QoS Example 1
QUESTION:
If the modem Tx data rate is set to 180 Kbps, then what is the QoS Tx data rate?
ANSWER:
The QoS Tx data rate can be set from 64 Kbps to 1 Mbps, in 64 Kbps steps. If the
180 Kbps modem Tx data rate is not in 64 Kbps step size, then the QoS Tx data rate
will be the next 64 Kbps, which is 196 Kbps.
M.2.2
Flow Control
In Layer 2 QoS mode, the CDM-425 supports Ethernet-based pause frame control (IEEE 802.3).
Flow control can be enabled or disabled independently in any of the LAN ports.
M.2.3
Port-based Layer 2 QoS
When selecting Port-based Layer 2 QoS, each port's priority is configurable to a QoS queue
priority of 1 (lowest) to 4 (highest). In this mode, irrespective of traffic type, all traffic ingress on a
particular port is treated with the priority assigned to that port.
In the event any port is overdriven with ingress traffic, if there is insufficient queue memory to
store the packet, then the packet will be dropped and drop stats will be incremented against that
port.
QoS Example 2
SETUP:
•
•
•
•
QUESTION:
What is the total output data rate and what is individual ports output data rate?
ANSWER:
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Appendix M
Port-based Layer 2 QoS mode is selected.
Port Layer 2 QoS Priorities are set as follows:
Port 1 priority is set to 1
o
Port 2 priority is set to 2
o
Port 3 priority is set to 3
o
Port 4 priority is set to 4
o
The modem data rate is set to 1 Mbps.
The ingress traffic on each port is set to 250 Kbps.
Based on Table M-1 for a modem Tx bandwidth of 1 Mbps, the QoS output
bandwidth is set to 1 Mbps.
Total Input data rate is 4X 250 Kbps = 1 Mbps
The output Data rate = 1 Mbps
Each ports data rate = 250 Kbps
CDM-425 Advanced Satellite Modem
M–3
Revision 0
MN-CDM-425
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