Comtech EF Data CDM-425, Installation And Operation Manual

Page: 719 / 744

CDM-425 Advanced Satellite Modem
Revision 0
Appendix M M–7 MN-CDM-425
QoS Example 5
SETUP:
•
Port- and VLAN-based Layer 2 QoS mode is selected.
•
Port Layer 2 QoS Priorities are set as follows:
o
Port 1 priority is set to 1
o
Port 3 priority is set to 3
o
Ports 2 and 4 priorities are set to trunk mode (native disabled)
•
The modem data rate is set to 4000 Kbps.
•
The ingress traffic on Port 1 is set to 2 Mbps.
•
The ingress traffic on Port 3 is set to 1600 Kbps.
•
The ingress traffic on Port 2 is set to 2000 Kbps with a VLAN Priority of 1.
•
The ingress traffic on Port 4 is set to 800 Kbps with a VLAN Priority of 7.
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 M-1 for a modem Tx bandwidth of 4 Mbps, the QoS output
bandwidth is set to 4 Mbps.
•
Since the modem Tx bandwidth and QoS output data rates are the same, there is
no need for normalization.
•
Based on Table M-2, the VLAN Priorities 7 and 1 are mapped, respectively, to L2
QoS Priorities 4 and 1.
•
The data rate for each port is as follows:
Port
VLAN
Priority
L2 QoS
Priority
Input Data
Rate
QoS Output Data
Rate = Modem
Output Data Rate
Remaining Data Rate
(After Serving the
Priority Queue)
4 7 (b111) 4 800 Kbps 800 Kbps 3200 Kbps
3 N/A 3 1600 Kbps 1600 Kbps 1600 Kbps
2 1 (b001) 1 2 Mbps 800Kbps 800Kbps
1 N/A 1 2 Mbps 800 Kbps 800 Kbps
Total ► 5.3 Mbps 4 Mbps 0 Mbps
1. Layer 2 QoS can be enabled only when the optional Packet Processor is not enabled.
2. Layer 2 QoS is implemented on System on Chip (SoC) hardware with a total queue
memory of 1 Mbits (128 Kbytes). Layer 2 QoS therefore cannot accept traffic bursts
requiring more than 128 Kbytes of storage.