CDM-570/570L Satellite Modem with Optional IP Module Revision 4
IP Module Ethernet Interface Overview MN/CDM570L.IOM
Algorithm Payload size File Set Ratio
ADLC 1472 Calgary 1.76
ADLC 1000 Calgary 1.76
ADLC 500 Calgary 1.77
ADLC 100 Calgary 2.09
ADLC 1472 Canterbury 1.71
ADLC 1000 Canterbury 1.72
ADLC 500 Canterbury 1.74
ADLC 100 Canterbury 2.04
LZS 1472 Calgary 1.66
LZS 1000 Calgary 1.66
LZS 500 Calgary 1.68
LZS 100 Calgary 1.97
LZS 1472 Canterbury 1.61
LZS 1000 Canterbury 1.62
LZS 500 Canterbury 1.63
LZS 100 Canterbury 1.91

15.4.4 Quality of Service

Quality of Service (QoS) is an optional feature of the IP Module. The user may select one
of three modes of QoS operation:
• Mode 1 – QoS Rules based on Maximum Bandwidth and Priority
• Mode 2 – QoS Rules based on Minimum and Maximum Bandwidth
• Mode 3 – DiffServ
QoS Segmentation and Reassembly (SAR) - Packet Segmentation and Reassembly
(SAR) is enabled automatically while QoS is enabled. However, SAR is an adaptive
process; it will trigger only if the packet latency exceeds the threshold value (default to
20 msec). Latency value is calculated based on the satellite transmission bandwidth.
There is no minimum segment size. However if the last segment is less than 16 bytes,
then it will be appended to the previous segment excluding satellite HDLC header in
order to avoid satellite overhead and consumption of CPU cycles.
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