Appendix M. Quality Of Service (Qos; Overview; Qos Terminology - Comtech EF Data CDM-425 Installation And Operation Manual

Appendix M. QUALITY of SERVICE
M.1

Overview

Quality of Service (QoS) enables a network to use WAN bandwidth more efficiently by managing
delay, jitter (delay variation), throughput, and packet loss.
The CDM-425 Advanced Satellite Modem incorporates two Per Hop Behavior (PHP) QoS
methods – Layer 2 QoS and Layer 3 QoS:
•
Layer 2 QoS is available on the CDM-425 Advanced Satellite Modem by default when
the optional IP Packet Processor card is either not installed, or is installed but disabled.
Layer 2 QoS is based on OSI model Layer 2 header parameters such as IEEE 802.1q
VLAN priority field, and is also based on the CDM-425's physical Ethernet port.
•
Layer 3 QoS requires the optional IP Packet Processor card to be installed and enabled,
and the Advanced QoS FAST option must be purchased and activated. Layer 3 QoS is
based on OSI model Layer 3 to Layer 7 protocol header parameters.
M.1.1

QoS Terminology

•
Latency – Latency is the amount of delay that is measured, in milliseconds, from the
Ethernet interface of the near-end modem to the Ethernet interface of the far-end
modem.
•
Jitter – Jitter is the amount of variation that is measured, in milliseconds, between two
consequent frames at the receiving end.
Appendix M
CDM-425 Advanced Satellite Modem
M–1
Revision 0
(QoS)
MN-CDM-425