Comtech EF Data CDM-625A Installation And Operation Manual page 669

Appendix R. QUALITY
R.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-625A 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-625A 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-625A'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.
R.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.
OF
R–1
SERVICE
(Q S)
O
,