Comtech EF Data CDM-570A - Manual (Page 561)

L–1
Appendix L. ADVANCED
QUALITY OF SERVICE (QoS)
OPTION
L.1 Overview
Advanced Quality of Service (QoS) enables a network to use WAN bandwidth more efficiently by
managing delay, jitter (delay variation), throughput, and packet loss. It is based on OSI model to
Layer 7 protocol header parameters.
Advanced QoS requires that you install the optional IP Packet Processor, and that you purchase
and activate the Advanced QoS FAST Option. Contact Comtech EF Data Product Support for
further information.
QoS scheduling operates on modem Tx bandwidth with 1-byte resolution, so there is no further
trimming or clipping data rate after the QoS scheduler.
QoS is implemented with at least one 1-second burst at maximum data rate.
QoS systems use a strict priority QoS scheduling algorithm. Excluding the default queue, the
QoS system has up to 32 QoS queues with eight configurable priorities rules. The QoS system
creates a separate queue for each rule to store the incoming stream of packets. (In this
appendix, ‘QoS rules’ and ‘QoS queues’ are interchangeable).
QoS systems incorporates WRED (Weighted Random Early Detection) based congestion
avoidance algorithm in addition to tail drop.
The CDM-570A/L-IP incorporates four Per Hop Behavior (PHP) QoS modes of operation:
• Mode 1 – Max/Pri (QoS Rules based on Maximum Bandwidth and Priority)
• Mode 2 – Min/Max (QoS Rules based on Minimum and Maximum Bandwidth)
• Mode 3 – DiffServ (Differentiated Services)
• Mode 4 – VLAN – Priority/Max (VLAN 802.1q)