Appendix J. Return Group Qos (Quality Of Service; Overview; Qos List Of Supported Rfcs (Requests For Comment; Qos Terminology - Comtec CDM-840 Installation And Operation Manual

Appendix J. RETURN GROUP QoS
J.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-840 Remote Router
provides Return 2-level Group QoS while classifying packets up to Layer 4 (the Transport Layer)
of the Open Systems Interconnection (OSI) Model.
QoS is fully integrated with ACM (Adaptive Coding and Modulation), dSCPC (Dynamic Single
Carrier Per Channel), and header and payload compression to achieve highest bandwidth
utilization while providing desired levels of service.
J.1.1

QoS List of Supported RFCs (Requests for Comment)

RFC No. Description
"Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers"
2474
Nichols, K., Blake, S., Baker, F. and D. Black, December 1998
"An Architecture for Differentiated Services"
2475
Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. and Weiss, W., December 1998
"Assured Forwarding PHB"
2597
Heinanen, J., Baker, F., Weiss, W. and J. Wrocklawski, June 1999
"An Expedited Forwarding PHB"
2598
Jacobson, V., Nichols, K. and K. Poduri, June 1999
J.1.2

QoS Terminology

• CIR – CIR (Committed Information Rate) is used to reserve capacity through the QoS system.
CIR is entered in kbps but is enforced in 1k Bytes per second increments. The CIR will be
honored unless there is not enough bandwidth/symbols on the transmitter.
•
CIR Availability – The reported CIRs Availability statistics is the percentage of time over the
last 1, 15 or 60 minutes for which the CIR was demanded of the QoS system and the system
was able to honor the packet throughput demand. CIR Availability is intended to provide a
metric for operators to trend over time to determine if there is enough satellite bandwidth
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