Comtech EF Data CDM-840, Инструкция по установке и эксплуатации, Страница: 71 / 110

CDM-840 Remote Router Revision 0
Ethernet Management MN-CDM840
5–25
For any active configuration, note the following:
QoS Control
Mode – Use the drop-down menu to select QoS operation as Off , D iffserv , Max/Priority , or
Min/ Max . Note the following:
•
Off – When selected, QoS is disabled. Instead of an operable page, the ‘ Configuration |
WAN | QoS’ page appears as shown in Figure 5-15(a) .
•
DiffServ –When selected, the CDM-840 operates in Differentiated Services (DiffServ)
Mode to make it fully compliant to the Differentiated Services QoS RFC (Request For
Comments) standards. The ‘
Configuration | WAN | QoS’ page appears as shown in
Figure 5-15(b) .
•
Max/Priority – Provides multi-level traffic prioritization with the ability to limit
maximum traffic per priority class. The ‘ Configuration | WAN | QoS’ page appears as
shown in Figure 5-16(a) .
•
Min/Max – Provides a Committed Information Rate (CIR) to each user-defined class of
traffic with the ability to allow a higher burstable rate depending on availability. The
‘
Configuration | WAN | QoS’ page appears as shown in Figure 5-16(b) .
SAR – Segmentation and Reassembly (SAR) is an adaptive process; at lower data rates, it
improves the jitter and latency performance for high priority packets. Use the drop-down menu to
select SAR as
Disable or Enable .
Once the desired configuration settings have been made in this section, click [Submit] as needed
to save these changes.
The Differentiated Services section appears only when QoS Control Mode = Diffserv.
Differentiated Services
Priority – IP traffic is prioritized based upon the DSCP (DiffServ Code Points) Class Selector
Precedence.
Per-Hop Behavior (PHB) – Traffic class that determines how packets will be forwarded.
Codepoint (DSCP) – Codepoint value in Type of Service (ToS) byte in IP header.
The user has the option of configuring each queue to one of the following attributes (the valid
operating range for each item is provided in brackets):
Service Rate (Kbps) [ 0.000 / (Tx Data Rate)] – The minimum bandwidth will be served first
among the Assured Forwarding (ASFD) classes in case of bandwidth availability once Class
Selector 7 through Class Selected 1 have been serviced.
Drop Precedence – ASFD Class 4 through 1 Code Points (b100xx0, b011xx0, b010xx0, and
b001xx0) carry the drop precedence value (xx). In case of network congestion, a Weighted
Random Early Detection (WRED) congestion avoidance algorithm is imposed on these queues to
drop the packets randomly rather than ‘tail drop.’
•
Low Drop Precedence (% full) [0 – 100] – In case of congestion, the WRED is applied
after the queue depth exceeds the configured percentage value assigned for the Drop
Precedence value b001.
•
Med. Drop Precedence (% full) [0 – 99] – In case of congestion, the WRED is applied
after the queue depth exceeds the configured percentage value assigned for the Drop
Precedence value b010.