Comtech EF Data CDM-760 - Manual (Page 405)

Appendix K Revision 2
CDM-760 Advanced High-Speed Trunking Modem MN-CDM760
K–5
Once the Packet Processor finishes servicing every rule’s Minimum Data Rate and Weighting is
not being used, the drain of the classification rules Maximum Data Rate begins in round-robin
fashion (i.e., 1, 2, 3, 1, 2, 3, 1, 2, 3) regardless if each has a different Minimum or Maximum Data
Rate.
This type of drain mechanism ensures that every classification rule can get some fraction of the
overall capacity of the link and will not starve certain classifications rule.
You may enable WRED (Weighted Random Early Detection) on a per-classification rule basis.
With WRED enabled, a QoS classification will randomly drop packets after reaching 50% of the
QoS classification buffer depth (2500 packets of the same classification).
When you enable the Filter option for a rule, all packets that meet this classification rule will be
discarded.
K.3.3.3 DiffServ Mode
DiffServ (Differentiated Services) QoS mode is fully compliant with RFC standards. In this mode,
the system automatically configures the rules with dSCPC code points, priority values, and
WRED. You can only configure the service rate and drop precedence levels for Assured
Forwarding (ASFD) classes.
K.4 Weighting
K.4.1 Overview
This section describes weighted QoS scheduling in addition to the round-robin scheduling for
queues. You may enter the weights while configuring queues, similar to configuring other QoS
parameters such as Min BW (minimum bandwidth), Max BW (maximum bandwidth), Priority,
etc.
K.4.2 Weights
Weight is a user-configurable parameter. Enter a weight in the range from 1 to 100. You cannot
assign a null value (0) – this is invalid. The default value is 100. The scheduler drains more data
from a weight=8 queue than a weight=7 queue under the same priority, and so on.
Weights are applicable in Min/Max and Max/Priority mode. However, when Max/Priority Mode
is selected as the QoS mechanism, weights are considered only if multiple queues are
configured in same priority group, and at least one of the weight entries is different from the
others. When queue weights are the same within the same priority group, that group is handled
by round-robin scheduling.
K.4.2.1 Order of Scheduling
For Max/Priority Mode – Weights are applied to all queues that have not reached the assigned
Max BW limit.