Qos Groups; Qos Group Matching - Comtec CDM-840 Installation And Operation Manual

CDM-840 Remote Router
Appendix J
J.2

QoS Groups

Including the default queue, each QoS Group has up to 32 QoS Rules with eight configurable
priorities. The QoS systems:
•
Create a separate queue for each rule to store the incoming stream of packets. (In this
appendix, 'QoS rules' and 'QoS queues' are interchangeable.)
• Use a strict priority QoS scheduling algorithm. For QoS Group priority numbering, the lower
the priority number, the higher the priority. For example, a Priority 1 queue schedules and
drains before a Priority 2 queue; similarly, Priority 2 packets will schedule and drain before
Priority 3 packets, etc.
Each QoS queue is implemented to support at least one (1)-second burst at the maximum
data rate of the Tx Carrier of the modem.
•
Incorporate WRED (Weighted Random Early Detection) based congestion avoidance
algorithm in addition to tail drop. WRED is designed to avoid congestion by progressively
increasing the chance of an incoming packet being dropped once the QoS queue has
reached 50% of capacity. After the queue is 50% full, then the random chance of dropping a
packet increasing up to 100% when the queue is full.
J.2.1

QoS Group Matching

QoS Group Matching allows you to match an incoming packet to the desired QoS Group. Once a
packet has been matched to a QoS Group, then the configured QoS Rule Matching criteria are
used to determine where the packet is inserted into the QoS queue.
Note that QoS Group Matching is global across all QoS Groups. You must make sure that the
QoS Groups throughout the system do not share the same matching criteria The FW Ver. 1.6.2.X
Packet-to-QoS Group Matching criteria is as follows (by order of preference):
1. Matching Subnet + VLAN
2. Matching Subnet
3. Matching VLAN
4. Default QoS Group
Matching is absolute, not partial. If a QoS Group has a Subnet and VLAN attribute, then the
traffic must match BOTH attributes to be classified to use the group. Classification starts with
the most stringent matching criteria (Subnet and VLAN) and continues down the hierarchy until
a match is found. If there is more than one QoS Group with the same attributes (which should
be avoided), the last matching QoS Group will be used.
J–7
MN-CDM840
Revision 3