ZyXEL Communications MSC1000G Series, User Manual

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Chapter 11 Profile Screens
Management Switch Card User’s Guide
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• IPQoS limits the data rate of traffic flowing through the Device’s physical queues.
• You can use 1, 2, 4, or 8 queues.
• A VLC13XXG port connection that uses or falls back to ADSL2+ mode uses IPQoS instead of ATM
QoS.
11.23.1 IPQoS Parameters
Setting up IPQoS involves these parameters:
• PIR (Peak Information Rate): This is the maximum data rate allowed for the downstream traffic
(traffic flowing to the subscribers).
• CIR (Committed Information Rate): This is the guaranteed data rate for the downstream traffic.
• PBS (Peak Burst Size): This is the maximum burst size allowed for the downstream traffic when
the burst data rate is between the predefined PIR and CIR.
• CBS (Committed Burst Size): This is the guaranteed burst size for the downstream traffic when
the burst data rate is smaller than the predefined CIR.
• Level: This is the Strict Priority Queuing (SPQ) priority level (0~7) for each queue. 0 is the lowest
priority and 7 is the highest. SPQ services queues by priority only. As traffic comes into the
switch, traffic in the highest priority queue (Q7) is transmitted first. When that queue empties,
traffic in the next highest-priority queue (Q6) is transmitted until Q6 empties, and then Q5 traffic
is transmitted and so on. If higher priority queues never empty, then traffic on lower priority
queues never gets sent. SPQ does not automatically adapt to changing network requirements.
• Weight: This is the queue weight (1~127). The Device uses Weighted Round Robin (WRR)
scheduling to service queues of the same priority level on a rotating basis based on their queue
weight. The higher a queue’s weight, the more service it gets. This queuing mechanism is highly
efficient in that it divides any available bandwidth across the different traffic queues and returns
to queues that have not yet emptied.
11.23.2 IEEE 802.1p to IPQoS Queue Mapping
The following table shows the system’s default IEEE 802.1p to switch queues and the (fixed) switch
queue mapping to IPQoS queue mapping.
• IEEE 802.1p Priority : This column represents the IEEE 802.1p priorities of IEEE 802.1p
(priority) tagged packets destined for a subscriber.
Table 181
IEEE 802.1p to IPQoS Default Queue Mapping
IEEE 802.1P
PRIORITY SWITCH
QUEUES IPQOS PROFILE
WITH 1 QUEUE IPQOS PROFILE
WITH 2 QUEUES IPQOS PROFILE
WITH 4 QUEUES IPQOS PROFILE
WITH 8 QUEUES
0 2 Q0 Q0 Q1 Q2
1 0 Q0 Q0 Q0 Q0
2 1 Q0 Q0 Q0 Q1
3 3 Q0 Q0 Q1 Q3
4 4 Q0 Q1 Q2 Q4
5 5 Q0 Q1 Q2 Q5
6 6 Q0 Q1 Q3 Q6
7 7 Q0 Q1 Q3 Q7