Quanta Cloud Technology QuantaMesh QNOS5, Configuration Manual

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Minimum bandwidth guarantee: A percentage of the port’s maximum negotiated bandwidth
reserved for the queue.
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Scheduler type – strict/weighted:
– S t r i c t priority scheduling gives an absolute priority, with traffic in the highest priority queues
always sent first, and traffic in the lowest priority queues always sent last.
– W e i g h t e d scheduling requires a specification of priority for each queue relative to the other
queues, based on their minimum bandwidth values.
5.1.3.1. Supported Queue Management Methods
The switch supports the following methods, configurable per-interface-queue, for determining which packets
are dropped when the queue is full:

Taildrop: Any packet forwarded to a full queue is dropped regardless of its importance.

Weighted Random Early Detection (WRED) drops packets selectively based their drop
precedence level.
For each of four drop precedence levels on each WRED-enabled interface queue, you can configure the
following parameters:
– M i n i m u m Threshold: A percentage of the total queue size below which no packets of the
selected drop precedence level are dropped.
– M a x i m u m Threshold: A percentage of the total queue size above which all packets of the
selected drop precedence level are dropped.
– D r o p Probability: When the queue depth is between the minimum and maximum thresholds, this
value provides a scaling factor for increasing the number of packets of the selected drop precedence
level that are dropped as the queue depth increases.
5.1.3.2. CoS Configuration Example
Figure 22 illustrates the network operation as it relates to CoS mapping and queue configuration.
Four packets arrive at the ingress port 0/10 in the order A, B, C, and D. Port 0/10 is configured to trust the
802.1p field of the packet, which serves to direct packets A, B, and D to their respective queues on the
egress port. These three packets utilize the 802.1p to CoS Mapping Table for port 0/10.
In this example, the 802.1p user priority 3 is configured to send the packet to queue 5 instead of the default
queue 3. Since packet C does not contain a VLAN tag, the 802.1p user priority does not exist, so Port 0/10
relies on its default port priority (2) to direct packet C to egress queue 1.