Supermicro SuperBlade SBM-GEM-X2C+, Руководство пользователя

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Superblade Network Modules User’s Manual
6-16
6-7 Quality of Service
Quality of Service (QoS) helps a network user to reserve a guaranteed bandwidth for
some critical application functions that require a high bandwidth and high priority.
Applications such as video, audio streaming, VoIP and video conferencing must have a
certain amount of bandwidth to maintain their operation correctly. QoS allows user to
prioritize network traffic, thereby providing better services for those applications with a
higher priority.
The switch supports 802.1p priority queuing QoS based on the priority bit in a frame’s
VLAN header. The 802.1p priority bit, if present in the frame, specifies the priority of the
frame during forwarding. The 802.1p standard uses eight (0-7) priority levels for network
traffic. Priority level 7 is the highest priority. Priority level 0 is the lowest level.
Priority Queues
Four priority queues are provided for each port. The priority queues are labeled from 3
to 0. Priority queue 3 has highest priority while queue 0 has lowest priority. The switch
transmits the frames based on the priority of the queue, not the priority tag. Frames in a
higher priority queue are served more often than frames in a lower priority queue.
User configurable mapping (priority queue assignment) between the eight 802.1p
priority classes and the four priority queues is provided. If the incoming frame is
untagged, the switch uses the priority field in the per-port default priority (configurable in
the P
ORT
folder) to assign a frame to a priority queue. If the incoming frame is tagged or
priority-tagged, the switch uses the priority field in the incoming frame to assign the
frame to a priority queue.
The scheduling for transmission among the four priority queues is accomplished by one
of the two user-configurable schemes: strict (fixed) priority and weighted round-robin.
For strict priority based scheduling, the packets which were put in the higher priority
queue are transmitted first. If there are multiple frames with different priority tags in the
same priority queue, the frame with higher priority level is transmitted first. After all
frames in the higher priority queue have been transmitted, the frames in the lower
priority queue will start transmitting.
For the weighted round-robin based scheduling, the number of packets served in the
priority queue is determined by the weight number. After those packets are transmitted,
the service moves to transmit the packets in the next queue. Therefore, a higher priority
queue should have a higher weight number than a lower priority queue. The weight
number is from 1 to 15 for the switch. If each queue has same weight number, then each
queue has an equal opportunity to transmit frames just like in round-robin queuing.
To configure the QoS, click the Q
O
S folder on the left-hand side bar. It should display as
shown in Figure 6-13 .
The Q
O
S S
ETTING
sets the priority relationship between the four queues, selects the
scheduling method for those queues, associates packets of specific priorities to specific
queues, and specifies a “weight” for each queue.