Traffic Priority; Queue Scheduling - Huawei Quidway S6500 Series Operation Manual

Operation Manual - QoS/ACL
Quidway S6500 Series Ethernet Switches

2.1.8 Traffic Priority

The Ethernet Switch can deliver priority tag service for some special packets. The tags
include TOS, DSCP and 802.1p, etc., which can be used and defined in different QoS
modules.

2.1.9 Queue Scheduling

When congestion occurs, several packets will compete for the resources. The queue
scheduling algorithms are used to overcome the problem. Here introduce Strict-Priority
Queue (SP) queue scheduling algorithm.
1) SP
Packets sent via this
interface
Figure 2-1 SP
The SP is specially designed for the key service application. A significant feature of the
key service is requiring for priority to enjoy the service to reduce the responding delay
when congestion occurs. Take 8 egress queues for each port as example, SP divides
the queue of port into up to 8 kinds, from high-priority queue to low-priority queue
(which are shown as the Queue 7, 6, 5, 4, 3, 2, 1 and 0 in turn) with sequentially
reduced priority.
During the progress of queue dispatching, strictly following the priority order from high
to low, the SP gives preference to and sends the packets in the higher-priority queue
first. When the higher-priority queue is empty it will send the packets in the
lower-priority group. In this way, put the packets of higher priority service in the
higher-priority queue and put the packets of lower priority, like e-mail, in the
lower-priority queue, can guarantee the key service packets of higher priority are
high priority
Classify
Low priority
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2-3
Chapter 2 QoS Configuration
queue 7
queue 6
Packets sent
queue 5
queue 4
Dequeue Sending queue
queue 3
queue 2
queue 1
queue 0