LevelOne GSW-2457 - Manual (Page 7)

3
¾ Supports MAC address auto-learning and auto-aging
¾ LED indicators for monitoring power, link, speed and activity
¾ Rack-mountable steel case
¾ Internal power supply
1.3 IEEE 802.1p QoS
The GSW-1657/GSW-2457 16/24-port Gigabit Ethernet Switch supports
802.1p priority queuing Quality of Service, which is an implementation of the
IEEE 802.1p standard. With 802.1p QoS function, you can reserve bandwidth
for important functions that require a large bandwidth or have a high priority,
such as VoIP (Voice-over Internet Protocol), web browsing applications or
video conferencing. The Switch has separate hardware queues on every
physical port which packets from various applications are mapped to and
assigned a priority to. The illustration below shows how 802.1p priority queuing
is implemented on the Switch.
Mapping QoS on the Switch
The Switch has four priority queues labeled 0, 1, 2 and 3. The untagged
packets and the eight IEEE 802.1p priority levels defined by the standard are
mapped to the four class queues used on the Switch. Among these four priority
queues on the Switch, Class 3 has the highest priority, while Class 0 has the
lowest priority and Class 3 has higher priority compared with Class 2. The
Untagged packets and eight priority tags, specified in IEEE 802.1p are mapped
to the switch’s priority tags as follows:
The Untagged packets, priority 1 and 2 are assigned to the switch’s Class 0
queue.
Priority 0 and 3 are assigned to the switch’s Class 1 queue.
Priority 4 and 5 are assigned to the switch’s Class 2 queue.
Priority 6 and 7 are assigned to the switch’s Class 3 queue.
The Switch uses WRR (Weighted Robin Round) for scheduling. WRR
queue-scheduling algorithm schedules all the queues in turn and every queue
can be assured of a certain service time. The default value of QoS mode on
this Switch is “weight 1:2:4:8” from Class 0 to Class 3 queue in turn.