1.3 IEEE 802.1p QoS
The RC-GS1024 switch supports 802.1p priority queuing Quality of Service, which
is an implementation of the IEEE802.1p 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.
Tag untag 0
1
2
3
4
5
6
7
Priority Level
TC0
TC1
TC2
TC3
Weight Value
1
2
4
8
Mapping QoS on the Switch
The Switch has four priority levels labeled TC0, TC1, TC2 and TC3. The untagged
packets and the eight IEEE802.1p priority tags defined by the standard are
mapped to the four level queues used on the Switch. TC3 has the highest priority
of the four priority level queues while TC0 has the lowest priority on the Switch.
The untagged packets and eight priority tags, specified in IEEE802.1p are mapped
to the switch’s priority tags as follows:
The untagged packets, packets with priority tag 1 and 2 are assigned to the
switch’s TC0 level queue.
Packets with priority tag 0 and 3 are assigned to the switch’s TC1 level
queue.
Packets with priority tag 4 and 5 are assigned to the switch’s TC2 level
queue.
Packets with priority tag 6 and 7 are assigned to the switch’s TC3 level
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 weight value of TC0, TC1, TC2 and
TC3 is 1:2:4:8.
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