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2.4 QoS Function
Forwarding Priority
Every output port is equipped with two transmission priority queues.
The high priority queue stores the high priority packets to be forwarded
and low priority queue stores the low priority packets.
Each receiving packet is determined and classified into one of two prior-
ity levels, high priority and low priority upon reception. The determina-
tion is based on the device QoS operating mode setting.
QoS Operating Modes
The switches provide a user selection of the following two QoS (Quality
of Service) operating modes:
1. IP DS-TOS and 802.1p Mode
This mode is called Packet Priority mode. The packet priority is depen-
dent to the content of each receiving packet. The decision method is
described as follows and applied to all input ports:
Step 1. If the receiving packet is an IPv4 packet, the switch will check the
value of Precedence field (Bit 0~2) of TOS (Type of Service field)
in IP header. By this value, the packet is classified as high priority
or low priority according to device IP-TOS priority setup table.
TOS Precedence Value
Priority Options Factory Default
0
High / Low
Low
1
High / Low
Low
2
High / Low
Low
3
High / Low
Low
4
High / Low
High
5
High / Low
High
6
High / Low
High
7
High / Low
High
