Owner's Manual

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In a Switch, multiple queues per port are often provided to give preference to certain packets
over others based on user-defined criteria. When a packet is queued for transmission within a
port, the rate at which it is processed depends on how the queue is configured and the amount of
traffic present within other queues on the port. If a delay is necessary, packets are held in the
queue until they are authorized for transmission.
Global Settings
There are two options for applying QoS information onto packets: the 802.1p Class of Service
(CoS) priority field within the VLAN tag of tagged Ethernet frames, and Differentiated Services
(DiffServ) Code Point (DSCP). Each port on the Switch can be configured to trust one of the
packet fields (802.1p , DSCP or DSCP+802.1p). Packets that enter the Switch's port may carry
no QoS information as well. If so, the Switch places such information into the packets before
transmitting them to the next node. Thus, QoS information is preserved between nodes within the
network and the nodes know which label to give each packet. A trusted field must exist in the
packet for the mapping table to be of any use. When a port is configured as untrusted, it does not
trust any incoming packet priority designations and uses the port default priority value instead to
process the packet.