Allied Telesis AT-FS970M Series - Manual (Page 254)

Chapter 22: Quality of Service (QoS)
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value. The mark CoS action causes a port to change the CoS value of
all ingress packets that match the filtering criteria with the specified
CoS value.
 A port can have only one QoS policy.
 A QoS policy can be assigned to more than one port.
 QoS classifies ingress packets, but does not process egress packets.
As a result, you must apply QoS policies to the ingress ports of the
designated traffic flows.
 QoS policies for static port trunks or LACP trunks must be assigned to
the individual ports of the trunks.
 A QoS policy can have multiple filtering criteria. For example, a QoS
policy may classify traffic based on a source IP address, a VLAN ID,
and a DSCP value.
 A QoS policy that has more than one filtering criterion selects traffic
that matches all specified filtering criteria.