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NOTE:
DP level
: Every incoming frame is classified to a Drop
Precedence Level (DP level), which is used throughout the
device to provide congestion control guarantees to the
frame, according to what was configured for that specific DP
level.
PCP
: PCP is an acronym for Priority Code Point. It is a 3-bit
field storing the priority level for the 802.1Q frame.
DEI
: DEI is an acronym for Drop Eligible Indicator. It is a 1-bit
field in the VLAN tag.
Actual PCP is Pri column in Vlan tag packet. DEI is cfi column
PCP value from 0~7. It can be used for priority definition.
DEI value is 0 or 1. It is settable and map to the DP value of 0
or 1. When the ingress Qos class value is the same, then
through DP level value to define the priority. DP value larger
will be dropped first.
Ex: From port 1 input 1G pkts, egress port 7 rate be set with
500M. Port 1 pkts will includes two kinds packet:
a.
PCP & DEI = 0 0, via configured map to Qos class &
DP level = 1 , 0
b.
PCP & DEI = 0 1, via configured map to Qos class &
DP level = 1 , 1
Result will find (a) Packet all past, and (b) packets all drop.