User manual
Publication date: Feb., 2013
Revision A3
159
Controls the default QoS class, i.e., the QoS class for frames not classified in any other
way. There is a one to one mapping between QoS class, queue and priority. A QoS class of
0 (zero) has the lowest priority.
z DP level :
Controls the default DP level, i.e., the DP level for frames not classified in any other way.
z PCP :
Controls the default PCP for untagged frames.
z DEI :
Controls the default DEI for untagged frames.
z Tag Class. :
Shows the classification mode for tagged frames on this port.
Disabled: Use default QoS class and DP level for tagged frames.
Enabled: Use mapped versions of PCP and DEI for tagged frames.
Click on the mode in order to configure the mode and/or mapping.
z DSCP Based :
Click to Enable DSCP Based QoS Ingress Port Classification.
z Buttons:
Save – Click to save changes.
Reset- Click to undo any changes made locally and revert to previously saved
values.
NOTE: DP level :
Every incoming frame is classified to a Drop
Precedence Level (DP level), which is used throughout the
device for providing 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, map to DP value is 0 or 1.
When 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 Puts, Egress Port 7 Rate be set
with 500M. Port 1 Puts will includes two kinds packet:
a. PCP & DEI = 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