3Com 3824 Implementation Manual page 55

Switch 3812 and Switch 3824
Classification
DSCP
Ingress Port
EtherType
Figure 15 Advanced traffic prioritization and marking
Configured Marking and
Service Levels Remarking
Service Level DSCP
Service Level DSCP
Service Level DSCP
Service Level DSCP
1 The packet received at the ingress port is checked for any of the
supported traffic classification methods (DSCP, Ethertype, Protocol) to
identify the traffic.
2 The classification in an incoming packet will be compared with the
predefined classifications in the Switch, and if there is a match, the
configured service level associated with the classified traffic will be
applied.
3 The service level associated with the classifier may cause the 802.1p tag
to be remarked, if the packet already has an 802.1p tag, and the DSCP
value in IP packets to be remarked.
4 The Switch will remark the 802.1p tag and DSCP field.
5 It is the priority associated with the packet that is used to direct it to the
appropriate queue. This is determined as follows:
If the packet matches a classifier with a configured service level
specifying that the DSCP or 802.1p tag should be re-marked, then the
packet is re-marked with the configured DSCP value and or the
802.1p priority.
How Traffic Prioritization Works
Mapping is predefined
and not configurable
802.1p
Priority
802.1D
1
802.1D
2
0
3
4
5
802.1D
6
802.1D
7
Traffic Queues
Queue 1 is lowest priority
Queue 8 is highest priority
Queue 1
Queue 2
Queue 3
Queue 4
Queue 5
Queue 6
Queue 7
Queue 8
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Egress Port