H3C S5120-EI Series Operation Manual page 559

Figure 3-4 Priority mapping process in the case of supporting trusting port priority
Trust packet
priority
N
Trust port
priority
Packet
Receiving
port
When trusting packet priority, S5120-EI series Ethernet switches provide the following two priority trust
modes:can trust one of the following two priority types:
Trusting the DSCP precedence of received packets. In this mode, the switch searches the
dscp-dot1p/dp/dscp mapping table based on the DSCP precedence of the received packet for
the 802.1p precedence/drop precedence/DSCP precedence to be used to mark the packet. Then
the switch searches the dot1p-lp mapping table based on the marked 802.1p precedence for the
corresponding local precedence and marks the received packet with the local precedence.
Trusting the 802.1p precedence of received packets. In this mode, if a packet is received without
an 802.1q tag, the switch takes the priority of the receiving port as the 802.1p precedence of the
packet and then based on the priority searches the dot1p-dp/lp mapping table for the local/drop
precedence for the packet. If packet is received with an 802.1q tag, the switch searches the
dot1p-dp/lp mapping table based on the 802.1p precedence in the tag for local/drop precedence
for the packet.
The default dot1p-lp/dp mapping and dscp-dot1p/dp/dscp mapping provided by S5120-EI series
Ethernet switches are shown in the following two tables.
dot1p-dp: 802.1p-priority-to-drop-precedence mapping table
dot1p-lp: 802.1p-priority-to-local-precedence mapping table
dscp-dot1p: DSCP-precedence-to-802.1p-priority mapping table
dscp-dp: DSCP-precedence-to-drop-precedence mapping table, applicable to only IP packets
dscp-dscp: DSCP-precedence-to-DSCP-precedence mapping table, applicable to only IP packets
Table 3-4 The default values of dot1p-lp mapping and dot1p-dp mapping
Imported priority value
802.1p precedence (dot1p)
0
1
2
3
4
5
6
7
Search for the set of precedence
values corresponding to the trusted
type of priority of the packet in the
corresponding priority mapping
tables and assigns the set of
matching precedence values to the
packet
Search for the local precedence
Y
corresponding to the port priority
of the receiving port in the
802.1p-to-local precedence
mapping table, and assign the
local precedence to the packet
dot1p-lp mapping
Local precedence (lp)
2
0
1
3
4
5
6
7
3-5
dot1p-dp mapping
Drop precedence (dp)
0
0
0
0
0
0
0
0