23
The default priority maps (as shown in "Appendix A Default priority maps") are available for priority
mapping. They are adequate in most cases. If a default priority map cannot meet your requirements,
you can modify the priority map as required.
Priority trust mode on a port
The priority trust mode on a port determines which priority is used for priority mapping table lookup.
Port priority was introduced to use for priority mapping in addition to the priority fields carried in
packets. The Switch Series provides the following priority trust modes:
• Using the 802.1p priority carried in packets for priority mapping.
Table 3 Priority mapping results of trusting the 802.1p priority (when the default
dot1p-lp priority mapping table is used)
802.1p priority carried in
packets
Local precedence Queue ID
0 2 2
1
0 0
2 1 1
3 3 3
4 4 4
5 5 5
6 6 6
7
7 7
NOTE:
When the 802.1p priority carried in packets is trusted, the port priority is used for priority mapping fo
packets which do not carry VLAN tags (namely, do not carry 802.1p priorities.) The priority mapping
results are the same as not trusting packet priority, as shown in Table 5.
• Using the DSCP carried in packets for priority mapping.
Table 4 Priority mapping results of trusting the DSCP (when the default dscp-dot1p and
dot1p-lp priority mapping tables are used)
DSCP value carried in
packets
Local precedence Queue ID
0 to 7 2
2
8 to 15
0 0
16 to 23 1
1
24 to 31 3
3
32 to 39 4
4
40 to 47 5
5
48 to 55 6
6
56 to 63
7 7
• Using the port priority as the 802.1p priority for priority mapping. The port priority is user
configurable.
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