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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
ackets
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 for 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
ackets Local
recedence
Queue ID
0 to 7 0 0
8 to 15
1 1
16 to 23 2 2
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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