H3C Technologies H3C WX3000 Series Unified Switches - Manual (Page 350)

37-6
z
The local precedence is only of local significance. A local precedence corresponds to a specific
output queue. Packets with higher local precedence values take precedence over those with lower
precedence values and will be processed preferentially.
z
The drop precedence determines which packets are dropped preferentially. The higher the drop
precedence, the more likely a packet is dropped.
The device does not support marking drop precedence for packets.
A device can operate in one of the following two priority trust modes when assigning precedence to
received packets:
z
Packet priority trusted mode
z
Port priority trusted mode
In terms of priority trust mode, the priority mapping process is shown in Figure 37-4 .
Figure 37-4 Assigning precedence to received packets in different trust modes
Receiving port
Trust port priority
Assign the port priority of the
receiving port to the 802.1p
precedence of the packet and
look up the priority mapping
table based on the packet
priority to assign priority
parameters (including local
precedence and drop
precedence) for the packet
Look up the priority mapping
table based on the packet
priority to assign priority
parameters (including local
precedence and drop
precedence) for the packet
N
Y
Packet
As for packet priority trusted mode, you can configure to trust the following packet priority:
z
802.1p precedence
z
DSCP precedence
Trusting the 802.1p precedence
In this mode, you can specify to process the received packets in one of the following two ways.
z
Keeping the original packet precedence unchanged (the default mode)
z
Replacing the original packet precedence with the corresponding one (the automap mode).
If a packet does not carry 802.1p precedence, the device uses the priority of the receiving port as the
802.1p precedence of the packet and then looks up the COS-precedence-to-other-precedence
mapping table for the corresponding precedence.