Ruijie RG-S2900G-E Series, Руководство по настройке

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Configuration Guide QoS Configuration
port is associated with a policy-map but has no DSCP value set for it, the switch will
assign the priority for the messages of this classification by performing the default
behavior: following the priority information contained in the layer-2 packet header of
the message or the default priority of the port.
Note
The above three criteria may apply simultaneously on the same port.
In this case, they will take effect according to the sequence 3, then 2
and then 1. In other words, the ACLs work first for the classifying
operation. When it fails, the criteria 2 will be used, and so on. Here, if
the QoS trust mode of the port is enabled, criteria 2 and 1 will be used
to get the QoS information directly from the message or the port;
otherwise, default DSCP value 0 will be assigned for the messages
failing the classifying operation.
For IP messages, the switch classifies the messages according to the following criteria:

If the port trust mode is Trust ip-precedence, it extracts from the ip precedence field
(3 bits) of the IP message and fills the CoS field (3 bits) of the output message.

If the port trust mode is Trust cos, it extracts directly the CoS field (3 bits) of the
message and overwrite the ip precedence field (3 bits) of the message. There are the
following two cases. Case 1 is that the layer-2 packet header does not contain User
Priority bits, and now the CoS value is got from the default CoS value of the message
input port. Case 2 is that the layer-2 packet header contains User Priority bits, and
now the CoS is got directly from the packet header.

If the Policy-map associated with the port is using the ACLs classifying based on the
ip access-list (extended), the associated ACLs will be matched by getting the source
IP address, destination IP address, Protocol field and layer-4 TCP/UDP port field of
the message, to determine the DSCP value of the message, and the CoS value is
determined according to the mapping from DSCP to CoS. Note that, if a port is
associated with a policy-map but has no DSCP value set for it, the switch will use the
above criteria 1 and 2 to determine the priority.
Just like the criteria for non-IP message classifying, the above classifying criteria can
apply on the same port at the same time. In this case, they will take effect according to the
sequence 3, then 2 and then 1.
For the details of the CoS-to-DSCP map and IP-precedence-to-DSCP map, see the
descriptions below.
Policing
The Policing action happens after the data classifying is completed. It is used to constrain
the transmission bandwidth occupied by the classified dataflow. The Policing action will
check every message in the classified dataflow. If the message is occupying more
bandwidth as allowed by the police that applies on that dataflow, the message will be
treated specially, either to be discarded or assigned with another DSCP value.
In the QoS processing flow, the Policing action is optional. If no Policing action is