Cisco Cisco SG200-26P 26-port Gigabit PoE Smart Switch Manuel De Maintenance

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Quality of Service
QoS Properties
Cisco Small Business SF200E Series Advanced Smart Switch
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The switch supports eight egress queues for each port or LAG. Queue1 has the 
lowest priority and queue 8 has the highest priority.
The pages in the Quality of Service menu enable you to define the properties of 
the queues, and to associate to the queues the traffic that has particular 
characteristics or arrives on specific interfaces. You can also create rate limit 
profiles that define criteria for determining if a port is receiving more traffic than it 
can handle. You can then assign the rate limit profiles to ports.
QoS Properties
You can configure switch ports to assign traffic to egress queues based on the 
priority information encoded in Ethernet frames or IP packet headers. Or traffic 
might use a default priority value configured on the port where it arrives. When a 
port is configured to use the encoded priority value [such as the 802.1p, IP 
precedence, or DSCP (Differentiated Services Code Point) value], it is considered 
trusted port. A port that is configured to use its own priority value, rather than the 
value encoded in the frame or packet, to make queue assignment decisions is 
considered untrusted.
If a port is configured as trusted but the frame or packet does not have priority 
information, the default port priority is assigned to the packet. The default port 
priority is zero.
You can use the Interface Settings page to change the value of the VLAN Priority.
You can use the QoS Properties page to define a port as trusted or untrusted and 
to configure which priority values it trusts. 
To configure the trust mode on a port or LAG:
STEP 1
Click Quality of Service > QoS Properties in the navigation window.
STEP  2
Select a filter from the Interface Type menu to display ports or LAGs in the Trust 
Mode Configuration Table.
STEP  3
Select the interface to configure and click Edit.
STEP  4
To specify the type of priority values to use to determine the egress queues of the 
packets, select one of the following trust modes:
untrusted—The port assigns its own default 802.1p priority (0).
trust dot1p—The port uses the 802.1p priority value in VLAN-tagged 
Ethernet frames. For untagged frames, the default priority is assigned.