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Quality of Service (QoS) is used to ensure smooth network traffic and that high priority traffic receives preferential treatment. The traffic classification is done by an Access Control List (ACL), and only traffic which meets the ACL criteria is subject to QoS classification. QoS Basic mode allows the definition of a specific domain in the network as trusted. Within that domain, packets are marked with the VLAN Priority Tag (VPT) 802.1p value in Layer 2 and the Differentiated Service Code Point (DSCP) value for IPv4 or Traffic Class (TC) value for IPv6 in Layer 3. Nodes in this domain use these fields to assign packets to a specific output queue. It is recommended that you disable the trusted mode at the ports where the CoS/802.1p and/or DSCP values in the incoming packets are not trustworthy. Otherwise, the performance of your network may be negatively affected.
This article explains how to setup the QoS Basic mode global settings on ESW2-350G Switches.
Step 1. Log in to the web configuration utility to choose Quality of Service > QoS Basic Mode > Global Settings. The Global Settings page opens:
Step 2. At the Trust Mode field, click one of the radio buttons that are defined as follows:
• CoS/802.1p — Click this option if you want the Traffic to be mapped to queues based on the VLAN Priority Tag (VPT) field in the VLAN tag, or based on the per-port default CoS/802.1p value (if there is no VLAN tag on the incoming packet). Refer to the article entitled Configuration of CoS/802.1p to Queue Mapping on ESW2-350G Switches for for further details on mapping of the CoS/802.1p values to queues.
• DSCP — Click this option if you want all the IP traffic to be mapped to queues based on the Differentiated Services Code Point (DSCP) field in the IP header. Refer to the article entitled Map Differentiated Services Code Point to Queue on Sx500 Series Stackable Switches for further details on mapping of the DSCP to queues. If traffic is not IP traffic, it is mapped to the best effort queue.
• CoS/802.1p-DSCP — Click this option if you want to choose either CoS/802.1p rules or DSCP rules, based upon whichever has been set.
Note: Step 3 does nothing if CoS/802.1p is clicked in Step 2.
Step 3. (Optional) Check the Override Ingress DSCP check box to replace the current DSCP values in the incoming packets with new DSCP values based on the DSCP Override Table.
Timesaver: Skip to Step 7 if you did not check the Override Ingress DSCP check box.
Step 4. If Override Ingress DSCP is enabled, click DSCP Override Table to reconfigure DSCP. A new window appears to configure the DSCP values as shown below.
Step 5. Choose the appropriate DSCP value from the drop-down list. The values are in the range of 0 to 63. These values are dependent upon the configuration of service providers. Typically the higher the DSCP value, the higher the priority.
• DSCP In — This column displays the DSCP values of the incoming packets that can to be mapped to an alternative value.
• DSCP Out — Choose an option to indicate mapping of the outgoing value. By default, the DSCP In and DSCP Out are the same.
Step 6. (Optional) Click the Restore Defaults button if you want to restore the default values in the DSCP override table.
Step 7. Click Apply to save the changes in the DSCP Override Table.
Step 8. Click Apply to save the changes in the Global Settings page to the Running Configuration.