Configuring Quality of Service 443Configuring QoS Global SettingsQuality of Service (QoS) provides the ability to implement QoS and priority queuing within a network.The Global Settings page contains a field for enabling or disabling QoS. It also contains a field for selectingthe Trust mode. The Trust mode relies on predefined fields within the packet to determine the egress queue.In addition, the Global Settings page enables defining queues as either Strict Priority (SP) or WeightedRound Robin (WRR).To open the Global Settings page, click Quality of Service→ QoS Parameters → Global Settings in thetree view.Figure 9-1. Global SettingsThe Global Settings page contains the following sections:• QoS Settings• Queue SettingsQoS Settings• Quality of Service — Enables or disables managing network traffic using Quality of Service.• Trust Mode — Determines which packet fields are used to classify packets entering the device.When no rules are defined, the traffic containing the predefined CoS or DSCP packet field is mappedaccording to the selected trust mode. Traffic not containing a predefined packet field is mapped to thebest effort queue (q2). The possible Trust Mode field values are:– CoS (802.1p) — The egress queue assignment is determined by the IEEE802.1p VLAN prioritytag (VPT) or by the default VPT assigned to a port. The device default is the IEEE802.1p.– DSCP — The egress queue assignment is determined by the DSCP field.NOTE: The interface Trust settings overrides the global Trust setting.
