AT-TQ2403 Management Software User's Guide

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802.1q and DSCP tags

IEEE 802.1q is an extension of the IEEE 802 standard and is responsible for QoS provision. One purpose of 802.1q is to prioritize network traffic at the data link/ MAC layer.

The 802.1q tag includes a three-bit field for prioritization, which allows packets to be grouped into various traffic classes. Eight priority levels are defined. The highest priority is seven, which might go to network- critical traffic (voice). The lowest priority level is zero, this is used as a best-effort default, it is invoked automatically when no other value has been set.

Note: It is important to note that 802.1q prioritization will not work unless QoS and WMM are enabled. WMM must be enabled on both the AP and on the client connecting to the AP.

The flow diagram below outlines the way in which tags are retrieved and traffic prioritized on a network.

Figure 48: 802.1q Tag Retrieving Flow Diagram