HP 6120XG HP ProCurve Series 6120 Blade Switches Advanced Traffic Management G - Page 195

Quality of Service (QoS): Managing Bandwidth More Effectively Using QoS Classifiers to Configure Quality of Service for Outbound Traffic 3. Assign the policies to the codepoints in the selected packet types. The specified DSCP policies overwrite the original DSCPs on the selected packets, and use the 802.1p priorities previously configured in the DSCP policies in step 2. Figure 5-9. Example of Policy Assignment to Outbound Packets on the Basis of the DSCP in the Packets Received from Upstream Devices Details of QoS IP Type-of-Service IP packets include a Type of Service (ToS) byte. The ToS byte includes: ■ A Differentiated Services Codepoint (DSCP): This element is com- prised of the upper six bits of the ToS byte). There are 64 possible codepoints. • In the switches covered in this guide, the default qos configuration includes some codepoints with 802.1p priority settings for AssuredForwarding and Expedited Forwarding (codepoint 101110), while others are unused (and listed with No-override for a Priority). Refer to figure 5-9 on page 5-34 for an illustration of the default DSCP policy table. Using the qos dscp map command, you can configure the switch to assign different prioritization policies to IPv4 packets having different codepoints. As an alternative, you can configure the switch to assign a new codepoint to an IPv4 packet, along with a corresponding 802.1p priority (0-7). To use this option in the simplest case, you would: 5-24