HP 6120XG HP ProCurve Series 6120 Blade Switches Advanced Traffic Management G - Page 213

Quality of Service (QoS): Managing Bandwidth More Effectively Using QoS Classifiers To Configure Quality of Service for Outbound Traffic Figure 5-14 shows an example of the ToS byte in the header for an IPv4 packet, and illustrates the diffserv bits and precedence bits in the ToS byte. (Note that the Precedence bits are a subset of the Differentiated Services bits.) Field: Destination Source MAC 802.1Q Field Type & ToS Byte ... MAC Address Address Version Packet: FF FF FF FF FF FF 08 00 09 00 00 16 08 00 45 E 0 ... Differentiated Services Codepoint Precedence Bits Rsvd. 11100000 E 0 Figure 5-14. The ToS Codepoint and Precedence Bits Table 5-7. How the Switch Uses the ToS Configuration Outbound Port ToS Option: 802.1p (Value = 0 - 7) Differentiated Services IP Packet Sent Out Depending on the value of the IP For a given packet carrying a ToS codepoint that the switch an Untagged Port Precedence bits in the packet's ToS has been configured to detect: in a VLAN field, the packet will go to one of eight • Change the codepoint according to the configured policy outbound port queues in the switch. and assign the 802.1p priority specified for the new See table 5-1 on page 5-7. codepoint in the DSCP Policy Table (page 5-51). • Do not change the codepoint, but assign the 802.1p priority specified for the existing codepoint in the DSCP Policy Table (page 5-51). Depending on the 802.1p priority used, the packet will leave the switch through one of the following queues: 1 and 2 = low priority, exits queue 1 0 or 3 = normal priority, exits queue 2 4 and 5 = medium priority, exits queue 3 6 and 7 = high priority, exits queue 4 If No-override (the default) has been configured for a specified codepoint, then the packet is not prioritized by ToS and, by default, is sent to the "normal priority" queue. 5-37