3Com 3C17300A Implementation Guide - Page 53

How Traffic Prioritization Works 53 You cannot alter the mapping of priority levels 0 - 7 to the traffic queues. These priority levels are fixed to the traffic queues as shown in Figure 13. Figure 13 IEEE 802.1D traffic types Classification Ingress Port 802.1D 802.1p Service levels Best effort 0 Background 1 Spare 2 Business Critical 3 Multimedia 4 Video 5 Voice 6 Network Control 7 Strict Priority Queue Scheduling Low Priority Queue Egress Port High Priority Queue Figure 13 illustrates IEEE 802.1D traffic types as well as associated priority levels and how they are mapped to the two supported traffic queues. The 802.1D service level of the packet is not altered by the Switch 4200 Series. DiffServ traffic classification DiffServ is an alternative method of classifying traffic so that different levels of service can be applied to it on a network. DiffServ is a layer 3 function; and the service to be applied is contained within the DSCP field, which is in the IP header of a packet.