3Com SUPERSTACK 3 3250, Implementation Manual

Page: 49 / 132

How Traffic Prioritization Works 49
The 802.1D standard specifies eight distinct levels of priority (0 to 7),
each of which relates to a particular type of traffic. The priority levels and
their traffic types are shown in
Figure 11 in order of increasing priority.
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 11 .
Figure 11 IEEE 802.1D traffic types
Figure 11 illustrates IEEE 802.1D traffic types as well as associated priority
levels and how they are mapped to the four supported traffic queues.
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.