Patton electronic 07M2160-GS, 2160 Series manual IP Dscp Priority, Service by WRR

41,25 Queue 20

40,35 Queue 21

4,5 Queue 2

6,7 Queue 3

Figure 26. Service by WRR

IP DSCP Priority

Differentiated Services Overview. Differentiated Services (DiffServ) is a class of service (CoS) model that enhances best-effort Internet services by differentiating traffic by users, service requirements and other criteria. Packets are specifically marked, allowing network nodes to provide different levels of service, as appropriate for video playback, voice calls or other delay-sensitive applications, via priority queuing or bandwidth allocation.

DiffServ defines a new DS (Differentiated Services) field to replace the Type of Service (ToS) field in the IP header. The DS field contains a 2-bits unused field and 6-bits DSCP field which can define up to 64 service levels. Figure 27 shows the DS field:

Figure 27. Differentiated Services field

The DSCP value used to identify 64 levels (26=64) of service determines the forwarding behavior that each packet gets across the DiffServ network. Based on the marking rule different kinds of traffic can be marked for different priorities of forwarding. Resources can then be allocated according to the DSCP values and the con- figured policies. Table 11 shows how the bits are used in the DSCP field.