DSCP

When configuring an IP interface in the Tunnels Library, you can specify a Differential Service Code Point (DSCP) value. (DSCP is only supported on GMIP and GRE tunnels.) This value is a 6-bit field in the IP header and specifies the Per-Hop Behavior (PHB). DSCP allows traffic to be classified so that each traffic class can be managed differently, ensuring preferential treatment for higher-priority traffic on the network.

For GigaVUE-VM traffic to receive preferential treatment in the network, a specific DSCP value can be chosen by the service provider per tunnel. The DSCP values fall into the following three categories:

• Default PHB—best effort traffic. Select a value of 0 for DSCP to specify Default PHB.
• Expedited Forwarding (EF) PHB—dedicated to low-loss, low-latency traffic. Select EF for DSCP to specify this PHB.
• Assured Forwarding (AF) PHB—gives assurance of delivery under prescribed conditions. There are four classes of AF vales and each class is further divided by drop probability. The classes are defined in Table 1: AF Behavior Group Classes.

In addition to these three categories, values from 0 to 63 are allowed.

Table 1: AF Behavior Group Classes

Drop Probability	Class 1	Class 2	Class 3	Class 4
Low	AF11 (DSCP 10)	AF21 (DSCP 18)	AF31 (DSCP 26)	AF41 (DSCP 34)
Medium	AF12 (DSCP 12)	AF22 (DSCP 20)	AF32 (DSCP 28)	AF42 (DSCP 36)
High	AF13 (DSCP14)	AF23 (DSCP 22)	AF33 (DSCP 30)	AF43 (DSCP 38)