P-2002 Series User’s Guide

6.5.2.1 DSCP and Per-Hop Behavior

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-bit unused field and a 6-bit DSCP field which can define up to 64 service levels. The following figure illustrates the DS field.

DSCP is backward compatible with the three precedence bits in the ToS octet so that non- DiffServ compliant, ToS-enabled network device will not conflict with the DSCP mapping.

Figure 26 DiffServ: Differentiated Service Field

DSCPUnused

(6-bit)(2-bit)

The DSCP value determines the forwarding behavior, the PHB (Per-Hop 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 configured policies.

6.5.3 VLAN

Virtual Local Area Network (VLAN) allows a physical network to be partitioned into multiple logical networks. Only stations within the same group can communicate with each other.

Your Prestige can add IEEE 802.1Q VLAN ID tags to voice frames that it sends to the network. This allows the Prestige to communicate with a SIP server that is a member of the same VLAN group. Some ISPs use the VLAN tag to identify voice traffic and give it priority over other traffic.

6.6 QoS Configuration

Click VoIP in the navigation panel and then QoS to display the following screen.

Chapter 6 VoIP Screens

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