User's Manual

Chapter 21 Voice 191
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 th
e three precedence bits in the ToS octet so that non-DiffServ
compliant, ToS-enabled network device will not conflict with the DSCP mapping.
Figure 117 Di
ffServ: Differentiated Service Field
DSCP
(6-bit)
Unused
(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.
21.8.2 Phone Services Overview
Supplementary services such as call hold, call waiting, and call transfer. are generally available from
your VoIP service provider. The Router supports the following services:
• Call Hold
• Call Waiting
• Making a Second Call
•Call Transfer
•Call Forwarding
• Three-Way Conference
•Internal Calls
• Call Park and Pickup
•Do not Disturb
 To take full advantage of the supplementary phone services available through the Router's
phone ports, you may need to subscribe to the services from your VoIP service provider.
1. The Router does not support DiffServ at the time of writing.