ZyXEL Communications NVG2053, Руководство пользователя

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Chapter 17 Voice
NVG2053 User’s Guide
192
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 84 DiffServ: Differentiated Service Field
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.
17.9.2 Phone Services Overview
Supplementary services such as call hold, call waiting, and call transfer. are
generally available from your VoIP service provider. The NVG2053 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
Note: To take full advantage of the supplementary phone services available through
the NVG2053's phone ports, you may need to subscribe to the services from
your VoIP service provider.
DSCP
(6-bit)
Unused
(2-bit)