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Prestige 660H/HW Series User’s Guide
203 Chapter 18 Media Bandwidth Management Advanced Setup
18.9.1 DiffServ
DiffServ is a class of service (CoS) model that marks packets so that they receive specific per-
hop treatment at DiffServ-compliant network devices along the route based on the application
types and traffic flow. Packets are marked with DiffServ Code Points (DSCPs) indicating the
level of service desired. This allows the intermediary DiffServ-compliant network devices to
handle the packets differently depending on the code points without the need to negotiate
paths or remember state information for every flow. In addition, applications do not have to
request a particular service or give advanced notice of where the traffic is going.
18.9.1.1 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 107 DiffServ: 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.
18.9.2 Media Bandwidth Management Class Configuration
Configure a bandwidth management class in the Class Configuration screen. You must use
the Media Bandwidth Management - Summary screen to enable bandwidth management on
an interface before you can configure classes for that interface.
To add a child class, click Media Bandwidth Management, then Class Setup. Click the Add
Child-Class button to open the following screen.