Chapter 15 Bandwidth Management
P-660HWP-Dx User’s Guide
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15.10 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.

15.10.1 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 132 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.
#This is the number of an individual bandwidth management rule.
Active This displays whether the rule is enabled. Select this check box to have the P-
660HWP-Dx apply this bandwidth management rule.
Enable a bandwidth management rule to give traffic that matches the rule priority
over traffic that does not match the rule.
Enabling a bandwidth management rule also allows you to control the maximum
amounts of bandwidth that can be used by traffic that matches the rule.
Rule Name This is the name of the rule.
Destination Port This is the port number of the destination. 0 means any destination port.
Priority This is the priority of this rule.
Bandwidth (kbps) This is the maximum bandwidth allowed for the rule in kbps.
Modify Click the Edit icon to go to the screen where you can edit the rule.
Click the Remove icon to delete an existing rule.
Apply Click Apply to save your changes to the P-660HWP-Dx.
Cancel Click Cancel to begin configuring this screen afresh.
Table 92 Bandwidth Management: Rule Setup (continued)
LABEL DESCRIPTION
DSCP
(6-bit)
Unused
(2-bit)