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Link scheduler configuration task list
163
SmartWare Software Configuration Guide 
13 • Link scheduler configuration
The type-of-service (TOS) byte in an IP header specifies precedence (priority) and type of service (RFC791, 
RFC1349). The precedence field is defined by the first three bits and supports eight levels of priority. The next 
four bits—which are set by the 
set ip tos
 command—determine the type-of-service (TOS). 
Historically those bits had distinct meanings but since they were never consistently applied routers will ignore 
them by default. Nevertheless you can configure your routers to handle specific TOS values and SmartWare 
allows you to inspect the TOS value in the ACL rules and to modify the TOS value with the link scheduler 
set 
ip tos
 command. 
Mode: Source
Specifying the precedence field
The 
set ip precedence
 command specifies the precedence marking applied to packets of the class name. Pre-
cedence and DSCP markings cannot be used at the same time.
The type-of-service (TOS) byte in an IP header specifies precedence (priority) and type of service (RFC791, 
RFC1349). The precedence field is defined by the first three bits and supports eight levels of priority. The low-
est priority is assigned to 0 and the highest priority is 7.
The 
no
 form of this command disables precedence marking.
Mode: Source
Specifying differentiated services codepoint (DSCP) marking
Differentiated services enhancements to the Internet protocol are intended to enable the handling of “traffic-
classes” throughout the Internet. In this context the IP header TOS field is interpreted as something like a 
Table 5. TOS values and their meaning
TOS Value SmartWare Value
Meaning
1000
8
Minimize delay.
0100
4
Maximize throughput.
0010
2
Maximizes reliability.
0001
1
Minimize monetary costs.
0000
0
All bits are cleared, normal service, “default TOS.”
Command
Purpose
node(src)[name]#set ip tos value Defines the type-of-service (TOS) value applied to packets of for the 
selected class or policy name. Standard ToT values are 0, 1, 2, 4, 
and 8, as given in 
15 can be configured.
Command
Purpose
node(src)[name]#set ip precedence value
Defines the precedence marking value applied to pack-
ets of for the selected class or policy name. The range 
for value is from 0 to 7, but only values from 0 to 5 
should be used.