122 Link
Scheduler Configuration
Software Configuration Guide Release 2.10, Revision 1.00
(RFC791, RFC1349). The precedence field is defined by the first three bits and supports eight levels of
priority. The lowest priority is assigned to 0 and the highest priority is 7. The values 6 and 7 are
15.8.5 Specifying the Type-Of-Service (TOS) Field
The
set ip tos
command specifies the type-of-service (TOS) field value applied to packets of the class
name
. TOS and DSCP markings cannot be used at the same time. The
no
form of this command
disables TOS marking.
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). Only one of these bits can be turned on. Each bit determines a specific method for the router
to select a path.
TOS
Value
SmartWare
Value
Meaning
1000
8
This bit minimizes the delay. The delay bit tells the link scheduler to
choose high speed to minimize delay. This bit would typically be set for
voice.
0100
4
This bit maximizes throughput. The throughput bit specifies high capacity
links used for bulk transfers.
0010
2
This bit maximizes reliability. Routing protocols and network
management applications use this for fault tolerant paths.
0001
1
This bit minimizes monetary costs. The cost bit is for low priority
applications such as NNTP and signifies the lowest cost path.
0000
0
If all bits are cleared normal service is selected, which is referred as
"default TOS".
Table 15-2: TOS Values and their Meaning
Because TOS values are integers rather than sets of bits, computing the logical OR of two TOS values
is not meaningful. For example, it would be a serious error for a router to choose a low delay path for
a packet whose requested TOS was 1110 simply because the link scheduler noted that the former
delay bit
was set.
Procedure
Defining the type-of-service (TOS) field
Mode
Source
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
. Valid values for
value
are 0, 1, 2, 4, and 8,
as given in Table 15-2.
15.8.6 Specifying the Precedence Field
The
set ip precedence
command specifies the precedence marking applied to packets of the class
name
. Precedence 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
Summary of Contents for SmartWare Release 2.10
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