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Chapter 5
Packet Classification and Labelling
E-NIT-CTC-20041213-0013 v0.5
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5.2.2 Using TOS, DSCP or Precedence
Introduction In this section we will explain the parameters that need to be set to enable QoS
throughout the entire network. This means that these values are only of significance
for outgoing fraffic. The tables below describe the values used when configuring
IPQoS by setting the TOS byte, using DSCP or by setting the Precedence bits.
TOSmarking When using TOS a very fine definition of the Quality of Service can be made. This is
only of use when the whole network supports QoS by TOS.
TOS
Precedence
When using Precedence the QoS definition is narrowed down to 8 values
!
Only one type of of IPQoS can be used at the time.
TOSmarking values Discription
disable Disables the TOS marking.
enable Enables the TOS marking.
TOS values Description
1..255 Sets the TOS bits in the IP header to the coresponding
value.
Precedence values Description
routine will set the precedence bits to 000. (lowest
priority)
priority will set the precedence bits to 001.
immediate will set the precedence bits to 010.
flash will set the precedence bits to 011.
flash-override will set the precedence bits to 100.
CRITIC-ECP will set the precedence bits to 101.
internetwork-control will set the precedence bits to 110.
network-control will set the precedence bits to 111. (highest priority)
number 0..7 0..7.