Mapping IP Precedence
The Type of Service (ToS) octet in the IPv4 header includes three precedence
bits defining eight different priority levels ranging from highest priority for network
control packets to lowest priority for routine traffic. The default IP Precedence
values are mapped one-to-one to Class of Service values (i.e., Precedence
value 0 maps to CoS value 0, and so forth). Bits 6 and 7 are used for network
control, and the other bits for various application types. ToS bits are defined in
the following table.
Priority Level
Traffic Type
7
Network Control
6
Internetwork Control
5
Critical
4
Flash O verride
3
Flash
2
Immediate
1
Priority
0
Routine
Command Attributes
> IP Precedence/DSCP Priority Status – Selects IP Precedence, DSCP, or dis-
ables both priority services.
> IP Precedence Priority Table – Shows the IP Precedence to CoS map.
> Class of Service Value – Maps a CoS value to the selected IP Precendence
value. Note that “0” represents low priority and “7” represent high priority.
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