116
Input priority value
dscp-dp mapping
dscp-dot1p mapping
56 to 63
0
7
Appendix C Introduction to packet precedences
IP precedence and DSCP values
Figure 39 ToS and DS fields
As shown in
, the ToS field in the IPv4 header contains 8 bits, where the first 3 bits (0 to 2)
represent IP precedence from 0 to 7. The Traffic Classes field in the IPv6 header contains 8 bits,
where the first 3 bits (0 to 2) represent IP precedence from 0 to 7. According to RFC 2474, the ToS
field in the IPv4 header or the Traffic Classes field in the IPv6 header is redefined as the DS field,
where a DSCP value is represented by the first 6 bits (0 to 5) and is in the range of 0 to 63. The
remaining 2 bits (6 and 7) are reserved.
Table 8 IP precedence
IP precedence (decimal)
IP precedence (binary)
Description
0 000
Routine
1 001
priority
2 010
immediate
3 011
flash
4 100
flash-override
5 101
critical
6 110
internet
7 111
network
Table 9 DSCP values
DSCP value (decimal)
DSCP value (binary)
Description
46 101110
ef
10 001010
af11
12 001100
af12
14 001110
af13
18 010010
af21