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Appendix Packet precedences
IP precedence and DSCP values
Figure 250 DS field and ToS field
As shown in Figure 250, the ToS field of the IP header contains 8 bits: the first 3 bits (0 to 2) represent
IP precedence from 0 to 7. According to RFC 2474, the ToS field of the IP header is redefined as the
differentiated services (DS) field, where a differentiated service code point (DSCP) value is
represented by the first 6 bits (0 to 5) and is in the range 0 to 63. The remaining 2 bits (6 and 7) are
reserved.
Table 119 Description on IP precedence
IP precedence (decimal) IP precedence (binary) Keyword
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 120 Description on DSCP values
DSCP value (decimal) DSCP value (binary) Keyword
46 101110 ef
10 001010 af11
12 001100 af12
14 001110 af13
18 010010 af21
20 010100 af22
22 010110 af23
26 011010 af31
28 011100 af32
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