R3102-R3103-HP 6600/HSR6600 Routers ACL and QoS Configuration Guide

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Appendix C Introduction to packet precedences
IP precedence and DSCP values
Figure 39 ToS and DS fields
As shown in Figure 39, 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
p
recedence (decimal) IP
p
recedence (binar
y
) Descri
p
tion
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 (binar
y
) Descri
p
tion
46 101110 ef
10 001010 af11
12 001100 af12
14 001110 af13
18 010010 af21
20 010100 af22