84
Input priority value dscp-dp map dscp-dot1p map
40 to 47 0 5
48 to 55 0 6
56 to 63 0 7
Appendix B Introduction to packet precedences
IP precedence and DSCP values
Figure 26 ToS and DS fields
As shown in Figure 26, the ToS field in the IP header contains eight bits. The first three bits (0 to 2)
represent IP precedence from 0 to 7. According to RFC 2474, the ToS field is redefined as the
differentiated services (DS) field, where a DSCP value is represented by the first six bits (0 to 5) and
is in the range 0 to 63. The remaining two bits (6 and 7) are reserved.
Table 10 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 11 DSCP values
DSCP value (decimal) DSCP value (binary) Description
46 101110 ef
10 001010 af11
12 001100 af12
14 001110 af13
M
B
Z
RFC 1122
IP Type of Service (ToS)
RFC 791
Must
Be
Zero
RFC 1349
IPv4 ToS
byte
07615432Bits:
Preced
ence
Type of
Service
076
DSCP
Class Selector
codepoints
Differentiated Services
Codepoint (DSCP)
RFC 2474
Currently
Unused
DS-Field
(for IPv4,ToS
octet,and for
IPv6,Traffic
Class octet )
15432Bits:
CU
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