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12-6
Table 12-3
The default
dscp-lp
,
dscp-dp
,
dscp-dot1p
, and
dscp-exp
priority mapping tables
Input priority value dscp-dp mapping dscp-dot1p mapping
DSCP Drop precedence (dp) 802.1p priority (dot1p)
0 to 7 0 0
8 to 15 0 1
16 to 23 0 2
24 to 31 0 3
32 to 39 0 4
40 to 47 0 5
48 to 55 0 6
56 to 63 0 7
Appendix C Introduction to Packet Precedences
IP Precedence and DSCP Values
Figure 12-1
ToS and DS fields
As shown in
Figure 12-1 , the ToS field of the IP header contains eight bits, and the first three 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 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 12-4
Description on 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