Appendix B Packet Precedences; Ip Precedence And Dscp Values - HP A6600 Configuration Manual

Appendix B Packet precedences

IP precedence and DSCP values

Figure 47 ToS and DS fields
Bits: 0
Preced
IPv4 ToS
ence
byte
RFC 1122
IP Type of Service (ToS)
As shown in Figure
IP precedence from 0 to 7. According to RFC 2474, the ToS field is redefined as the 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 6 Description on IP precedence
IP precedence (decimal)
0
1
2
3
4
5
6
7
1 2 3 4 5 6 7
M
Type of
B DS-Field
Service
Z
(for IPv4,ToS
octet,and for
IPv6,Traffic
Class octet )
Must
RFC 1349
Be
Zero
RFC 791
47, the ToS field in the IP header contains eight bits. The first three bits (0 to 2) represent
IP precedence (binary)
000
001
010
011
100
101
110
111
Bits: 0 1 2 3 4 5 6
DSCP
CU
Class Selector Currently
codepoints Unused
Differentiated Services
Codepoint (DSCP)
RFC 2474
138
7
Description
Routine
priority
immediate
flash
flash-override
critical
internet
network