3Com S7902E, Configuration Manual

Page: 1809 / 2621

13-10
As shown in Figure 13-1 , 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 13-20 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
7 111 network
Table 13-21 Description on DSCP values
DSCP value (decimal) DSCP value (binary) Description
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
30 011110 af33
34 100010 af41
36 100100 af42
38 100110 af43
8 001000 cs1
16 010000 cs2
24 011000 cs3
32 100000 cs4
40 101000 cs5
48 110000 cs6
56 111000 cs7