3Com 4200G 12-Port Configuration Manual page 362

Best Effort (BE) class: This class is a special CS class that does not provide any assurance. AF
traffic exceeding the limit is degraded to the BE class. Currently, all IP network traffic belongs to
this class by default.
Table 1-3 Description on DSCP values
DSCP value (decimal)
46
10
12
14
18
20
22
26
28
30
34
36
38
8
16
24
32
40
48
56
0
2) 802.1p precedence
802.1p precedence lies in Layer 2 packet headers and is applicable to occasions where Layer 3 packet
analysis is not needed and QoS must be assured at Layer 2.
Figure 1-3 An Ethernet frame with an 802.1q tag header
As shown in Figure 1-3, each host supporting the 802.1q protocol adds a 4-byte 802.1q tag header after
the source address field of the former Ethernet frame header when sending packets.
DSCP value (binary)
101110
001010
001100
001110
010010
010100
010110
011010
011100
011110
100010
100100
100110
001000
010000
011000
100000
101000
110000
111000
000000
1-5
Description
ef
af11
af12
af13
af21
af22
af23
af31
af32
af33
af41
af42
af43
cs1
cs2
cs3
cs4
cs5
cs6
cs7
be (default)