∙Assured forwarding (AF) class: This class is divided into four subclasses (AF 1 to AF 4), each containing three drop priorities for more granular classification. The QoS level of the AF class is lower than that of the EF class.

∙Class selector (CS) class: This class is derived from the IP ToS field and includes eight subclasses;

∙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. All IP network traffic belongs to this class by default.

3.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

 

 

 

0

000000

be (default)

 

 

 

Table 151 802.1p precedence

802.1p precedence lies in Layer 2 packet headers and is applicable to occasions where Layer 3 header analysis is not needed and QoS must be assured at Layer 2.

b.An Ethernet frame with an 802.1Q tag header

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