DSCP and Precedence Values

This section provides the DSCP and precedence values used in QoS class maps and policy maps.

Commonly Used DSCP Values

Unless noted as a restriction, you can mark both incoming and outgoing packets.

Table 6-1 lists the commonly used DSCP values described in RFC 2475.

 

Table 6-1 Commonly Used DSCP Values

DSCP Value
Decimal Value
Meaning
Drop Probability
Equivalent IP Precedence Value

101 110

46

High Priority

Expedited Forwarding (EF)

N/A

101 - Critical

000 000

0

Best Effort

N/A

000 - Routine

001 010

10

AF11

Low

001 - Priority

001 100

12

AF12

Medium

001 - Priority

001 110

14

AF13

High

001 - Priority

010 010

18

AF21

Low

010 - Immediate

010 100

20

AF22

Medium

010 - Immediate

010 110

22

AF23

High

010 - Immediate

011 010

26

AF31

Low

011 - Flash

011 100

28

AF32

Medium

011 - Flash

011 110

30

AF33

High

011 - Flash

100 010

34

AF41

Low

100 - Flash Override

100 100

36

AF42

Medium

100 - Flash Override

100 110

38

AF43

High

100 - Flash Override

001 000

8

CS1

 

1

010 000

16

CS2

 

2

011 000

24

CS3

 

3

100 000

32

CS4

 

4

101 000

40

CS5

 

5

110 000

48

CS6

 

6

111 000

56

CS7

 

7

000 000

0

Default

 

 

101 110

46

EF

 

 

IP Precedence Values

Table 6-2 lists the RFC 791 precedence values from least to most important.

 

Table 6-2 Precedence Values

Value
Description

000 (0)

Routine or Best Effort

001 (1)

Priority

010 (2)

Immediate

011 (3)

Flash - mainly used for Voice Signaling or for Video.

100 (4)

Flash Override

101 (5)

Critical -mainly used for Voice RTP.

110 (6)

Internet

111 (7)

Network