1p priority – H3C Technologies H3C S12500 Series Switches User Manual

Page 94

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85

DSCP value (decimal)

DSCP value (binary)

Description

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)

802.1p priority

802.1p priority lies in the Layer 2 header and applies to occasions where Layer 3 header analysis is not

needed and QoS must be assured at Layer 2.

Figure 21 An Ethernet frame with an 802.1Q tag header

As shown in

Figure 21

, the 4-byte 802.1Q tag header consists of the tag protocol identifier (TPID, 2 bytes

in length), whose value is 0x8100, and the tag control information (TCI, 2 bytes in length).

Figure 22

shows the format of the 802.1Q tag header. The Priority field in the 802.1Q tag header is called the
"802.1p priority", because its use is defined in IEEE 802.1p.

Table 17

shows the values for 802.1p

priority.

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