tion
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 Layer 2 packet headers and applies to situations where Layer 3 header analysis is
not needed and QoS must be assured at Layer 2.
Figure 479 An Ethernet frame with an 802.1Q tag header
As shown in Figure 479, the 4-byte 802.1Q tag header consists of the tag protocol identifier (TPID, two
bytes in length), whose value is 0x8100, and the tag control information (TCI, two bytes in length). Figure
48
0 shows the format of the 802.1Q tag header. The priority in the 802.1Q tag header is called "802.1p
priority," because its use is defined in IEEE 802.1p. Table 145 pr
esents the values for 802.1p priority.
Figure 480 802.1Q tag header
1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 Priority VLAN ID
TPID (Tag protocol identifier) TCI (Tag control information)
Byte 1 Byte 2
0
Byte 3 Byte 4
CFI
7 5432107 5432106 6 7 5432107 54321066
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