H3C S5120-EI Series Operation Manual page 557

DSCP value (decimal)
56
0
2) 802.1p priority
802.1p priority lies in Layer 2 packet headers and is applicable to occasions where the Layer 3 packet
header does not need analysis but QoS must be assured at Layer 2.
Figure 3-2 An Ethernet frame with an 802.1Q tag header
As shown in Figure 3-2, the 4-byte 802.1Q tag header contains a 2-byte Tag Protocol Identifier (TPID)
whose value is 8100 and a 2-byte Tag Control Information (TCI). TPID is a new class defined by IEEE to
indicate a packet with an 802.1Q tag.
header.
Figure 3-3 802.1Q tag header
In the figure above, the 3-bit priority field in TCI is 802.1p priority in the range of 0 to 7. In the figure
above, the priority field (three bits in length) in TCI is 802.1p priority (also known as CoS precedence),
which ranges from 0 to 7.
Table 3-3 Description on 802.1p priority
802.1p priority (decimal)
0
1
2
3
4
5
6
7
DSCP value (binary)
111000
000000
Figure 3-3 describes the detailed contents of an 802.1Q tag
802.1p priority (binary)
000
001
010
011
100
101
110
111
3-3
Description
cs7
be (default)
Description
best-effort
background
spare
excellent-effort
controlled-load
video
voice
network-management