H3C S3100-52P Operation Manual page 546

Operation Manual – QoS-QoS Profile
H3C S3100-52P Ethernet Switch
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 1-3 An Ethernet frame with an 802.1Q tag header
As shown in the figure above, 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).
802.1Q tag header.
Figure 1-4 802.1Q tag headers
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 1-4 Description on 802.1p priority
802.1p priority (decimal)
0
1
2
3
4
5
6
7
The precedence is called 802.1p priority because the related applications of this
precedence are defined in detail in the 802.1p specifications.
Figure 1-4 describes the detailed contents of an
802.1p priority (binary)
000
001
010
011
100
101
110
111
1-8
Chapter 1 QoS Configuration
Description
best-effort
background
spare
excellent-effort
controlled-load
video
voice
network-management