7-3
called the 802.1p priority, because its use is defined in IEEE 802.1p.
presents the values for
802.1p priority.
Figure 7-3
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
5 4 3 2 1 0 7
5 4 3 2 1 0
6
6
7
5 4 3 2 1 0 7
5 4 3 2 1 0
6
6
Table 7-3
Description on 802.1p priority
802.1p priority (decimal)
802.1p priority (binary)
Description
0 000
best-effort
1 001
background
2 010
spare
3 011
excellent-effort
4 100
controlled-load
5 101
video
6 110
voice
7 111
network-management
802.11e Priority
To provide QoS services on WLAN, the 802.11e standard was developed. IEEE 802.11e is a MAC-layer
enhancement to IEEE 802.11. IEEE 802.11e adds a 2-byte QoS Control field to the 802.11e MAC frame
header. Three bits of the QoS control field represents the 802.11e priority, which ranges from 0 to 7.
Figure 7-4
802.11e frame structure
Priority Mapping Overview
Introduction to Priority Mapping
When a packet enters an AP, the AP assigns a set of QoS priority parameters to the packet based on a
certain priority field carried in the packet and sometimes may modify its priority, according to certain
