H3C Technologies H3C WX6000 Series Access Controllers - Manual (Page 431)

44-4
Figure 44-3 802.1Q tag headers
In the figure above, the 3-bit priority field in TCI is 802.1p precedence in the range of 0 to 7. In the figure
above, the priority field (three bits in length) in TCI is 802.1p precedence (also known as CoS
precedence), which ranges from 0 to 7.
Table 44-3 Description on 802.1p precedence
802.1p precedence (decimal) 802.1p precedence (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
The precedence is called 802.1p precedence because the related applications of this precedence are
defined in detail in the 802.1p specifications.
Traffic Policing and Line Rate Overview
If the traffic from users is not limited, a large amount of continuous burst packets will result in worse
network congestion. The traffic of users must be limited in order to make better use of the limited
network resources and provide better service for more users. For example, if a traffic flow obtains only
the resources committed to it within a certain period of time, network congestion due to excessive burst
traffic can be avoided.
Traffic policing is traffic control policies for limiting traffic and resource usage by supervising the traffic.
The prerequisite for traffic policing is to determine whether or not the traffic exceeds the set threshold.
Traffic control policies are adopted only when the traffic exceeds the set threshold. Generally, token
bucket is used for evaluating traffic.