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AR Router Troubleshooting Guide

This Product Documentation provides guidance for maintaining AR Enterprise Router, covering common information collection and fault diagnostic commands, typical fault troubleshooting guide, and troubleshooting.
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Are CoS Values 0-7 of the 802.1P Protocol in Descending Order of Priority?

Are CoS Values 0-7 of the 802.1P Protocol in Descending Order of Priority?

802.1P is one of IEEE 802.1 protocols, and defines the priority (CoS value) of Ethernet frames. 802.1Q that defines VLAN information in Ethernet frames was also released with 802.1P. 802.1P and 802.1Q are often used together. They add a tag composed of 12-bit VLAN information and 3-bit CoS information to the Ethernet frame header.

When performing Layer 2 switching, an Ethernet switch use CoS values to differentiate priorities of Ethernet frames. When DiffServ is used, a Layer 3 switch or an edge router is often configured to map CoS values to ToS values in IP headers to achieve QoS guarantee. A ToS value identifies the priority of an IP packet.

CoS values 0-7 defined in 802.1P are in descending order of priority. The default value 0 is not the lowest to ensure compatibility.

CoS values 0-7 are as follows:


7(highest) management


4.............controlled load

3.............excellent effort



0(default) effort

Updated: 2019-05-10

Document ID: EDOC1000079719

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