L2 QOS - 802.1p Priority

This section will explain you about 802.1p priority field in L2 header.This field is majorly used in L2 QOS. 

      The 802.1p priority is located in the L2 packet header. It is used when you don’t want to analyze the L3 packet header, but need to ensure QOS in L2 environment. As shown in below diagram, the 4-byte 802.1Q header contains 2-byte TPID (Tag Protocol Identifier valued as 0x8100) and 2-byte TCI (Tag Control Information).

Figure 1 - Ethernet Frame with 802.1Q Header

The following figure shows the detailed contents of the 802.1Q header. Ethernet frame with 802.1Q header.

Figure 2 802.1Q header

As shown in above diagram, the Priority field in TCI is the 802.1p priority. It comprises three bits and the value range is 0-7.

It is called 802.1p priority.

Hope this information is informative for you. In coming post, I will share 802.1p configuration for L2 QOS.

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