ToS Byte

The TOS byte format is as follows:

The TOS byte is broken down into three components:

• Precedence—The most used component of the TOS byte, the precedence component is defined by three bits. There are eight possible precedence values ranging from 000 (decimal 0) through 111 (decimal 7). Generally, a precedence value of 000 refers to the lowest priority traffic, and a precedence value of 111 refers to the highest priority traffic.
• TOS—The TOS component is defined by four bits, although these bits are rarely used.
• MBZ—The must be zero (MBZ) component of the TOS byte is never used.