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5-4-3 Rule

What Does 5-4-3 Rule Mean?

The 5-4-3 rule is a guideline used in the design of shared Ethernet networks which promotes optimal traffic flow. This refers to the number of repeaters and segments that must be present on shared Ethernet backbones set up in a tree topology. The rule states that there should be a maximum of five segments which are connected by four repeaters, and only three of those segments can contain active senders/terminals.


Techopedia Explains 5-4-3 Rule

The Ethernet protocol dictates that data sent over the collision domain must reach every part on its path toward its destination within a specified length of time. However, each repeater and segment that the signal passes through adds a certain amount of time in the process. The rule was created in the early days of the Ethernet when 10Base5 and 10Base2 were the only Ethernet types available, and shared access backbones were quite slow. The 5-4-3 rule was designed to minimize signal transmission time.


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