Why Is a Network Tunnel Called a “Tunnel”?

The terminology one encounters when getting into the computing world may seem odd or leave you puzzled at times, wondering how and why these terms are in use. With that in mind, today’s SuperUser Q&A post has the answers to a confused reader’s questions.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

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The Question

SuperUser reader user7681202 wants to know why a network tunnel is called a “tunnel”:

I do not understand why the “tunnel” metaphor is used to describe a networking tunnel.

At first, I thought the reason was because the data was sent in an encrypted form so that an eavesdropper would not be able to see the data (seeing the data wrapped in a tunnel instead).

But what of the tunneling protocols that do not use encryption? Why are they also called “tunnels”?

Why is a network tunnel called a “tunnel”?

The Answer

SuperUser contributors Mokubai and DavidPostill have the answer for us. First up, Mokubai:

In the case of roads, a real world tunnel is a constructed passage that allows you to pass directly from point A to point…

Sasha Harriet

Sasha Harriet

As content editor, I get to do what I love everyday. Tweet, share and promote the best content our tools find on a daily basis.

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Sasha Harriet

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