BERLIN — With the majority of Internet traffic expected to shift to congestion-prone mobile networks, there is growing debate on both sides of the Atlantic about whether operators of the networks should be allowed to treat Web users differently, based on the users’ consumption.

Proponents of the current system — called network neutrality — see that principle as a kind of civil rights declaration of the digital age, one that requires the gatekeepers of the global Internet to treat all users equally, regardless of application, source or download limit.

While operators have never been required to maintain neutrality, the industry has created that expectation largely by charging users a flat rate for unlimited Internet access.

But there is a big flaw in the concept, according to the operators: Networks have never been neutral. They have always been actively managed to some extent since their inception in the 1980s to ensure that all customers get a basic “best effort” level of service.