One way PERMANENT links only. No link exchanges.

我要的是一个永久的链接方式，而不是交换链接。

youdao

Rather, they estimate that only one in four of the attackers has links to the insurgents in one way or another, with only one in ten attacks being the work of infiltrators.

ECONOMIST: The war in Afghanistan

And one way of looking at such links is the Network Rail view that it only makes financial sense when you've built 400 miles of it, because that's when savings from journey times compete with air links.

BBC: Making tracks and political points