The Virtual Interface Architecture (VIA) is an abstract model of a user-level zero-copy network, and is the basis for InfiniBand, iWARP and RoCE.
In the same school of thought, a virtual network interface protected across process boundaries could be accessed at the user level.
Another facet of traditional networks is that arriving data is placed in a pre-allocated buffer and then copied to the user-specified final destination.
There is no intermediary copying and all of these actions occur without the involvement of the CPUs, which has an added benefit of lower CPU utilization.
To ensure that only the process that owns the registered memory may access it, the VIA NICs require permission keys known as "protection tags" during communication.