The OSI model provides a method to deliver network traffic, not only to the system but to the application that requested or is listening for data.
Identity driven networking endeavors to resolve user and system based policy into a single management paradigm.
Before a user gets to the network there is usually some form of machine authentication, this probably verifies and configures the system for some basic level of access.
It is more usual for a user to attempt to authenticate once the system processes (daemons) are started, and this may well require the network configuration to have already been performed.
The first task when seeking to apply Identity Driven Network controls comprises some form of authentication, if not at the device level then further up the stack.