The invention proposes a network device driver architecture with functionality distributed between kernel space and user space. The overall network device driver comprises a kernel-space device driver (10) and user-space device driver functionality (20). The kernel-space device driver (10) is adapted for enabling access to the user -space device driver functionality (20) via a kernel-space-user-space interface (15). The user-space device driver functionality (20) is adapted for enabling direct access between user space and the NIC (30) via a user-space-NIC interface (25), and also adapted for interconnecting the kernel-space-user-space interface (15) and the user-space-NIC interface (25) to provide integrated kernel -space access and user-space access to the NIC (30). The user-space device driver functionality (20) provides direct, zero-copy user-space access to the NIC, whereas information to be transferred between kernel space and the NIC will be "tunneled" through user space by combined use of the kernel-space device driver (10), the user-space device driver functionality (20) and the two associated interfaces (15,25).