[seL4] How is network stack implemented in sel4

Hi, I have a few questions about network stack in sel4. Is network stack implemented in the kernel or user level? If in user level, are different protocols (IP/TCP) implemented in a single server or different servers? If in different servers, how do they communicate with each other? Is there any example code to show how to use network? How to send and receive TCP or UDP packets? How can I set up the network environment on bare metal machine? Is there documentation or instruction? Thanks a lot! Yuxin