socket

1.         construct the bsd socket data structure, noted that there is no /dev/eth0 exists

2.         write system call will finally put the user datagram from socket buffer into NIC’s sending queue

3.         the copying from sending queue to NIC’s device memory ( data send activity ) is done by soft irq

4.         after data sent, an interruption is triggered, the results will be checked

5.         read much like write with a reversed direction, finally the payload will be copied to the socket buffer