O que é Network interface card, Ethernet frame?

A network interface card (NIC) is the device that connects a computer to a network link: it turns the bits on the wire into data in the host’s memory and back. An Ethernet frame is the unit an Ethernet link carries: a destination and a source address (6 bytes each), a type (2 bytes), a payload of 46 to 1 500 bytes and a frame check sequence (4 bytes), from 64 to 1 518 bytes in all without a VLAN tag. On the wire each frame is preceded by 8 bytes of preamble and start delimiter and followed by at least 12 bytes of idle inter-frame gap.