The network clerk when the computer system is connected to internet. He is receives and sends packets over internet and checks for damage during transmission. His inherent MAC number serves as the computer's unique identification number on internet.
A network interface controller (NIC), also commonly known as a network adapter, was an additional circuit board installed in early computers, just like a graphics card. Nowadays there are almost no computers that don't have internet access, so most NICs are made to be a chip on the motherboard and don't need to be installed separately.
Each NIC chip is assigned a unique Media Access Control Address (MAC Address) when it leaves the factory. This is a 6-byte number and although it is called an address, it is more like a unique ID number of the NIC chip or computer in the network world. If a computer has more than two NICs, such as wired and wireless, it will have more than two MAC addresses, which is not a problem.
What a NIC does is to receive or send a fixed-length data packet over a network connection, and the MAC addresses of the sender and the recipient are marked on the packet. On the Local Area Network (LAN) connected by the same cables, the packet will be circulated over the network cables. The recipient's NIC will pick the packet up when the marked recipient MAC addresses is its own MAC address, and will check whether the contents of the packet are incorrect due to the line quality. This simple mechanism can only be practiced within a LAN, but it is the basis of internet communication.
From LAN to Internet
Since the MAC address is only a number sequence that does not indicate the position of the computer using it, so internet has another address mechanism called "Internet Protocol (internet protocol, IP)". For each computer in internet, the local network manager assigns it a temporary "IP address (IP address)". An IP address consists of a large and smaller domain numbers, and the last host number, so it will be possible to know where the sender and receiver NICs of internet connection are located in the world, and then the data packets can be sent to the receiver's domain through a forwarding mechanism.
