Computer network addressing: In real life, when we express things to a friend’s house, we first need to know the specific address of his house to the house number. Similarly, in the computer network communication address, there is also an address structure. Specifically, point-to-point, we can use the computer network address structure to communicate with the postal service. The structure of the address is understood by comparison: the network address is imagined as the name of the city and the street; the physical address is likened to the house number, and the port address is very similar to which person under the same house receives the letter.
IP Addressing
Computer network addressing: It is the IP address that identifies which network the target host is on. IP addresses are represented by four dotted decimal numbers, such as 172.155.32.120. It’s just that the IP address is a composite address, and it is the address of a host in its entirety. Only look at the first half, indicating the network address. The address 172.155.32.120 represents the address of a host, and 172.155.0.0 represents the network address of the network where the host is located.
The IP address is encapsulated in the IP header of the datagram. IP addresses serve two purposes: routers on the network use the IP addresses to determine the destination network address and then determine which port to forward packets to. Another use is that the source host uses the IP address of the target host to query the physical address of the target host.
MAC Addressing
Computer network addressing: The physical address is encapsulated in the frame header of the datagram. A typical physical address is the MAC address in Ethernet. The MAC address is used in two places: the network card in the host determines. Whether the datagram sent by the network is sent to itself through the destination MAC address in the header; the switch in the network uses the destination MAC address in the header to determine the destination of the datagram. Which port to forward. Examples of other physical addresses are the DLCI address in Frame Relay networks and the SPID in ISDN.
The port address is encapsulated in the datagram’s TCP header or UDP header. The port address is the source host telling the destination host which application the datagram is sand to. If the target port address in the TCP header indicates. 80 it indicates that the data is sent to the WWW service program; if it is 25130, it is sent to the CS game program of the opposite host.
Computer networks rely on the joint addressing of network addresses, physical addresses, and port addresses to complete data transmission. Without any of these addresses, the network cannot complete addressing. (The communication of point-to-point connection is an exception. In point-to-point communication. Two hosts are directly connect with a physical line, and the data sent by the source host will only reach the other host along this physical line, and the physical address is not necessary.)
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