Understanding IP Protocol: Functions, IP Addresses, and Structure Explained

(1): What is the IP Protocol?

        The Internet Protocol (IP) is abbreviated as IP in English. In the OSI model, the IP protocol is located at the third layer, which is the network layer, and its main purpose is to enable communication between networks.

(2): What is an IP address? How is it generated?

        Internet Protocol Address is referred to in English as IP Address.

        Previously, we talked about the ARP protocol, and through analysis, it was found that it relies on the MAC address to send data. However, when ARP sends an ARP request through broadcasting, it needs to ensure that all hosts receive the packet. This not only lowers transmission efficiency but also confines it to the same subnet. That is to say, if two hosts are not in the same subnet, broadcast packets cannot be sent across. This design is reasonable; otherwise, it would lead to network-wide failure. Therefore, a method is needed to distinguish which MAC addresses belong to the same subnet, and which do not. For the same subnet, broadcasting is used, otherwise, “routing” is used. Hence, a new addressing system is introduced, known as the “IP” address, to allow users to distinguish whether different computers belong to the same subnet or not. A host thus has two types of addresses: a MAC address and an IP address, although they are not closely related. The MAC address is bound to the network card and is unique, whereas the IP address is assigned by a network administrator.

(3) IP Address

        An IP address is a unified address format provided by the IP protocol that assigns a logical address to each network and host on the internet, thereby masking the differences in physical addresses. IP addresses are divided into two main categories: IPv4 and IPv6, with IPv4 being most widely used. In IPv4, an IP address consists of 32 binary bits. As remembering a string of 32 binary bits is difficult for users, the IP address adopts a dot-decimal notation.

(4) Structure of an IP Address

          An IP address is divided into four separate parts because each IP address includes two parts: the network address and the host address. The network address identifies the LAN to which the device is connected, while the host address represents the devices within that LAN.

          However, it is usually difficult to judge the network portion with just an IP address alone. Hence, another parameter called the “subnet mask” is introduced. A subnet mask is also a 32-bit binary number. Its network portion is all ones, while the host portion is all zeros.

        For example: IP is 10.10.1.22, and its subnet mask is 11111111.11111111.00000000.00000000. This means the first half, 10.10, is the network address, and 1.22 is the host address.