The interconnection protocol between networks is also a protocol designed for computer networks to communicate with each other. In the internet, it is a set of rules that can make all computer networks connected with the internet communicate with each other, and stipulates the rules that computers should abide by when communicating on the internet. As long as it conforms to the IP protocol, any computer system produced by any manufacturer can be interconnected with the Internet. IP addresses are unique and can be divided into five categories according to the nature of users. In addition, IP also has the meanings of entrance protection, intellectual property, pointer register and so on.
The IP address is a 32-bit binary address. Theoretically, there are about 4 billion possible address combinations (2 to the 32nd power), which seems to be a large address space. Actually, according to the law of different digits of network ID and host ID, IP addresses can be divided into three categories: A (7-digit network ID and 24-digit host ID), B (14-digit network ID and 16-digit host ID) and C (2 1 digit network ID and 8-digit host ID). Due to historical reasons and technical development differences, class A addresses and class B addresses. So IP address is a very important network resource.
For organizations with Internet services, because their hosts have opened access services such as WWW, FTP and E-mail, it is usually necessary to publish a fixed IP address to facilitate users' access. Of course, digital IP is not easy to remember and identify, and people are more accustomed to accessing hosts through domain names, and domain names still need to be translated into IP addresses through DNS. For example, your homepage address is easy for users to remember and use, and the domain name server will translate this domain name into101.12.123.234, which is your real address on the Internet.
For most dial-up users, it is not advisable to assign a fixed IP address (static IP) to each user because the time and space of surfing the Internet are discrete, which will cause great waste of IP address resources. Therefore, these users usually get a dynamic IP address automatically every time they call the ISP's host. Of course, this address is not arbitrary, but an address within the legal range of the network ID and host ID applied by the ISP. Dial-up users' IP addresses are likely to be different at any two connections, but the IP addresses remain the same during each connection.