Computer network diagnostics: basic protocols (1)

During the time when I started network debugging, I always wanted to figure out how LAN access to the Internet was. Now pay attention to your computer. After the boot, after dozens of seconds of waiting, the operating system interface on the screen will appear in front of us. Just click on the browser icon to access our favorite website. However, nothing appears on the webpage as you think. What's wrong? Don't worry. We will handle this problem as soon as possible. On any operating system, we can fix it with network diagnostic software.

But the first thing we need to know is how you access the network?

This problem seems trivial, but it usually takes a long time for no response. Whenever we ask the computer to use the network, we mean any adapter or cable, and sometimes a router is needed. Of course, these things are very important to the use of computer networks, but they do not allow user access. To effectively use computer networks, our service specifications must be installed in the network protocols of any computer.

Of course, there are some different solutions for different networks. The simplest one is the TCP/IP protocol that has been installed by default on our computer and has a permanently assigned IP address, which is an eternal brand in the local configuration settings. This is the simplest solution we can access, but it is not actually safe, so we assume that the Administrator has made some other settings.

Most likely, your DHCP server has been started by the Administrator. This service allows any workstation on the network to dynamically allocate IP addresses. There is usually a private IP address in the local network, which is not visible on the Internet. We can only see the vro network IP address. The real purpose of a translation task is to access the private address through appropriate responses and obtain the content on the screen. These are what we really need. Sometimes the Administrator has some reason to install an old internet protocol. In fact, the gateway is used to package data in the network. It is responsible for the translation of relevant network protocol data.

If we use a solution based on an internal network VPC address that will never be found on the Internet, this solution is called the network address translation technology, which is abbreviated as NAT. There are also multiple types of networks based on NAT technology. I divide NAT into static, dynamic, active, passive, positive, and negative. Maybe someone else is different from me, but you have to admit that NAT itself is fascinating. The NAT workflow is as follows: a packet is transmitted to an internal network interface, which contains the address of our workstation. It takes the address in our private address pool, then, the router is routed to an external interface, where the network interface address is located. The real answer is that it is always redirected to what you need.

Private addresses are much more common than public addresses. Then, we have to deal with a lot of private addresses and a public address. In addition, in order to clarify the Addressing response of the server and connect a set of suitable internal ports to external port addresses, We need to allocate each address. There is a protocol that can provide dynamic ports for us from the pool. This technology that changes the data port is called PAT.

You may have noticed that all addresses from the internal network cannot be real addresses, but it is a good way to keep the addresses in the private address pool. This has many benefits, which protects private networks. Fortunately, there are some wonderful Methods everywhere, whether it's Network Address Allocation, testing, or software development. Sometimes some network conversion operations may also occur on the third and fourth layers of the entire ISO/OSI model. The IP address of the data packet does not change, but it is still between the fourth layer protocols. This solution is called the circuit layer proxy.

If you look at most networks, you will find some similarities that are visible to the naked eye. Most of the time, administrators can use the same private IP network. To solve Network conflicts, all computer addresses are dynamically allocated. The Dynamic Address allocation process can be completed by multiple protocols, but the most important of them is the DHCP service. This provides unlimited potential for transmitting information to specific workstations. DHCP not only provides information about the IP address data of the workstation, but also contains information about the gateway address. It has a wide range of information, such as the data network and server content.