Start learning network protocols

Is there any good way to learn a new knowledge to quickly master things in this field. After studying for so many years, it seems that there is no secret. However, this decision records the entire learning process for analysis and improvement.

First of all, the current level of understanding about the network is limited to the point of knowledge learned in the university, know what is a LAN, IP address, OSI Layer-7 model, TCP/IP is a de facto standard, and so on, however, it is not clear to go deeper. So where should we start learning. It seems that we recommend that you first read three volumes of classic TCP/IP books on the Internet. I have downloaded it, but it is difficult to watch it with my scalp. However, I cannot find a better method now. I will start with this.

Understand some concepts, such as TCP, UDP, MTU, and three-way handshakes. By studying these chapters, this is the basic requirement and purpose.