(In 2017, teacher Han Ligang published the book "Innovative Course of Computer Network Principles" supporting PPT. In the period, there are teacher Han Ligang QQ number 458717185 and WeChat account hanligangdongqing. If you have problems in learning computer network principles, you need the software and documents required for the course, you can contact teacher Han Ligang to ask for it. .
Chapter 4 Data Link Layer v2.pptx)