learning target:
Penetration Testing Project
Learning Content:
1 Understand what internal and external networks are
2. Understand what is an IP address
3. Understand the OSI seven-layer model and the TCP/IP five-layer model
4. Understand the difference between TCP and UDP
Internet and IP address:
Internet overview: The
Internet is a collection of global information resources. There is a rough saying that INTERNET is a logical network formed by the interconnection of many small networks (subnets), and several computers (hosts) are connected to each subnet.
The Internet aims to exchange information resources with each other. It is based on some common protocols and is formed by many routers and public Internet. It is a collection of information resources and resource sharing.
The relationship between local area network, metropolitan area network and wide area network:!
[Insert picture description here](https://img-blog.csdnimg.cn/20201113144209560
IP address: The
IP address is a 32-bit binary number, usually divided into 4 "8-bit binary numbers" (that is, 4 bytes). The IP address is usually expressed in "dotted decimal notation" in the form of (abcd), where a, b, c, and d are all decimal integers between 0 and 255. Example: The dotted decimal IP address (100.4.5.6) is actually a 32-bit binary number (01100100.00000100.00000101.00000110).
OSI seven-layer model
Concept
OSI (open system Interconnect), that is, open system interconnection. It is generally called the OSI reference model, which is a network interconnection model researched by the ISO (International Organization for Standardization) organization in 1985.
In order to better make network applications more popular, ISO has introduced the OSI reference model. The implication is that it is recommended that all companies use this specification to control the network. In this way, all companies have the same specifications and can be interconnected.
Common application layer protocols: