Shulou(Shulou.com)06/02 Report--

Key points:

1. Overview and basic Concepts of computer Network

two。 Hierarchical model

3. Data transmission process

one。 Overview and basic concepts of computer network:

(1) Theory:

1. What is a computer network:

1) what is a computer network:

Hardware: connect network devices to computers through cables

Software: operating system, application software, application programs are interconnected through communication lines

Realize resource sharing and information transmission.

2) the functions of computer network: data communication; resource sharing; increase reliability; improve system processing capacity.

3) the development of the Internet in China (read the following websites and documents):

Http://www.cnnic.cn/ (China Internet Information Center) view

Http://www.cnnic.cn/hlwfzyj/hlwxzbg/ (download the latest report)

The 41st Statistical report on the Development of the Internet in China. Pdf (763 million netizens)

Evaluation report on National Informatization Development. Pdf

4) computer network development:

5) protocols and standards:

Three elements of protocol: syntax, semantics and synchronization

A standard is an agreed agreement, a well-known organization that specifies a standard:

ISO (International Organization for Standardization)

ANSI (U.S. National Bureau of Standardization)

ITU-T (International Telecommunication Union-Telecommunication Standards Department)

IEEE (Institute of Electrical and Electronic Engineers)

2.WAN and LAN:

1) WAN: wide area network

Range: tens to thousands of kilometers

Function: for connection

Long-distance computer network

Typical application: Internet

2) LAN: local area network

Range: around 1km

Function: for short connection

Computer within distance

Typical applications: enterprise network, campus network

3.IEEE 802 LAN standard:

1) IEEE 802.3: limited LAN standard

IEEE 802.3u standard, 100 megabit fast Ethernet standard

IEEE 802.3z standard, fiber optic media implementation Gigabit Ethernet standard specification

IEEE 802.3ab standard, twisted pair implementation Gigabit Ethernet standard specification

IEEE 802.3ae standard to implement 10 Gigabit Ethernet standard

IEEE 802.3ba standard, implementing 100000 Ethernet standard

2) IEEE 802.11: wireless LAN standard

IEEE 802.11a with rates up to 54Mbps

IEEE 802.11b with rates up to 11Mbps

IEEE 802.11g with rates up to 54Mbps

IEEE 802.11n with rates up to 600Mbps

4. Common network devices:

1) switching routing equipment

2) Network security devices: firewalls, × × devices

3) Wireless network equipment

4) Network equipment manufacturers: Cisco (Cisco), Huawei, H3C, juniper, D-link)

Please open from Baidu encyclopedia to understand the above companies, the interview is very useful, you can make money!

5. The most basic network:

1) the most basic network: PC (computer)-- > switch-- > router-- > firewall-- > public network.

2) illustrating the basic network:

two。 Hierarchical model:

(1) Theory:

1. Hierarchical idea and OSI reference model:

The core theory of hierarchical thought: decompose the complex process into several sub-processes with relatively single function; the whole process is clearer and complex problems are simplified; it is easier to find problems and solve problems.

1) people who enjoy milk may not know the production process:

2) people who use the network may not know the process of data transmission:

3) the International Organization for Standardization (International Standard Organization,ISO) promulgated the Open Systems Interconnection (Open System Interconnection,OSI) reference model in 1984; the OSI reference model is an open architecture, which stipulates that the network is divided into seven layers: physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer.

2.OSI seven-layer model, TCP/IP four-layer model, TCP/IP five-layer model:

1) the five layers of TCP/IP are the upper three layers of the OSI seven-layer model (the table will be) turned into the application layer:

2) composition of TCP/IP protocol family:

three。 Data transfer process:

(1) Theory:

1. Data encapsulation process:

The process of data encapsulation is to add the head of that layer to the first layer:

two。 Data unencapsulation process:

In the data unencapsulation process, the header of the layer is removed from the first layer:

The relationship between 3.PDU (Protocol data Unit) and TCP/IP:

1) PDU (Protocol data Unit): is the name of the data transferred at this layer.

2) the corresponding relationship between device and layer:

3) Communication between layers:

The characteristic is that each layer on different nodes only recognizes this layer protocol:

If you understand the picture below, you can understand how the data on the network is transmitted. Work hard!

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