Network Technology and Application Study Notes-Overview of Computer Network Basics

I. Concept of Computer Network

What is computer network?

A computer network connects multiple computers distributed in different geographical locations and operated independently using communication devices or lines, A fully functional network software (such as network protocols, information exchange methods, and network operating systems) can be used to share network resources and transmit information. Such a system can be called a computer network.

You can alsoHardware and softwareIt can be understood from two aspects:

Hardware: Connect network devices (routers, switches, and firewalls) to computers through cables (Network cables, optical fiber cables, and wireless signals ).

Software: The operating system, application software, and applications can communicate with each other through communication lines to achieve resource sharing and information transmission.

2. Functions of computer networks

The main functions of computer networks include the following:

1. Data Communication

2. Resource Sharing

3. Increased reliability

4. Improve system processing capability

 

Iii. Brief History of Computer Network Development

1,The first phase (20Century 60Times)

Iconic event: apranet

Key technologies:Group exchange

 

2Stage 2 (20Century 70End-80(Early)

Landmark event: NSFnet

Key technologies:TCP/IPImplementation

 

3Stage 3 (20Century 90Mid-term)

Iconic event: mosai Browser

Critical events:WebTechnology

Iv. network protocols and standards

1, Protocol

The protocol can be understood as a "rule", while the standard can be understood as a "rule of unanimous consent"

A protocol is a set of rules that control data communication. It defines what needs to be transmitted between network nodes, how to communicate, and when to communicate. This is the three elements of the Protocol:Syntax, semantics, and Synchronization

2, Standard

ISO (International Standardization Organization)

ANSI (US International Standardization Bureau)

ITU-T (ITU-Telecommunications Standards Department)

IEEE (Institute of Electrical and Electronics Engineers)

 

5. IEEE 802LAN Standard

WanAnd lanDifference:

Wan (WAN)

Range: dozens to thousands of meters

Role: used to connect to a remote computer network

Typical application: Internet

Lan)

Value range: About 1km.

Role: used to connect to a short Computer Network

Typical applications: Campus Network and Enterprise Network

1, IEEE 802.3

IEEE 802.3u standard and MB Fast Ethernet standard

IEEE 802.3z standard, optical fiber media standard for Gigabit Ethernet

IEEE 802.3ab standard, twisted pair wires implement Gigabit Ethernet standard specifications

IEEE 802.3ae standard, optical fiber media standard for 10 Gigabit Ethernet

IEEE 802.3an standard, twisted pair wires enable 10 Gigabit Ethernet standard specifications

2, IEEE 802.11

IEEE 802.11a, with a carrier frequency of 5 GHz and a communication rate of up to 54 MB/S

IEEE 802.11b, with a carrier frequency of 2.4 GHz and a communication rate of up to 11 MB/S

IEEE 802.11q, with a carrier frequency of 2.4 GHz and a communication rate of up to 54 MB/S

IEEE 802.11n

Vi. Common network devices

Common network communication devices include:Exchange routing devices, network security devices, wireless network devices, etc.

1Switch routing device

Vro: Cisco 2800 series, Cisco 2621, Cisco 3725, Cisco 3640

Vswitch: Cisco 3560, Cisco 3750, and Huawei 9306 Switches

2Network Security Device

Firewall:Attackers can defend against attacks from the company's internal and external networks.

Cisco ASA 5505, 5510, 5520, 5540, 5550, 5580

VPNDevice:Virtual Private channel through the Internet

3And wireless network devices:Wireless Router (TP-LINK), wireless network card, Wireless Bridge

4Network device manufacturer:CiscoCompanies, Huawei companies

Vi. Network Topology

1) Star-based topology

Advantages:

1. Easy to implement

2. Easy network expansion

3. Easy troubleshooting

Disadvantages:

1. High pressure on the central node

2. Easy to form a single point of failure

2) network topology:

Each node must be connected to at least two other nodes.

High reliability and high networking cost

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Network Technology and Application Study Notes-Overview of Computer Network Basics