2-Network Overview

First, the network model

OSI layer Seven model: application layer, presentation layer, session layer, Transport layer, network layer, data link layer, physical layer

OSI Four layer Model: application layer, Transport layer, network layer, network interface layer

TCP/IP Five Layer model: application layer, Transport layer, network layer, data link layer, physical layer

II. Basic overview of computer networks

1. Hardware: Connecting network devices and computers via cables

2, Software: Operating system, application software, applications through the communication line interconnection

3, the realization of resource sharing, information transmission

Third, the function of computer network

Data communication, resource sharing, increasing reliability and improving system processing ability

Iv. Development of computer networks

First ARPANET packet switching

Second nfsnet TCP/IP

Third Browser Mosai Web technology

V. Network protocols and standards

1, protocol: A group of control data communication rules, the three elements of the Protocol: syntax, semantics, synchronization

2, Standard: IOS (International Organization for Standardization) created the OSI (Open Systems Interconnect) model in network communication

ANSI (National Bureau of Standardization)

ITU-T (International Telecommunication Union-Telecommunication Standards) IEEE (Association of Electrical and Electronics Engineers)

3. IEEE802 LAN Standard

1>ieee802.3 (wired LAN Standard)

IEEE 802.3AB Standard, twisted pair for Gigabit Ethernet standard Specification

IEEE 802.3an twisted-pair million gigabit

IEEE 802.3z Fibre Gigabit

IEEE 802.3ae Fiber million gigabit

IEEE 802.3u Gigabit Fast Ethernet Standard

2>ieee802.11 (Wireless LAN standard)

ieee802.11a 5GHZ 54Mbps

IEEE802.11B 2.4GHZ 11Mbps

ieee802.11g 2.4GHZ 54Mbps

IEEE802.11N is a standard that is also widely used in the draft stage, up to 600Mbps, compatible with WLAN and the integration of WAN (for example: 4G business)

Vi. WAN and LAN

Wan: Wide-area network for long-distance networks typical applications: Internet

LAN: LAN for connecting short, near-distance computers, typical applications: Enterprise network, Campus Network

Seven, network equipment

Switches, routers

Network security devices: Firewalls, VPN devices

Wireless network devices: Wireless LAN, wireless router, AP

Eight, network topology structure:

1. Star-shaped topology:

Advantages: Easy to implement, easy to network expansion, easy to troubleshoot

Disadvantage: central node pressure is high, networking cost is higher

2. Network topology: Each node is connected with at least two other nodes, high reliability, high cost of networking

3. Total linear topology

Ix. conversion of the binary system

Ten, the amount of storage

Computer storage available bit and byte metering: 8 bits = 1 bytes 1000 bytes =1kb 1000kb= 1MB ....

2-Network Overview