1. NETWORKS

2. Definition
A combination of hardware and software that allows computers to exchange data and share software and devices, such as printers.

3. Networks are widely used because:
Allows users to reliably share and exchange data
Can reduce costs by sharing devices such as printers
Offers security options including password protection to restrict access to certain files
Simplifies file management through centralized software updates and file backups
Provides for network users

4. Networks are classified by:
Size (LAN, WAN, MAN, HAN)
Architecture (peer-to-peer, client/server)
Topology (refers to arrangement of nodes on the network)

5. Transmission Media
Computers must be connected in order to transmit data between nodes. Cable transmission media includes twisted-pair wiring, coaxial cable, and fiber optic cable. Wireless transmission media includes infrared signals, broadcast radio, cellular radio, microwaves, and communication satellites.

6. Bandwidth
The amount of data and the speed at which data can travel over a media is called bandwidth, which is measured in bits per second(bps).

7. Peer-to-Peer Architecture
Each computer on the network is considered equal in terms of responsibilities and resource sharing.

8. Client/Server Architecture
Network consists of a group of computers, called clients, connected to a server. A server is a computer with more RAM, a larger hard disk, and sometimes multiple CPUs that is used to manage network functions.

9. Bus Topology
A physical LAN topology that uses a single central cable, called the bus or backbone to attach each node directly.

10. Star Topology
Each node is attached to a hub, which is a device that joins communication lines at a central location on the network.

11. Ring Topology
Each node is connected to form a closed loop. A LAN with a ring topology can usually cover a greater distance than a bus or star topology

12. Different nets
Intranet – a network that is used by a single organization. The purpose of an intranet is to share information.
Extranet – extends an intranet by providing various levels of accessibility to authorized members of the public.
Internet – the largest and most widely accessed network, a world-wide network of computers that is not controlled by any one organization.

13. Internet
Numerous networks all linked together through routers. A router is a device that connects different network technologies. Networks connected to routers use TCP/IP (Transmission Control Protocol / Internet Protocol) software to communicate.

14. Telecommunications
Conventional modem – uses standard telephone lines to convert analog signals to digital data. 56 kbps
DSL (Digital Subscriber Line) – uses a standard telephone lines with transmissions up to 640 kbps.
Cable modem – transmits data through coaxial cable television network. 2 mbps – 10 mbps
Leased/Dedicated lines – permanent connection to the Internet that is always active. A T-1 carrier is a type of leased line that transmits data at mbps
ISDN (Integrated Services Digital Network) – is a digital telephone network provided by a local phone company. 64 kbps

15. Common Terms Firewall Blog Spam Boolean logic Spyware IP address
Encryption
Virus
Trojan Horse
Worm
Antivirus programs
Crackers,Hackers
Phishing
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