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A collection of computer and devices connected together via communication device and transmission media to share resources
(Shelly,2018)

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•The process in which two or more computer or devices transfer data, instruction and information

•Some communication involve cables and wires; other are sent wirelessly through the air

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*HARDWARE

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A communications device is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device. One type of communications device that connects a communications channel to a sending or receiving device such as a com- puter is a modem. Computers process data as digital signals. Data, instructions, and information travel along a communications channel in either analog or digital form, depending on the com- munications channel. An analog signal consists of a continuous electrical wave. A digital signal consists of individual electrical pulses that represent bits grouped together into bytes.

For communications channels that use digital signals (such as cable television lines), the modem transfers the digital signals between the computer and the communications channel. If a communications channel uses analog signals (such as some telephone lines), however, the modem first converts between analog and digital signals.

The following pages describe the following types of communications devices: dial-up modems, ISDN and DSL modems, cable modems, wireless modems, network cards, wireless access points, and routers.

Dial-Up Modems

As previously discussed, a computer's digital signals must be converted to analog signals before they are transmitted over standard telephone lines. The communications device that performs this conversion is a modem , sometimes called a dial-up modem. The word, modem, is derived from the combination of the words, modulate, to change into an analog signal, and demodulate, to convert an analog signal into a digital signal.

A modem usually is in the form of an adapter card that you insert in an expansion slot on a com- puter's motherboard. One end of a standard telephone cord attaches to a port on the modem card and the other end plugs into a telephone outlet.

ISDN and DSL Modems

If you access the Internet using ISDN or DSL, you need a communications device to send and receive the digital ISDN or DSL signals. An ISDN modem sends digital data and information from a computer to an ISDN line and receives digital data and information from an ISDN line. A DSL modem sends digital data and information from a computer to a DSL line and receives digital data and information from a DSL line. ISDN and DSL modems usually are external devices, in which one end connects to the telephone line and the other end connects to a port on the system unit.

Cable Modems

A cable modem is a digital modem that sends and receives digital data over the cable television (CATV) network (Figure 8-18). With more than 110 million homes wired for cable television, cable modems provide a faster Internet access alternative to dial-up for the home user and have speeds similar to DSL. Cable modems currently can transmit data at speeds that are much faster than either a dial-up modem or ISDN.

Wireless Modems

Some mobile users have a wireless modem that uses the cell phone network to connect to the Internet wirelessly from a notebook computer, a smart phone, or other mobile device (Figure 8-19). Wireless modems, which have an external or built-in antenna, are available as PC Cards, ExpressCard modules, and flash cards.

Network Cards

A network card is an adapter card, PC Card, ExpressCard module, USB network adapter, or flash card that enables a computer or device that does not have networking capability to access a network. The network card coordinates the transmission and receipt of data, instructions, and information to and from the computer or device containing the network card.

Network cards are available in a variety of styles (Figure 8-20). A network card for a desktop computer is an adapter card that has a port to which a cable connects. A network card for mobile computers and devices is in the form of a PC Card, ExpressCard module, USB network adapter, or a flash card. Network cards that provide wireless data transmission also are available. This type of card, sometimes called a wireless network card, often has an antenna.

A network card follows the guidelines of a particular network communications standard, such as Ethernet or token ring. An Ethernet card is the most common type of network card.

Wireless Access Points

A wireless access point is a central communications device that allows com- puters and devices to transfer data wirelessly among themselves or to transfer data wire- lessly to a wired network (Figure 8-7 on page 303). Wireless access points have high-quality antennas for optimal signals.

Routers

A router is a communications device that connects multiple computers or other routers together and transmits data to its correct desti- nation on the network. A router can be used on any size of network. On the largest scale, routers along the Internet backbone forward data packets to their destination using the fastest available path. For smaller business and home networks, a router allows multiple computers to share a single high-speed Internet connection such as a cable modem or DSL modem (Figure 8-21). These routers connect from 2 to 250 computers.

To prevent unauthorized users from accessing files and computers, many routers are protected by a built-in firewall, called a hardware firewall. Some also have built-in antivirus protection. Today's routers or combination wireless access point/routers are easy to configure and secure against unauthorized access.

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LESSON 6 - COMMUNICATION DEVICES - TEACHING COMPUTER NETWORKING

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A communications device is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device. One type of communications device that connects a communications channel to a sending or receiving device such as a com- puter is a modem. Computers process data as digital signals.

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*SOFTWARE
•Transmission media consist of materials or substances capable of carrying one or more signal (Shelly,2018)
•A communication channel or transmission media on which the data, instruction,or information travel

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*SOFTWARE
Wired/physical transmission media

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The core of a fiber-optic cable consists of dozens or hundreds of thin strands of glass or plastic that use light to transmit signals. Each strand, called an optical fiber, is as thin as a human hair. Inside the fiber-optic cable, an insu- lating glass cladding and a protective coating surround each optical fiber (Figure 8-26).

Fiber-optic cables have the following advantages over cables that use wire, such as twisted-pair and coaxial cables:

Capability of carrying significantly more signals than wire cables

Faster data transmission

Less susceptible to noise (interference) from other devices such as a copy machine

Better security for signals during transmission because they are less susceptible to noise

Smaller size (much thinner and lighter weight)

Disadvantages of fiber-optic cable are it costs more than twisted-pair or coaxial cable and can be difficult to install and modify. Despite these limitations, many local and long- distance telephone companies are replacing existing telephone lines with fiber-optic cables, enabling them to offer fiber Internet access to home and business users.

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LESSON 8 - PHYSICAL TRANSMISSION MEDIA - TEACHING COMPUTER NETWORKING

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The core of a fiber-optic cable consists of dozens or hundreds of thin strands of glass or plastic that use light to transmit signals. Each strand, called an optical fiber, is as thin as a human hair. Inside the fiber-optic cable, an insu- lating glass cladding and a protective coating surround each optical fiber (Figure 8-26).

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Many users opt for wireless transmission media because it is more convenient than installing cables. In addition, businesses use wireless transmission media in locations where it is impossible to install cables. Types of wireless transmission media used in communications include infrared, broadcast radio, cellular radio, microwaves, and communications satellites.

As discussed earlier in the chapter, infrared (IR) is a wireless transmission medium that sends signals using infrared light waves. Mobile computers and devices, such as a mouse, printer, and smart phone, often have an IrDA port that enables the transfer of data from one device to another using infrared light waves.

Broadcast radio is a wireless transmission medium that distributes radio signals through the air over long distances such as between cities, regions, and countries and short distances such as within an office or home. Bluetooth, UWB, Wi-Fi, and WiMAX communications technologies discussed earlier in this chapter use broadcast radio signals.

Cellular radio is a form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cell phones. A cell phone is a telephone device that uses high-frequency radio waves to transmit voice and digital data messages.

Some mobile users connect their notebook computer or other mobile computer to a cell phone to access the Web, send and receive e-mail, enter a chat room, or connect to an office or school network while away from a standard telephone line. Read Looking Ahead 8-2 for a look at the next generation of cellular communications.

Personal Communications Services ( PCS ) is the term used by the United States Federal Communications Commission (FCC) to identify all wireless digital communications. Devices that use PCS include cell phones, PDAs, pagers, and fax machines.

Microwaves are radio waves that provide a high-speed signal transmission. Microwave transmission, often called fixed wireless, involves sending signals from one microwave station to another (shown in Figure 8-1 on page 296). Microwaves can transmit data at rates up to 4,500 times faster than a dial-up modem.

A microwave station is an earth-based reflective dish that contains the antenna, transceivers, and other equipment necessary for microwave communications. Microwaves use line-of-sight transmission. To avoid possible obstructions, such as buildings or mountains, microwave stations often sit on the tops of buildings, towers, or mountains.

Microwave transmission is used in environments where installing physical transmission media is difficult or impossible and where line-of-sight transmission is available. For example, microwave transmission is used in wide-open areas such as deserts or lakes; between buildings in a close geo- graphic area; or to communicate with a satellite. Current users of microwave transmission include universities, hospitals, city governments, cable television providers, and telephone companies. Home and small business users who do not have other high-speed Internet connections available in their area also opt for lower-cost fixed wireless plans.

A communications satellite is a space station that receives microwave signals from an earth-based station, amplifies (strengthens) the signals, and broadcasts the signals back over a wide area to any number of earth-based stations.

These earth-based stations often are microwave stations. Other devices, such as smart phones and GPS receivers, also can function as earth-based stations. Transmission from an earth-based station to a satellite is an uplink. Transmission from a satellite to an earth-based station is a downlink.

Applications such as air navigation, television and radio broadcasts, weather forecasting, video conferencing, paging, global positioning systems, and Internet connections use communications satellites. With the proper satellite dish and a sat- ellite modem card, consumers access the Internet using satellite technology. With satellite Internet connections, however, uplink transmissions usually are slower than downlink transmissions. This difference in speeds usually is acceptable to most Internet satellite users because they download much more data than they upload. Although a satellite Internet connection is more expensive than cable Internet or DSL connections, sometimes it is the only high-speed Internet option in remote areas.

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LESSON 9 - WIRELESS TRANSMISSION MEDIA - TEACHING COMPUTER NETWORKING

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Many users opt for wireless transmission media because it is more convenient than installing cables. In addition, businesses use wireless transmission media in locations where it is impossible to install cables. Types of wireless transmission media used in communications include infrared, broadcast radio, cellular radio, microwaves, and communications satellites.

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1. Attack by viruses

When computers are connected by a network,the virus can spread itself electronically,at computer speeds
2. Slow service
As more users log onto the network and request files,send things to be printed and open more software applications,the network can start to slow down
3. High cost
Every workstation needs a network interface card to enable it to be connected to the network. Other hardware such as hubs, switches and routers are often needed

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•The configuration of computer devices,and media on a network

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Diagram:

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Each computer or mobile device called a  peer, have equal responsibilities and capabilities,sharing hardware,data or information with other computers and mobile devices on the peer-to-peer network

Suitable for small network. Connects fewer than 10 computers

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Diagram:

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One or more computers act as a server,and other computers on the network request services from the server

Client are other computers and mobile devices on the network that rely on the server for its resources

SERVER controls access to the hardware, software,and other resources on the network and provides a centralized storage area for programs,data,and information

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Peer-to-peer

Easy and inexpensive to set up the network

More reliable because failure of one peer will not affect other peers

All the peers can share their resources to other.

Client/server

Centralized control by the server promotes better security and managey of the network.

Data backup and recovery is easier since all data is stored in the server.

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Peer-to-peer

Lack of security control or other management function.

Data recovery or backup is very difficult. Each computer has to maintain its own backup system

Client/server

High cost to set up and maintain the network.

Less reliable because too dependent on the server;failure of server will affect the operations of the whole network.

Network congestion may occur if too many clients request services from server at the same time.

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1. Home peer-to-peer 🏡
- Accessibility of resources is limited (within home,school)
- sharing network printer

2. Internet peer-to-peer
-  scope of accessibility is world wide
-  download movie from P2P network
(eg : BitTorrent)

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• Network usually are classified as a local area network (LAN) and wide area network (WAN).

•The main difference among these classification is their area of coverage.

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A wireless LAN (WLAN) is a LAN that uses no physical wires

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A WAN can be one large network or can consist of multiple LANs connected together

• The Internet is the world's largest WAN

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Prerequisite - Types of area networks - LAN, MAN and WAN
Local Area Network (LAN):
LAN is a group of network devices which allow the communication between connected devices. The private ownership has the control over the local area network rather than public. LAN has short propagation delay than MAN as well as WAN. It covers the smallest area such as: College, School Hospital and so on.

Wide Area Network (WAN):
WAN covers the large area than LAN as well as MAN such as: Country/Continent etc. WAN is expensive and should or might not be owned by one organization. PSTN or Satellite medium are used for wide area network.

Let's see the difference between LAN and WAN:

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Difference between LAN and WAN - GeeksforGeeks

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Prerequisite - Types of area networks - LAN, MAN and WAN Local Area Network (LAN): LAN is a group of network devices which allow the communication between connected devices. The private ownership has the control over the local area network rather than public. LAN has short propagation delay than MAN as well as WAN.

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Internet is a worldwide collection of network that connect millions of businesses, government agencies, educational institution,and individuals.

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Facilitates communication

Provide abundant information

Improves education

Provide convenience through online application

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Theft of personal information

Expose to malware threats

Expose to pornography

Social disconnect

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• An intranet is a private network of an organization's information or operations with its employees.

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• Extranet is a private network of an organization that securely share parts of organisation's information with its suppliers,vendors,partners,customer or other organization.