The Internet and the World Wide Web CHAPTER 3 The Internet and the World Wide Web

LEARNING OUTCOMES At the end of this class, students should be able to: Describe the telecommunication system Explain and differentiate the types of computer networks

CHAPTER REVIEW Basic Elements in Telecommunications System Sending and receiving devices Communication channels Connection devices Data transmission specifications Types of Networks LAN MAN WAN

Communications Today Numerous applications depend on communication systems—E-mail, Instant messaging (IM) and Social Networking. Connectivity uses computer networks to link people and resources. Wireless revolution Use of mobile or wireless devices Many devices can and will connect to one another without any physical connection Picture source: http://www.boredofstudies.org/wiki/Characteristics_of_communication_systems Connectivity is a concept related to using computer networks to link people and resources Microcomputers. minicomputers, and mainframes can all be connected Wireless revolution Use of mobile or wireless devices The revolution is the support of more than just the wireless telephone Many devices can and will connect to one another without any physical connection

THE TELECOMMUNICATION SYSTEM Electronic systems that transmit data from one location to another Communication systems can be wired or wireless Four basic elements: Sending and receiving devices Communication channel Connection devices Data transmission specifications Electronic systems that transmit data from one location to another Communication systems can be wired or wireless Basic elements Sending and receiving devices – computer or a specialized communication device Communication channel – carries the message Connection devices – act as an interface between sending and receiving devices Data transmission specifications – rules and procedures that coordinate the sending and receiving devices

Sending and Receiving Devices These are often a computer or specialized communication device. They send as well as receive messages in the form of data, information and/or instructions.

Communication Channels Channels carry data from one computer to another Two categories of communication channels Physical connection Wireless connection Channels are essential to a communication system They carry data Types of channels Telephone lines (key term) Coaxial cables Fiber-optic cable (key term) Infrared (key term) Broadcast radio (key term) Microwave (key term) Satellite

Physical Connections Twisted-pair cable (Telephone lines) consists of twisted pair cable; slowest; being phased out by more advanced and reliable media Coaxial cable single solid copper core; 80 times transmission of twisted pair; television and computer networks Fiber-optic cable 26,000 times capacity of twisted pair cable; more secure and reliable; best over limited distances; lighter, more reliable, and less expensive than coaxial cable Telephone lines – consists of twisted pair cable; slowest; being phased out by more advanced and reliable media Coaxial cable – single solid copper core; 80 times transmission of twisted pair; television and computer networks Fiber optic – 26,000 times capacity of twisted pair cable; more secure and reliable; best over limited distances; lighter, more reliable, and less expensive than coaxial cable

Wireless Connections Wireless connections do not use a solid substance to connect; uses the air itself Types of wireless connections are: Infrared Light waves used over short distances Sometimes called line of sight communications Sending and receiving devices must be in clear view of one another Examples: mouse, wireless keyboard, printer Broadcast radio Uses towers called transceivers Web-enabled devices follow a standard known as Wi-Fi (wireless fidelity) Wireless connections do not use a solid substance to connect; uses the air itself Types of wireless connections are: Infrared Light waves used over short distances Sometimes called line of sight communications Sending and receiving devices must be in clear view of one another Broadcast radio Uses towers called transceivers (key term) Web-enabled devices follow a standard known as Wi-FI (wireless fidelity) Microwave Uses high-frequency radio waves Also line of sight Used for short distances Bluetooth used for distances up to 33 feet (not line of sight) Satellite uses satellites orbiting about 22,000 miles above the earth as microwave relay stations; many of these offered by Intelsat, the International Telecommunications Satellite Consortium which is owned by 114 governments and forms a worldwide communications system Satellites can be used to send and receive data; Uplink (key term) is sending data to satellite and Downlink (key term) refers to receiving data from a Satellite GPS (Global Positioning system) (key term) use a network of 24 satellites owned and managed by the Defense Department which continuously sends location information to earth

Wireless Connections Types of wireless connections are: Satellite Microwave Uses high-frequency radio waves Also line of sight Used for short distances Bluetooth used for distances up to 33 feet (not line of sight). Satellite Satellite uses satellites orbiting about 22,000 miles above the earth as microwave relay stations Satellites can be used to send and receive data; Uplink is sending data to satellite and Downlink refers to receiving data from a Satellite GPS (Global Positioning system) use a network of 24 satellites owned and managed by the Defense Department which continuously sends location information to earth. Wireless connections do not use a solid substance to connect; uses the air itself Types of wireless connections are: Infrared Light waves used over short distances Sometimes called line of sight communications Sending and receiving devices must be in clear view of one another Broadcast radio Uses towers called transceivers (key term) Web-enabled devices follow a standard known as Wi-FI (wireless fidelity) Microwave Uses high-frequency radio waves Also line of sight Used for short distances Bluetooth used for distances up to 33 feet (not line of sight) Satellite uses satellites orbiting about 22,000 miles above the earth as microwave relay stations; many of these offered by Intelsat, the International Telecommunications Satellite Consortium which is owned by 114 governments and forms a worldwide communications system Satellites can be used to send and receive data; Uplink (key term) is sending data to satellite and Downlink (key term) refers to receiving data from a Satellite GPS (Global Positioning system) (key term) use a network of 24 satellites owned and managed by the Defense Department which continuously sends location information to earth

Communication Channels Summary

Connection Devices These devices act as an interface between the sending and receiving devices and the communication channel.

Connection Device Signals Types of modem signals Analog telephone signals; continuous electronic wave Digital computer signals; presence or absence of an electronic pulse; on/off Signals Sent analog – telephone signals; continuous electronic wave Sent digital – computer signals; presence or absence of an electronic pulse; on/off

Connection Device - Modem Modem is short for modulator-demodulator. Modulation is the process of converting from digital to analog. Demodulation is the process of converting from analog to digital. The modem enables digital microcomputers to communicate across analog telephone line.

Connection Device Types and Transfer Speeds Types of modems External stands apart from the computer is typically connected with a cable Internal built into the computer system unit already PC Card credit card-size expansion board that is inserted into portable computers; telephone cable connects the modem to the telephone wall jack Wireless may be external, internal, or a PC card Does not use cables Signals are sent through the air Transfer Speed or transfer rate is measured in bits per second; the higher the speed the faster the transfer rate Modem – modulator-demodulator External – stands apart from the computer is typically connected with a cable Internal – built into the computer system unit already PC card – credit card-size expansion board that is inserted into portable computers; telephone cable connects the modem to the telephone wall jack Wireless modem (key term) may be external, internal, or a PC card Does not use cables Signals are sent through the air Transfer Speed (key term) or transfer rate (key term)-measured in bits per second; the higher the speed the faster the transfer rate Transfer Speeds

Data Transmission Specifications It is the rules and procedures that coordinate the sending and receiving devices.

Networks A computer network is a communication system that connects two or more computers. The benefit of network is: It allows information exchange and share resources A computer network is a communication system that connects two or more computers so that they can exchange information and share resources

TYPES OF NETWORK Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN) Communications networks differ in geographical size. Three important types are: 1)LANs Computers and devices linked in close proximity to each other Linked by cable Typically use a bus (key term) form of organization With gateways, LANs can be connected to other LANs or any other type of network Home Networks – LANs are now being commonly used by individuals in home/apartments; allow different computers to share resources including a common Internet connection; can be connected by various means including a wireless LAN (key term) (WLAN) that uses radio frequencies to connect computers Home networking includes the following: Radio frequency, telephone lines, electric wiring, cables, NIC/adapter cards 2)MANs (metropolitan area network)– also known as a regional network; (key term) span distances up to 100 miles Network linking nodes and resources within the geographical bounds of a city Cellular phones can extend the reach of a MAN 3)WANs (wide area networks) Countrywide and worldwide networks Use microwave relays and satellites to reach users Internet is the widest WAN

Local Area Network (LAN) Networks with nodes that are in close physical proximity, within the same building for example, are called local area network. Typically, LANs span distances less than a mile and are owned and operated by individual organizations. LANs are widely used by colleges, universities and other types of organizations to link microcomputers and to share printers and other resources. LAN

Metropolitan Area Network (MAN) MANs span distances up to 100 miles. It is frequently used as links between office buildings that are located throughout a city. Unlike a LAN, a MAN is typically not owned by a single organization. Rather, it is either owned by a group of organization who jointly own and operate the network or by a single network service provider who provides network services for a fee.

Wide Area Network (WAN) Wide area network are countrywide and worldwide networks. Typically, WANs span distances greater than 100 miles. WANs use microwave relays and satellite to reach users over long distances, for example, from Malaysia to Japan. The widest of all WANs is the Internet, which spans the entire globe.