Introduction to Computing Slides By ADEELA MUSTAFA Communications
Introduction to Computing Slides By ADEELA MUSTAFA
Communications and Networks (9 th –Chapter) Communications a process in which two or more computers or devices transfer data, instructions, and information. Today, even the smallest computers and devices can communicate directly with one another, around the globe — often via the Internet. Some communications involve cables and wires; others are sent wirelessly through the air. For successful communications-: • A sending device that initiates an instruction to transmit data, instructions, or information. • A communications device that connects the sending device to a communications channel. • A communications channel, or transmission media on which the data, instructions, or information travel.
Communications and Networks • A communications device that connects the communications channel to a receiving device. • A receiving device that accepts the transmission of data, instructions, or information. All types of computers and mobile devices serve as sending and receiving devices in a communications system. This includes mainframe computers, servers, desktop computers, notebook computers, smart phones, portable media players, handheld game consoles, and GPS receivers.
Communications and Networks
Communications and Networks Uses of Computer Communications Wireless Messaging Services Users can send and receive wireless messages to and from smart phones, cell phones, handheld game consoles, and other mobile devices and computers using three techniques: text messaging, picture/video messaging, and wireless instant messaging The type of messaging you use depends primarily on the services offered by the wireless Internet service provider (WISP) that works with the cell phone or other mobile device you select. In most cases, you can receive these messages at no cost but pay a per use or monthly fee to send messages to others.
d n a ns io t a c ks i n u r o m w Com Net Users can send and receive text messages, picture/video messages, and wireless instant messages to and from their smart phones and other computers and devices.
Communications and Networks Text Messaging A mobile device with text messaging, also called SMS (short message service), capability allows users to send and receive short text messages, Text messaging services typically provide users with several options for sending and receiving messages: • Mobile to Mobile: send a message from your mobile device to another mobile device. • Mobile to E-Mail: send a message from your mobile device to an e-mail address anywhere in the world. • Web to Mobile: send a message from a text messaging Web site to a mobile device, or request that a Web site alert a mobile device with messages of breaking news and other updates, such as sports scores, stock prices, and weather forecasts. • Mobile to Provider: send a message by entering a common short code (CSC), which is a four- or five-digit number assigned to a specific content or wireless service provider, followed by the message, such as a vote for a television program contestant.
Communications and Networks Wireless Instant Messaging Wireless instant messaging (IM) is a real-time Internet communications service that allows wireless mobile devices to exchange messages with one or more mobile devices or online users. Some WISPs partner with IM services so that you can use your smart phone or other mobile device to send and receive wireless instant messages. AT&T’s wireless service, for example, allows communications through various instant messengers such as AIM (AOL Instant Messenger), Windows Live Messenger, and Yahoo! Messenger. With a compatible IM service, users have these IM options: (1) Mobile to Mobile (2) Mobile to Personal Computer (3) Web to Mobile
Communications and Networks
Communications and Networks
Communications and Networks Wireless Internet Access Points Users access wireless Internet access points with computers or devices that have the necessary built-in wireless capability or the appropriate wireless network card, USB network adapter, Express -Card module, or PC Card. Two types of wireless Internet access points are hot spots and mobile wireless networks. A hot spot is a wireless network that provides Internet connections to mobile computers and devices. Through the hot spot, mobile users check e-mail, browse the Web, and access any service on the Internet. Two hot spot technologies are Wi-Fi and Wi. MAX.
Communications and Networks Global Positioning Systems A global positioning system (GPS) is a navigation system that consists of one or more earth-based receivers that accept and analyze signals sent by satellites in order to determine the receiver’s geographic location. A GPS receiver is a handheld, mountable, or embedded device that contains an antenna, a radio receiver, and a processor. Many include a screen display that shows an individual’s location on a map. Many mobile devices such as smart phones have GPS capability built into the device or as an add-on feature. Some users carry a handheld GPS receiver; others mount a receiver to an object such as an automobile, boat, airplane, farm and construction equipment, or computer. Many vehicles use GPSs to provide drivers with directions or other information, such as alternate traffic routes, automatically call for help if the airbag is deployed, dispatch roadside assistance, unlock the driver’s side door if keys are locked in the car, and track the vehicle if it is stolen.
Communications and Networks Voice Mail Voice mail, which functions much like an answering machine, allows someone to leave a voice message for one or more people. Unlike answering machines, however, a computer in the voice mail system converts an analog voice message into digital form. Once digitized, the message is stored in a voice mailbox. A voice mailbox is a storage location on a hard disk in the voice mail system. To help users manage voice mail messages, some systems offer visual voice mail. With visual voice mail, users can view message details such as the length of calls and, in some cases, read message contents instead of listening to them. Some voice mail systems can send audio voice mail files to e-mail addresses. Others can convert a voice mail message to a text message for display on a computer or mobile device such as a smart phone, which you then can manage like any other text message.
Communications and Networks A network is a collection of computers and devices connected together via communications devices and transmission media. Many businesses network their computers together to (1)facilitate communications, (2)share hardware, (3)share data (4)share software. LANs, MANs, and WANs Networks usually are classified as a local area network, metropolitan area network, or wide area network. The main differentiation among these classifications is their area of coverage.
Communications and Networks LAN A local area network (LAN) LAN is a network that connects computers and devices in a limited geographical area such as a home, school computer laboratory, office building , or closely positioned group of buildings. Each computer or device on the network, called a node, often shares resources such as printers, large hard disks, and programs. Often, the nodes are connected via cables.
Communications and Networks Computers on different floors access the same local area network (LAN) in an office building.
Communications and Networks MAN A metropolitan area network (MAN) is a high-speed network that connects local area networks in a metropolitan area such as a city or town and handles the bulk of communications activity across that region. A MAN typically includes one or more LANs, but covers a smaller geographic area than a WAN. A MAN usually is managed by a consortium of users or by a single network provider that sells the service to the users. Local and state governments, for example, regulate some MANs. Telephone companies, cable television operators, and other organizations provide users with connections to the MAN.
Communications and Networks WAN A wide area network (WAN) is a network that covers a large geographic area (such as a city, country, or the world) using a communications channel that combines many types of media such as telephone lines, cables, and radio waves. A WAN can be one large network or can consist of two or more LANs connected together. The Internet is the world’s largest WAN.
Communications and Networks Star Network On a star network, all of the computers and devices (nodes) on the network connect to a central device, thus forming a star. Two types of devices that provide a common central connection point for nodes on the network are a hub and a switch. All data that transfers from one node to another passes through the hub or switch. Star networks are fairly easy to install and maintain. Nodes can be added to and removed from the network with little or no disruption to the network. On a star network, if one node fails, only that node is affected. The other nodes continue to operate normally. If the hub or switch fails, however, the entire network is inoperable until the device is repaired. Most large star networks, therefore, keep backup hubs or switches available in case the primary one fails.
Communications and Networks A star network contains a single, centralized hub or switch through which all the devices in the network communicate.
Communications and Networks Bus Network A bus network consists of a single central cable, to which all computers and other devices connect. The bus is the physical cable that connects the computers and other devices. The bus in a bus network transmits data, instructions, and information in both directions. When a sending device transmits data, the address of the receiving device is included with the transmission so that the data is routed to the appropriate receiving device. The greatest risk to a bus network is that the bus itself might become inoperable. If that happens, the network remains inoperative until the bus is back in working order.
Communications and Networks Devices in a bus network share a single data path.
Communications and Networks Ring Network On a ring network, a cable forms a closed loop (ring) with all computers and devices arranged along the ring. Data transmitted on a ring network travels from device to device around the entire ring, in one direction. When a computer or device sends data, the data travels to each computer on the ring until it reaches its destination. If a computer or device on a ring network fails, the entire network potentially could stop functioning. A ring network can span a larger distance than a bus network, but it is more difficult to install. The ring topology primarily is used for LANs, but also is used in WANs.
Operating Systems & Utility Programs On a ring network, all connected devices form a continuous loop.
Communications and Networks Network Communications Standards Today’s networks connect terminals, devices, and computers from many different manufacturers across many types of networks, such as wide area, local area, and wireless. For the different devices on various types of networks to be able to communicate, the network must use similar techniques of moving data through the network from one application to another. For example, an IBM mainframe computer cannot communicate directly with an Apple Macintosh network some form of translation must occur for devices on these two types of networks to communicate. To alleviate the problems of incompatibility and ensure that hardware and software components can be integrated into any network, various organizations such as ANSI and IEEE (pronounced I triple E) propose, develop, and approve network standards.
Communications and Networks A network standard defines guidelines that specify the way computers access the medium to which they are attached, the type(s) of medium used, the speeds used on different types of networks, and the type(s) of physical cable and/or the wireless technology used. A standard that outlines characteristics of how two network devices communicate is called a protocol. Specifically, a protocol may define data format, coding schemes, error handling, and sequencing techniques. Hardware and software manufacturers design their products to meet the guidelines specified in a particular standard, so that their devices can communicate with the network.
Communications and Networks Ethernet is based on a bus topology, but Ethernet networks can be wired in a star pattern. The Ethernet standard defines guidelines for the physical configuration of a network, cabling, network cards, and nodes. Today, Ethernet is the most popular network standard for LANs because it is relatively inexpensive and easy to install and maintain. Ethernet networks often use cables to transmit data. At a 10 Mbps (million bits per second) data transfer rate, the original Ethernet standard is not very fast by today’s standards. A more recent Ethernet standard, called Fast Ethernet, has a data transfer rate of 100 Mbps, ten times faster than the original standard. Gigabit Ethernet provides an even higher speed of transmission, with transfer rates of 1 Gbps (1 billion bits per second). The 10 -Gigabit Ethernet standard supports transfer rates up to 10 Gbps, 40 -Gigabit Ethernet up to 40 Gbps, and 100 -Gigabit Ethernet up to 100 Gbps.
Communications and Networks Token Ring The token ring standard specifies that computers and devices on the network share or pass a special signal, called a token, in a unidirectional manner and in a preset order. A token is a special series of bits that function like a ticket. The device with the token can transmit data over the network. Only one token exists per network. This ensures that only one computer transmits data at a time. Token ring is based on a ring topology (although it can use a star topology). The token ring standard defines guidelines for the physical configuration of a network, cabling, network cards, and devices. Some token ring networks connect up to 72 devices. Others use a special type of wiring that allows up to 260 connections. The data transfer rate on a token ring network can be 4 Mbps, 16 Mbps, 100 Mbps, or 1 Gbps.
Communications and Networks TCP/IP Short for Transmission Control Protocol/ Internet Protocol, TCP/IP is a network standard, specifically a protocol, that defines how messages (data) are routed from one end of a network to the other, ensuring the data arrives correctly. TCP/IP describes rules for dividing messages into small pieces, called packets; providing addresses for each packet; checking for and detecting errors; sequencing packets; and regulating the flow of messages along the network. When a computer sends data over the Internet, the data is divided into packets. Each packet contains the data, as well as the recipient (destination), the origin (sender), and the sequence information used to reassemble the data at the destination. Each packet travels along the fastest individual available path to the recipient’s computer via communications devices called routers. This technique of breaking a message into individual packets, sending the packets along the best route available, and then reassembling the data is called packet switching.
Network communications use a variety of standards to ensure that data travels correctly to its destination. Some standards used in Internet communications include the TCP/IP and Ethernet standards,
Communications and Networks Wi-Fi Computers and devices that have the appropriate wireless capability can communicate via radio waves with other computers or devices using Wi-Fi (wireless fidelity), which identifies any network based on the 802. 11 standards. Developed by IEEE, 802. 11 is a series of network standards that specifies how two wireless devices communicate over the air with each other. A designation of 802. 11 a/b/g on a computer or device indicates it supports those three standards (a, b, and g). The newest standard, 802. 11 n, uses multiple transmitters and receivers, known as MIMO (multiple-input multiple-output), to reach speeds from 2 to 10 times faster than 802. 11 g.
Communications and Networks
Communications and Networks Wi-MAX Wi. MAX (Worldwide Interoperability for Microwave Access), also known as 802. 16, is a network standard developed by IEEE that specifies how wireless devices communicate over the air in a wide area. Using the Wi. MAX standard, computers or devices with the appropriate Wi. MAX wireless capability communicate via radio waves with other computers or devices via a Wi. MAX tower. The Wi. MAX tower, which can cover up to a 30 -mile radius, connects to the Internet or to another Wi. MAX tower. Two types of Wi. MAX specifications are fixed wireless and mobile wireless. With fixed wireless Wi. MAX, a customer accesses the Internet from a desktop computer at home or other permanent location, Fixed wireless Wi. MAX has data transfer rates up to 40 Mbps, while mobile wireless Wi. MAX has data transfer rates up to 15 Mbps.
How Wi. MAX Works
Communications and Networks WAP The Wireless Application Protocol (WAP) is a standard, specifically a protocol, that specifies how some mobile devices such as smart phones can display the content of Internet services such as the Web, e-mail, and chat rooms. To display a Web page on a smart phone, the phone should contain a microbrowser. WAP works in conjunction with the TCP/IP network standard. WAP uses a client/ server network. The wireless device contains the client software, which connects to the Internet access provider’s server.
Communications and Networks Communications Software Communications software consists of programs that (1) help users establish a connection to another computer or network, (2) manage the transmission of data, instructions, and information, (3) provide an interface for users to communicate with one another. The first two are system software and the third is application software. examples of application software for communications: e-mail, FTP, Web browser, chat rooms, instant messaging, video conferencing, and Vo. IP.
Communications and Networks Communications over the Telephone Network The public switched telephone network (PSTN) is the worldwide telephone system that handles voice-oriented telephone calls. Nearly the entire telephone network today uses digital technology, with the exception of the final link from the local telephone company to a home, which often is analog. The telephone network is an integral part of computer communications. Data, instructions, and information are transmitted over the telephone network using dial-up lines or dedicated lines.
A ne sam tw ple or k c tele on ph fig on ur e at ion
Communications and Networks Dial-Up Lines A dial-up line is a temporary connection that uses one or more analog telephone lines for communications. A dial-up connection is not permanent. Using a dial-up line to connect computers costs no more than making a regular telephone call. Dedicated Lines A dedicated line is a type of always-on connection that is established between two communications devices (unlike a dial-up line where the connection is reestablished each time it is used). The quality and consistency of the connection on a dedicated line are better than a dial-up line because dedicated lines provide a constant connection.
Communications and Networks Five types of digital dedicated lines are ISDN lines, DSL, FTTP, T-carrier lines, and ATM. Although cable television (CATV) lines and fixed wireless are not a type of telephone line, they are very popular ways for the home user to connect to the Internet. Fixed wireless Internet connections use an antenna on your house or business to communicate with a tower location via radio signals.
Communications and Networks ISDN Lines For the small business and home user, an ISDN line provides faster transfer rates than dial-up telephone lines. Not as widely used today as in the past, ISDN (Integrated Services Digital Network) is a set of standards for digital transmission of data over standard copper telephone lines. With ISDN, the same telephone line that could carry only one computer signal now can carry three or more signals at once through the same line, using a technique called multiplexing.
Communications and Networks DSL is a popular digital line alternative for the small business or home user. DSL (Digital Subscriber Line) transmits at fast speeds on existing standard copper telephone wiring. Some DSL installations include a dial tone, providing users with both voice and data communications. These DSL installations often require that filters be installed to reduce noise interference when voice communications share the same line. ADSL is one of the more popular types of DSLs. As shown in, ADSL (asymmetric digital subscriber line) is a type of DSL that supports faster transfer rates when receiving data (the downstream rate) than when sending data (the upstream rate). ADSL is ideal for Internet access because most users download more information from the Internet than they upload.
ADSL connections transmit data downstream (receiving) at a much faster rate than upstream (sending)
Communications and Networks Communications Devices A communications device is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device. At the sending end, a communications device sends the data, instructions, or information from the sending device to a communications channel. At the receiving end, a communications device receives the signals from the communications channel. Dial-Up Modems A dial-up modem is a communications device that can convert digital signals to analog signals and analog signals to digital signals, so that data can travel along an analog telephone line. Recall that an analog signal consists of a continuous electrical wave, and a digital signal consists of individual electrical pulses that represent bits grouped together into bytes. For example, a dial-up modem connected to a sending computer converts the computer’s digital signals into analog signals. The analog signals then can travel over a standard telephone line. At the receiving end, if necessary, another dialup modem converts the analog signals back into digital signals that a receiving computer can process.
A cable modem. A typical cable m odem installatio n
Communications and Networks 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. Wireless modems, which have an external or built-in antenna, are available as USB flash drives, Express Card modules, PC Cards, and memory cards. Some smart phones also can function as a wireless modem when connected with a special cable to a personal computer.
Communications and Networks Routers A router is a communications device that connects multiple computers or other routers together and transmits data to its correct destination on a 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 through a cable modem or DSL modem. 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.
Communications and Networks Through a router, home and small business networks can share access to a high-speed Internet connection such as through a cable or DSL modem.
Communications and Networks Hubs and Switches Today, thousands of computer networks exist, ranging from small networks operated by home users to global networks operated by numerous telecommunications firms. Inter connecting these many types of networks requires various types of communications devices. A hub or switch is a device that provides a central point for cables in a network. Larger networks typically use a hub, while smaller networks use a switch. Some hubs and/or switches include routers. That is, the hub or switch receives data from many directions and then forwards it to one or more destinations.
Communications and Networks A hub or switch is a central point that connects several devices in a network together.
Communications and Networks Home Networks Many home users are connecting multiple computers and devices together in a home network. Home networking saves the home user money and provides many conveniences. Each networked computer in the house has the following capabilities: • Connect to the Internet at the same time • Share a single high-speed Internet connection • Access files and programs on the other computers in the house • Share peripherals such as a printer, scanner, external hard disk, or optical disc drive • Play multiplayer games with players on other computers in the house • Connect game consoles to the Internet • Subscribe to and use Vo. IP
Communications and Networks Wired Home Networks (1)Ethernet Network (2) Phone-line Network Power-line Cable Network A home power line cable network is a network that uses the same lines that bring electricity into the house. This network requires no additional wiring. One end of a cable plugs in the computer’s USB port and the other end of the cable plugs in a wall outlet. The data transmits through the existing power lines in the house.
Communications and Networks Communications Channel A communications channel is the transmission media on which data, instructions, or information travel in a communications system. The amount of data, instructions, and information that can travel over a communications channel sometimes is called the bandwidth. The higher the bandwidth, the more the channel transmits. For example, a cable modem has more bandwidth than a dial-up modem. Latency is the time it takes a signal to travel from one location to another on a network. A communications channel consists of one or more transmission media. Transmission media consist of materials or substances capable of carrying one or more signals. Broadband media transmit multiple signals simultaneously. In many cases, download transfer rates of broadband are faster than its upload transfer rates. Home and business users today opt for broadband Internet access because of the fast transfer rates. Figure 9 -34 This figure shows an example of sending a request over the Internet using a communications channel.
Physical Transmission Media Physical transmission media used in communications include twisted-pair cable, coaxial cable, and fiber-optic cable. These cables typically are used within or underground between buildings. Ethernet and token ring LANs often use physical transmission media. The speeds of various physical communications media when they are used in LANs. Communications and Networks
Communications and Networks Twisted-Pair Cable One of the more widely used transmission media for network cabling and telephone systems is twisted-pair cable. Twisted-pair cable consists of one or more twisted -pair wires bundled together. Each twisted-pair wire consists of two separate insulated copper wires that are twisted together. The wires are twisted together to reduce noise. Noise is an electrical disturbance that can degrade communications.
Communications and Networks Coaxial Cable Coaxial cable, often referred to as coax (pronounced KO-ax), consists of a single copper wire surrounded by at least three layers: (1) an insulating material, (2) a woven or braided metal, and (3) a plastic outer coating. Cable television (CATV) network wiring often uses coaxial cable because it can be cabled over longer distances than twisted-pair cable. Most of today’s computer networks, however, do not use coaxial cable because other transmission media such as fiber-optic cable transmit signals at faster rates.
Communications and Networks Fiber-Optic Cable 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 insulating glass cladding and a protective coating surround each optical fiber. Advantages over cables that use wire: • 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.
Communications and Networks A fiber-optic cable consists of hair-thin strands of glass or plastic that carry data as pulses of light.
Communications and Networks The transfer rates of various wireless transmission media. Wireless Transmission Media It is more convenient than installing cables. In addition to convenience, businesses use wireless transmission media in locations where it is impossible to install cables.
Communications and Networks Infrared 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 Ir. DA port that enables the transfer of data from one device to another using infrared light waves. Broadcast Radio 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. Examples Bluetooth, Wi-Fi, and Wi. MAX communications technologies
Communications and Networks Cellular Radio Cellular radio is a form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cell phones. only a limited number of radio frequencies exist • 1 G (first generation) transmitted analog data • 2 G (second generation) transmit digital data at speeds from 9. 6 Kbps to 19. 2 Kbps • 3 G (third generation) transmit digital data at speeds from 144 Kbps to 2. 4 Mbps • 4 G (fourth generation) transmit digital data at speeds up to 15 Mbps The most recent cellular network category, the 4 G network, uses the mobile wireless Wi. MAX communication standard. Several major communications companies have worked together to develop a nationwide 4 G network.
Communications and Networks 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 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. As with infrared, 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.
Communications and Networks Communications Satellite 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 earthbased Stations These earth-based stations often are micro wave stations. Other devices, such as smart phones and GPS receivers, also can function as earthbased 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. Communications satellites are placed about 22, 300 miles above the Earth’s equator.
End Thank You All (have a nice day)
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