Communications

transcript

Communications

Slides By Rana Usman SattarStudent Of BBA(Hons)PMAS Arid Agriculture University RawalpindiGmail: ranaa.usman@gmail.comFacebook: usman.shan86@yahoo.com

Communications

• Computer communications describes aprocess in which two or more computers ordevices transfer data, instructions, and information.

Components of Communication

• A sending device that initiates an instruction to transmit data, instructions, or information. (Sender)

• A communications device that connects the sending device to a communications channel. (Encoder)

• A communications channel, or transmission media on which the data, instructions, or information travel. (Medium)

• A communications device that connects the communications channel to a receiving device. (Decoder)

• A receiving device that accepts the transmission of data, instructions, or information. (Reciever)

Networks

• a network is a collection of computers and devices connected together via communications devices and transmission media.• A network can be internal to an organizationor span the world by connecting to the Internet.

Advantages of Network:

Facilitating communications

• Using a network, people communicate Efficiently and easily via e-mail, instant messaging, chat rooms, blogs, wikis, online social networks, video telephone calls, online meetings, videoconferencing, VoIP, wireless messaging services, and groupware.

Sharing hardware

• In a networked environment, each computer on the network can have access to hardware on the network.• Business and home users network theirhardware to save money.

Sharing software

• Users connected to a network have access to software on the network.• To support multiple users’ access of software, most vendors sell network versions or site licenses of their software, which usually cost less than buying individual copies of the software for each computer.

Transferring funds

• Called electronic funds transfer (EFT ), it allows users connected to a network to transfer money from one bank account to another via transmission media.• Consumers use an ATM to access theirbank account. Businesses deposit payrollchecks directly in employees’ bank accounts.

LANs, MANs, and WANs

• A local area network (LAN) is anetwork that connects computers and devicesin a limited geographical area such as a home,school computer laboratory, office buildingor closely positioned group ofbuildings.

Wireless LAN

• A wireless LAN (WLAN) is a LAN thatuses no physical wires. Computers and devicesthat access a wireless LAN must have built-inwireless capability or the appropriate wirelessnetwork card, USB network adapter,ExpressCard module, PC Card, or flash card.

A metropolitan area network (MAN) isa high-speed network that connects local areanetworks in a metropolitan area such as a cityor town and handles the bulk of communications activity across that region.

• A wide area network (WAN) is anetwork that covers a large geographic area(such as a city, country, or the world) using acommunications channel that combines manytypes of media such as telephone lines, cables,and radio waves

Network Architectures

• The design of computers, devices, andmedia in a network, sometimes calledthe network architecture, is categorized aseither client/server or peer-to-peer.

Client/Server

• On a client/server network,one or more computers act as a server, andthe other computers on the network requestser vices from the server• A server, sometimes called a host computer, controls access to the hardware, software, andother resources on the network and providesa centralized storage area for programs, data,and information.

Client/Server

• The clients are other computersand mobile devices on the networkthat rely on the server for its resources.

For example, a server might store a database ofcustomers. Clients on the network (companyemployees) access the customer database onthe server.

Peer-to-Peer

• One type of peer-to-peer networkis a simple, inexpensive network that typicallyconnects fewer than 10 computers.• Each computer, called a peer, has equal responsibilities and capabilities• Each computer stores files on its ownstorage devices. Thus, each computer on thenetwork contains both the server operatingsystem and application software.

Internet Peer-to-Peer

• Internet network on which users access each other’s hard disks and exchange files directly over the Internet.• This type of peer-to peer network sometimes is called a file sharing network because users with compatible software and an Internet connection copy files from someone else’s hard disk to their hard disks. (BitTorrent , Kazaa)

Internet

Network Topologies

• A network topology refers to the layout ofthe computers and devices in a communicationsnetwork.• Three commonly used network topologiesare star, bus, and ring.

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.• Star networks are fairly easy to install andmaintain. Nodes can be added to and removedfrom the network with little or no disruption tothe network.

Bus Network

• A bus network consists of a single central cable, to which all computers and other devices connect.• 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.

Bus Network

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.

Intranets

• An intranet (intra means within) is an internal network that uses Internet technologies.• Intranets generally make company information accessible to employees and facilitate working in groups.

Intranets

Simple intranet applications include:• Electronic publishing• telephone directories• event calendars• procedure manuals• employee benefits• job postings

Extranets

• Sometimes a company uses an extranet,which allows customers or suppliers to accesspart of its intranet.• Package shipping companies, for example, allow customers to accesstheir intranet to print air bills, schedule pickups,and even track shipped packages as thepackages travel to their destinations.

Network CommunicationsStandards

• 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.

protocol

• A standard that outlines characteristicsof how two network devices communicateis called a protocol. Specifically, a protocolmay define data format, coding schemes, error

handling, and sequencing techniques.

TCP/IP

• TCP/IP is a network standard,specifically a protocol, that defines howmessages (data) are routed from one end of anetwork to the other, ensuring the data arrivescorrectly. • TCP/IP describes rules for dividingmessages into small pieces, called packets;providing addresses for each packet; checkingfor and detecting errors; sequencing packets;and regulating the flow of messages along thenetwork.

Ethernet

• Ethernet is a network standard that specifies nocentral computer or device on the network (nodes)should control when data can be transmitted;that is, each node attempts to transmit data whenit determines the network is available to receivecommunications. • If two computers on an Ethernetnetwork attempt to send data at the same time,a collision will occur, and the computers mustattempt to send their messages again.

Token Ring

• The token ring standard specifies thatcomputers and devices on the network shareor pass a special signal, called a token, in aunidirectional manner and in a preset order.• A token is a special series of bits that function likea ticket. The device with the token can transmitdata over the network. Only one token exists pernetwork. This ensures that only one computertransmits data at a time.

Example of How Communications Standards Work Together

• Wi-Fi (wireless fidelity), which identifiesany 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.

Bluetooth

• Bluetooth is a network standard, specificallya protocol, that defines how two Bluetoothdevices use short-range radio waves to transmit data. The

data transfers between devices at a rate of up to 3 Mbps.

• A Bluetooth device contains a small chip thatallows it to communicate with other Bluetoothdevices. Examples of Bluetooth-enabled devicescan include desktop computers, notebook computers,handheld computers, smart phones.

• UWB, which stands for ultra-wideband, is anetwork standard that specifies how two UWBdevices use short-range radio waves to

communicate at high speeds with each other.• At distances of 10 meters (about 33 feet), the

data transfer rate is 110 Mbps. At closer distances, such as 2 meters (about 6.5 feet), the transfer rate is at least 480 Mbps.

• IrDA standard is used to transmit data wirelessly to each other via infrared (IR) light waves.

• The devices transfer data at rates from 115 Kbps (thousand bits per second) to 4 Mbps between their IrDA ports.

• RFID (radio frequency identification) is a standard, specifically a protocol, that defines

how a network uses radio signals to communicate with a tag placed in or attached to an object, an animal, or a person. The tag, called a transponder, consists of an antenna and a memory chip that contains the information to be transmitted via radio waves.

• WiMAX (Worldwide Interoperability forMicrowave Access), also known as 802.16, isa network standard developed by IEEE thatspecifies how wireless devices communicateover the air in a wide area. Using the WiMAXstandard, computers or devices with the

appropriate WiMAX wireless capability communicate via radio waves with other computers or devices via a WiMAX tower.

TYPES OF WIMAX

• Fixed wireless With fixed wirelessWiMAX, a customer accesses the Internetfrom a desktop computer at home or otherpermanent location.• Mobile wireless Mobile wireless WiMAX,by contrast, enables users to access the WiMAXnetwork with mobile computers and mobiledevices such as smart phones.

• 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.

A WAP-enabled smartphone.

Communications Software

• Communications software consists ofprograms 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.

Communications over theTelephone Network

• The public switched telephone network (PSTN) is the worldwide telephone system that handles voice-oriented telephone calls.

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. Usinga 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-onconnection 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.

Five types of digital dedicated lines

• ISDN lines• DSL• FTTP• T-carrier lines• ATM

Communications Devices

• A communications device is any type ofhardware capable of transmitting data,

instructions, and information between a sending device and a receiving device.

Dial-Up Modems

• A dial-up modem is a communications devicethat can convert digital signals to analog signals

and analog signals to digital signals, so that data can travel along an analog telephone line.

Digital Modems

• A digital modem is a communications devicethat sends and receives data and information to

and from a digital line.• ISDN Modem• DSL Modem• CABLE Modem

Wireless Modems

• 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.

Wireless Modems

Network Cards

• A network card, sometimes called a networkinterface card (NIC pronounced nick), is a

communications device that enables a computer or device that does not have built-in networking capability to access a network.

Network Cards

Routers

• A router is a communications device thatconnects multiple computers or other routerstogether and transmits data to its correct

destination on a network. • A router can be used on any size of network.

Routers

Hubs and Switches

• 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.

Hubs and Switches

Communications Channel

• Communication channel is a way to connect or communicate to a network through physical or wireless media.

Types of communication channels

• Physical transmission media• Wireless transmission media

Physical transmission media

• Physical transmission media use wires to communicate or connect to network.

• Twisted-Pair Cable• Coaxial Cable• Fiber-Optic Cable

Twisted-Pair Cable

• Twisted-pair cable consistsof one or more twisted-pair wires

bundledtogether . 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.

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• (3) a plastic outer coating

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 .

Wireless Transmission Media

• A type of media in which wireless media is use to connect or communicate to a network.

• Infrared• Broadcast Radio• Cellular Radio• Microwaves• Communications Satellite

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 IrDA port that enables the transfer of data from one device to another using infrared light waves.

Broadcast Radio

• Broadcast radio is a wireless transmissionmedium that distributes radio signals throughthe air over long distances such as between

cities, regions, and countries and short distances such as within an office or home.

Cellular Radio

• Cellular radio is a form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cell phones.

Microwaves• Microwaves are radio waves

that providea high-speed signal transmission.

Microwavetransmission, 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.

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 earth-based

Stations.

Communications

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