Presentation is loading. Please wait.

Presentation is loading. Please wait.

Lecture 5 Communications and Networks

Similar presentations

Presentation on theme: "Lecture 5 Communications and Networks"— Presentation transcript:

1 Lecture 5 Communications and Networks

2 Communications What is computer communications?
A process in which one computer transfers data, instructions, and information to another computer(s) a d c b e f

3 Uses of Communications Technologies
Voice mail Fax Chatroom Instant Message FTP Newsgroup Telephony Videoconference Groupware Global Positioning System (GPS)

4 share data and information facilitate communications
Networks share data and information What is a network? A collection of computers and devices connected by communications channels Facilitates communications among users Allows users to share resources facilitate communications share hardware share software

5 Networks What is a local area network (LAN)?
Network that connects computers and devices in a limited geographical area. Often uses Ethernet protocol

6 Networks What is a node ? Each computer or device on a network
What is a node ? Each computer or device on a network often the nodes are connected to the LAN via cables node node a wireless LAN (WLAN) is a LAN that uses no physical wires node node node

7 Networks What is a network operating system?
The system software that organizes and coordinates the activities on LAN Also called a network OS or NOS Administration Adding, deleting, and organizing users and performing maintenance tasks File management Locating and transferring files Printer management Prioritizing print jobs and reports sent to specific printers on the network Security Monitoring and, when necessary, restricting access to network resources

8 Networks What are servers and clients? Server
file server stores and manages files Server Controls access to the hardware and software on the network Provides a centralized storage are for programs Dedicated servers perform a specific task Clients Other computers on the network Rely on the server for resources print server manages printers and print jobs database server stores and provides access to a database network server manages network traffic

9 Networks What is an Internet use of peer-to-peer (P2P)?
An Internet network that enables users with the same networking software to connect to each other’s hard disks and exchange files directly Napster and Gnutella are two examples of P2P

10 Networks What is a network topology?
The configuration, or physical arrangement, of the devices in a communications network Networks usually use combinations of three topologies bus ring star

11 Networks What is a bus network?
Consists of a single central cable, to which all computers and other devices connect The bus is the physical cable The bus is also called the backbone Inexpensive and easy to install personal computer personal computer personal computer personal computer personal computer

12 Networks What is a ring network?
A cable forms a closed ring, or loop, with all computers and devices arranged along the ring Data travels from device to device around the entire ring

13 Networks What is a star network?
All of the devices connect to a central computer/hub All data that transfers from one computer to another passes through the hub personal computer personal computer personal computer host computer personal computer printer file server

14 Networks What is an intranet?
has a Web server What is an intranet? An internal network that uses Internet technologies Generally make company information accessible to employees and facilitate working in groups Typically also includes a connection to the Internet uses TCP/IP technologies accessible via a Web browser supports multimedia Web pages coded in HTML users can post and update information on the intranet by creating and posting a Web page

15 Networks What is an extranet?
Allows customers or suppliers to access part of a company’s intranet

16 Networks What is a firewall?
Hardware and/or software that restricts access to data and information on a network personal computer printer personal computer corporate network personal computer Internet firewall personal computer personal computer personal computer personal computer

17 Networks What is a home network?
Multiple computers connected together in a home or home office All computers in the house can connect to the Internet at the same time Access files and programs on the other computers in the home Share peripherals

18 Networks What is an intelligent home network?
Extends the basic home network to include features such as lighting control, thermostat adjustment, and a security system

19 Communications Software
What is communications software? Consists of programs that help you establish a connection to another computer or network Manages the transmission of data, instructions, and information

20 Costs no more than making a regular call
The Telephone Network What is a dial-up line? A temporary connection that uses one or more analog telephone lines for communications A modem at the sending end dials the telephone number of a modem at the receiving end Advantages Costs no more than making a regular call Computers at any two locations can establish a connection using modems and the telephone network Disadvantage Cannot control the quality of the connection because the telephone company’s switching office randomly selects the line

21 Can be analog or digital
The Telephone Network What is a dedicated line? A connection that always is established between two communications devices The quality and consistency of the connection is better because dedicated lines provide a consistent connection Can be analog or digital Digital lines transfer data and information at faster rates than analog lines

22 The Telephone Network What is transfer rate?
The speed with which a line carries data and information The faster the transfer rate the faster you can send and receive data and information Usually are expressed as bits per second (bps) bits per second (bps) kilobits per second (Kbps) megabits per second (Mbps) gigabits per second (Gbps)

23 The Telephone Network What are popular types of digital dedicated lines? ISDN DSL T-carrier CATV ATM

24 Communications Devices
What is a communications device? Any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device Sometimes the device must convert the data, instructions, and information from analog to digital signals or vice versa cable modems dial-up modems ISDN and DSL modems network interface cards

25 Communications Devices
What is a modem? A communications device that converts a computer's digital signals to analog signals before they are transmitted over standard telephone lines Sometimes called a dial-up modem mo + dem modulate To change into an analog signal demodulate To convert an analog signal into a digital signal

26 Communications Devices
What is a digital modem? One that sends and receives data and information to and from a digital telephone line such as ISDN or DSL ISDN modem Also called an ISDN adapter Sends and receives digital data to an ISDN line DSL modem Sends and receives digital data to a DSL line

27 Communications Devices
What is a cable modem? A modem that sends and receives data over the cable television (CATV) network Currently much faster than a dial-up modem or ISDN Usually attaches to a USB port or a port on a network interface card

28 Communications Devices
What is a network interface card (NIC)? A card you insert into an expansion slot of a personal computer or other device, enabling the device to connect to a network NIC for desktop computer NIC for notebook computer

29 Communications Channel
What is a BUS? The communications path between two devices

30 Physical Transmission Media
What is twisted-pair cable? Consists of one or more twisted pair wires bundled together Each twisted pair wire consists of two separate insulated copper wires Twisted together to reduce noise Noise is an electrical disturbance that can degrade communications twisted pair cable twisted pair cable twisted pair wire

31 Physical Transmission Media
What is coaxial cable? Consists of a single copper wire surrounded by at least three layers Often called coax Often used for cable television wiring plastic outer coating woven or braided wire insulating material copper wire coaxial cable

32 Physical Transmission Media
What is fiber-optic cable? Contains a core of dozens or hundreds of thin strands of glass or plastic Uses light to transmit signals Each strand is called an optical fiber Thin as a human hair protective coating glass cladding optical fiber core cable contains many optical fibers outer covering jacket fiber-optic cable between floors of a building

33 Wireless Transmission Media
What is broadcast radio? 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 Slower and more susceptible to noise than physical transmission media transmitter sends the broadcast radio signal receiver accepts the broadcast radio signal must have an antenna that is located in the range of the signal transceiver both sends and receives signals from wireless devices

34 Wireless Transmission Media
What is cellular radio? A form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cellular telephones A cellular telephone is a telephone device that uses radio signals to transmit voice and digital data messages mobile telephone switching office (MTSO) calling party in auto cell public switched telephone network cell cell base station (microwave station) cell called party

35 Wireless Transmission Media
What is a microwave station? An earth-based reflective dish that contains the equipment necessary for microwave communications Microwaves are extremely high-speed signals Line-of-sight towers Must transmit in a straight line

36 Wireless Transmission Media
What is a communications satellite? A space station that receives microwave signals from an earth-based station, amplifies the signals, and broadcasts the signals back over a wide area to any number of earth-based stations Transmission to a satellite is an uplink Transmission from a satellite to an earth-based station is a downlink

37 Wireless Transmission Media
What is infrared (IR)? A wireless transmission media that sends signals using infrared light waves Requires a line-of-sight transmission Many computers and devices have an IrDA port that enables the transfer of data using infrared light rays

Download ppt "Lecture 5 Communications and Networks"

Similar presentations

Ads by Google