UNIVERSITI TENAGA NASIONAL “Generates Professionals” CHAPTER 7 : Part 1 INTRODUCTION TO NETWORKING

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Objectives Understand the history of data communications Describe the basic components of a network Explain the methods of data transmission, including types of signals, modulation, and choices among transmission modes Differentiate among the various kinds of communications links and appreciate the need for protocols

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Data Communications Systems Computer systems that transmit data over communications lines such as telephone lines or cables History –Centralized data processing in early days –Distributed data processing began in late 1960s –Networks of personal computers began in 1980s

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Centralized Data Processing Places all hardware, software, and processing in one location Very inconvenient and inefficient –Input data had to be physically transported to computer –Processed material had to be delivered to users

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Distributed Data Processing Uses computers that are at a distance from central computer Local computers had access to central computers –Some processing done on local computers, some on central computers

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Network A group of two or more computer system that are linked together to exchange data and share resources over communication lines Uses communications equipment to connect two or more computers and resources –Distributed data processing systems are networks –Local area network (LAN) designed to share data and resources among several users in office or building

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Putting Together a Network Basic Components –Sending device –Communications link –Receiving device modems routers switches (NIC) Network Interface Cards computers

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Node –Any workstation or peripheral that is connected to network  server, computer, peripheral devices, such as printer Network Interface Card(NIC) –expansion boards that fit into a computer’s expansion slot. –Provide electronic connection between a computer and the network. Network Fundamentals

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Routers –Can determine the best path to route data –If traffic is clogged on one path, the router will determine an alternative path Switches –Perform same function as router –However, it is simpler and faster mechanism than a router Network Fundamentals

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Digital and Analog Transmission Digital transmission Analog transmission Modem

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Digital Transmission Sends data as distinct pulses, either on or off –Similar to how data travels through computer

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Analog Transmission Continuous electrical signal in the form of a wave –Called carrier wave Many communications media already in place for analog (voice) transmission –Phone lines are most common Digital signal from computer must be converted to analog form to be transmitted over analog lines

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Converting Digital to Analog Carrier wave can be altered –Amplitude (height) of wave –Frequency (number of times a wave repeats during a cycle) of wave Conversion from digital to analog called modulation Conversion from analog to digital called demodulation

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Converting Digital to Analog analog signal Continuous electrical wave digital signal Distinct pulses that represent bits grouped together into bytes

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Modem Short for modulator/demodulator Converts digital signal to analog and vice versa –Modulate  convert from digital to analog –Demodulate  convert from analog to digital –Speeds up to 56,000 bps (56K) Internal modem - resides on an expansion board that plugs into a computer ADSL modem PC Card modem

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Types of Modems External modem separate from computer Internal modem inserted into computer –Standard on most computers today PC Card modem slides into slot on laptop –Roughly credit card size Cable connects modem to standard phone jack

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Modem Data Speeds Measured in bits per second (bps) –Early modems transmitted at 300 bps –Fastest current modems transmit at 56,000 bps Federal Communications Commission (FCC) restrictions prohibit actual speeds faster than 53,000 bps Actual speed depends on line conditions and other variables

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Other Communications Devices ISDN DSL Cable modems Cellular modems

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Integrated Systems Digital Network (ISDN) Special type of telephone circuit –Can move data at 128,000 bps –Includes two phone lines, so you can talk on the phone while online Drawbacks –Expensive, especially at installation –Not available in all areas TM package

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Digital Subscriber Line (DSL) Advantages of DSL: Can leave your Internet connection open and still use the phone line for voice calls. The speed is much higher than a regular modem DSL doesn't necessarily require new wiring; it can use the phone line you already have. The company that offers DSL will usually provide the modem as part of the installation.

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Digital Subscriber Line (DSL) Drawbacks A DSL connection works better when you are closer to the provider's central office. The connection is faster for receiving data than it is for sending data over the Internet. The service is not available everywhere.

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Cable Modems Uses coaxial cable already in place for your TV –Very fast transmission speed, especially for downloading –Always on: no need to dial a connection Drawbacks –All users share a cable segment’s capacity As more users in neighborhood go online, speed decreases –No security for individual users or data Purchase a firewall program for security

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Cellular Modems Transmit data over the cellular telephone system –Roughly half the speed of a regular telephone network

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Data Transmission Simplex  sends data in one direction only –Example: television broadcasting Half-duplex  sends data in both directions, but only one way at a time –Example: bank teller sends data about a deposit; after data received, a confirmation returns Full-duplex  allows transmission in both directions at same time –Example: a conversation –Typically used for high-speed data communication

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Communications Media Physical means of data transmission Bandwidth is measure of the capacity of the communications link –Speed at which a line carries data and information –The faster the transfer rate, the faster you can send and receive data and information –Usually expressed as a measure of bits per second bits per second (bps) kilobits per second (Kbps) megabits per second (Mbps) gigabits per second (Gbps)

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Types of Communications Media Wire pairs Coaxial cables Fiber optics Microwave transmission Satellite transmission Wireless transmission

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Wire Pairs Also known as twisted pair –Two wires twisted around each other to reduce electrical interference Inexpensive Already in place (for telephone systems) Susceptible to electrical interference and noise –Noise - anything that causes signal distortion

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Coaxial Cable A center conductor wire surrounded by layer of insulation and metallic sheath Commonly used to connect to cable TV Higher bandwidth and less susceptibility to noise than twisted pair

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Fiber Optics Use light instead of electricity to send data Much higher bandwidth than coaxial cable Immune to electrical interference Materials cheaper than coaxial, but installation costs high

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Microwave Transmission Uses line-of-sight transmission of data signals –Sending microwave must “see” receiver Requires relay stations approximately every 30 miles –Waves are straight, earth is curved Offers high speed and cost- effectiveness Susceptible to weather conditions

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Satellite Transmission A form of microwave transmission –Satellite acts as relay station Components –Earth station sends and receives signal to satellite –Transponder receives and amplifies signal, changes frequency, and retransmits data Useful when signal must travel thousands of miles

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Wireless Transmission Transmits data over relatively short distances without wires Examples –IrDA - uses infrared line-of- sight –Bluetooth - uses radio waves to connect mobile devices – standards - govern wireless transmission

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Setting Standards Protocol - a set of rules for the exchange of data between a terminal and a computer or two computers –Agreement on how data is to be sent and receipt acknowledged –Needed to allow computers from different vendors to communicate –Transmission Control Protocol/Internet Protocol (TCP/IP) permits any computer to communicate with the Internet

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Setting Standards Three of the most common TCP/IP protocols used are: 1)HTTP (HyperText Transfer Protocol) - Used between a web client and a web server, for non-secure data transmissions. A web client (i.e. Internet browser on a computer) sends a request to a web server to view a web page. The web server receives that request and sends the web page information back to the web client. 2)HTTPS (HyperText Transfer Protocol Secure) - Used between a web client and a web server, for secure data transmissions. Often used for sending credit card transaction data or other private data from a web client (i.e. Internet browser on a computer) to a web server. 3)FTP (File Transfer Protocol) - Used between two or more computers. One computer sends data to or receives data from another computer directly.

UNIVERSITI TENAGA NASIONAL “Generates Professionals” Setting Standards The TCP/IP address for a website or web server, is typically not easy to remember. To make it easier to remember, a domain name is used instead. For example, is the IP address for the Computer Hope website and computerhope.com is the domain name. It is much easier to remember.