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DATA COMMUNICATION AND NETWORKING

INTRODUCTION

? Communications has extended our uses for the microcomputer.
? Communication systems are the electronic systems that transmit data over communications lines from one location to another.
? You can set up a network in your home or apartment using existing telephone lines.
? Competent end users need to understand the concept of connectivity, the impact of the wireless revolution, and the elements of a communications system.
? They must also understand the basics of communications channels, connection devices, data transmission, networks, network architectures, and network types.

COMMUNICATIONS

? Computer communications is the process of sharing data, programs, and information between two or more computers.

CONNECTIVITY

? Connec
tivity is a concept related to using computer networks to link people and resources
? You can use telephone lines to link to nearly any computer in the world.

THE WIRELESS REVOLUTION

? The single most dramatic change in connectivity and communications in the past five years has been the widespread use of mobile or wireless telephones.
? In 2002, it was estimated that there are over 600 million mobile telephones in use worldwide, and by 2004, almost 1.5 billion (source: Newsweek, June 7, 2004 pg 51 Next Frontiers: Your Next Computer).
? This wireless technology allows individuals to stay connected with one another from almost anywhere at any time.
? Originally developed for voice, the wireless revolution can transmit nearly any kind of information

COMMUNICATIONS SYSTEMS

▪▪▪▪▪▪▪▪▪▪▪ ?Communications systems have four basic elements

SENDING AND RECEIVING DEVICES

? Often a computer or specialized communications device.

COMMUNICATION CHANNEL (AKA TRANSMISSION MEDIUM)

? The actual connection that carries the message
? Can be a physical wire, or a wireless connection

CONNECTION DEVICE (AKA COMMUNICATIONS DEVICE)

? Act as an interface between the sending and receiving devices. They convert outgoing messages into a digital format, and back again at the receiving (incoming) end.

DATA TRANSMISSION SPECIFICATIONS

? The rules and procedures that coordinate the sending and receiving devices by precisely defining how the message will be sent across the communication channel.

PHYSICAL CONNECTIONS

TELEPHONE LINES

? Typically use twisted pair cables, copper wires covered with an insulating jacket
? Relatively inexpensive way to connect devices
? Now being phased out by more technically advanced and reliable media

COAXIAL CABLE
EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

? A high frequency transmission cable, can be used to replace multiple lines of twisted pair cable with one single, solid copper core.
? Can carry 80 times the capacity of one twisted pair cable

EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING
Fig:Un shield Twisted- Pair (UTP)
EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING
Fig:Shielded Twisted -Pair (STP)

FIBER-OPTIC CABLE
EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

? Transmit data as a pulse of light through tiny tubes of glass
? Has over 26,000 times the capacity as one twisted pair cable
? Fiber optic cables are rapidly replacing twisted pair telephone wires

WIRELESS CONNECTIONS

INFRARED

? Use infrared light waves to communicate
? Known as a “line of sight” communication medium
? Commonly used to transmit data from a PDA to a desktop PC

BROADCAST RADIO

EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

Fig: Show Radio Broadcasting

♑? Uses special sending and receiving towers called “transceivers”
? The transceiver sends and receives many signals from different wireless devices
? Cellular telephones communicate using this technology
? WiFi (Wireless Fidelity aka 802.11 technologies) are used to build wireless local area networks

MICROWAVE

? Uses high frequency radio waves
? Line of sight medium
? Transmit data over relatively short distances (within 10-20 miles) due to curvature of the earth
? Microwave signals are sometimes repeated at microwave stations with microwave dishes
? Bluetooth is a short-range wireless communication standard that uses microwaves to transmit data over very short distances (less than 33 feet). This may become popular for connecting peripheral devices to computers

SATELLITE

EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING


? Uses satellites orbiting up to 22,000 miles above the earth to send large volumes of data
? Up link is sending data to a satellite
? Down link is receiving data from a satellite
? GPS (Global Positioning Systems) use satellite data to pinpoint locations nearly anywhere on the earth. They are used for both military and commercial navigation systems

CONNECTION DEVICES

? A great deal of communication takes place over telephone lines
? Since telephone was used for voice, the technology typically used analog signals to transmit calls
? Computer use digital signals
? To connect computers via telephone lines, a system was needed to transmit data from digital to analog to digital again. Modems were created to do this.

MODEMS

? Modem is an acronym meaning “modulator – demodulator”
? Modulation converts a digital signal to an analog signal
? Demodulation converts an analog signal back to digital
? Speed at which modems communicate is measured in bits per second (bps).
? Typically modem speeds are 33.6 and 56 kbps (kilo bits per second)

EXTERNAL MODEM

? Modem circuitry housed in a separate case
? Connected to computer using a serial port, and to telephone using a phone wire and an RJ-11 jack

INTERNAL MODEM

? Modem circuitry is housed inside the computer
? Connects to telephone wall jack using a phone wire

PC CARD MODEM

? Serves as an “external modem” for a laptop
? Credit card sized expansion board to connect a laptop computer to a telephone line

WIRELESS MODEM

? Can be an external, internal, or PC Card modem, but rather than connecting to the telephone system using a wire, it connects via wireless technology (e.g. a cellular phone connection)

TYPES OF CONNECTIONS

? Standard telephone lines and modems are called dial up services
? Large organizations use higher speed connections such as T1, T2, T3, and T4 lines.
? These support all digital communications, so they don’t use modems but do require special equipment.
? They tend to be expensive, but can transmit data at high speeds, e.g. 1.5 Mbps (1,500 kbps) almost 26 times faster than standard dial up service

DIGITAL SUBSCRIBER LINE (DSL)

? A high speed Internet service offered by phone companies

CABLE MODEMS

? A high speed Internet service offered by Cable TV companies

SATELLITE/AIR CONNECTION SERVICES

? Another competitor for high speed Internet services, often offered in areas where Cable or DSL is not available

DATA TRANSMISSION PG

? Several factors affect how data is transmitted across a communication medium, including:

BANDWIDTH

VOICE BAND (AKA VOICE GRADE OR LOW BANDWIDTH)

? Standard telephone connections
? Typical speed is 56 kbps
? Low cost, but lower speed

MEDIUM BAND

? Bandwidth used in special leased lines to connect minicomputers and main frames as well as transmitting data over long distances
? Typically used by businesses and not individuals

BROADBAND

? Used for high-capacity transmissions
? Microcomputers with DSL, cable, or satellite connections use this
? Speeds are typically 1.5 Mbps, but can go higher

PROTOCOLS

? Protocols are the rules for exchanging data across a network
? A standard for the Internet is the TCP/IP protocol – Transmission Control Protocol / Internet Protocol
? Essential features of TCP/IP is for identifying the sending and receiving devices, and reformatting the data so it can be sent via the Internet

IDENTIFICATION

? Every computer on the Internet has an IP address (Internet Protocol address). This is a numeric address such as 198.45.19.151
? A Domain Name Server (DNS) converts a text based address, e.g. http://www.McGraw-Hill.com into the IP address 198.45.19.151

REFORMATTING



NETWORKS

TERMS USED

NODE

CLIENT

SERVER

HUB / SWITCH

NETWORK INTERFACE CARD (NIC)

NETWORK OPERATING SYSTEM (NOS)

DISTRIBUTED PROCESSING

HOST COMPUTER

NETWORK MANAGER

EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

ADVANTAGES

DISADVANTAGES

EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

MESH TOPOLOGIES

EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

ADVANTAGES

DISADVANTAGES

RING TOPOLOGIES

EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

ADVANTAGES

DISADVANTAGES


EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

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2 Comments

  • EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

    Vincent mories kpewa, March 1, 2024 @ 7:25 pm Reply

    Good work

  • EcoleBooks | COMPUTER A LEVEL(FORM SIX) NOTES - DATA COMMUNICATION AND NETWORKING

    OROMA Douglas, April 2, 2023 @ 10:46 am Reply

    Great

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