Computer Science Chapter 4.9 - Fundamentals of communication and networking

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69 Terms

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Serial Data Transmission

Single bits are sent one after another along a single wire.

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Parallel Data Transmission

Multiple bits are sent down several wires simultaneously.

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What happens when data skew occurs?

bits sent together may not be received together

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Bandwidth

the range of signal frequencies that may be transmitted.

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Baud rate

The rate at which signals on a wire may change.

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Bit rate

The number of bits transmitted per second.

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Latency

Time delay between the moment something is initiated and the moment the effect begins

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Crosstalk

unwanted transfer of signals between communication channels

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Synchronous data transmission

a clock signal is used to time when signals are sent.

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Asynchronous data transmission

sender and receiver have separate clocks which are not kept synchronised - a start bit is used to signal the arrival of data and to synchronise the transmitter and receiver temporarily

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Advantages of a network (5)

  • Sharing resources such as printers makes it cheaper

  • site licenses are likely to be cheaper than several standalone

  • files can be shared easily

  • work can be easily accessed using any computer on the network

  • data is easy to backup as all the data is stored on the server

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Disadvantages of a network (4)

  • Purchasing the network cabling and file servers can be expensive

  • Managing a large network is complicated - requires training and usually a network manager

  • if the file server breaks down the files on the file server become inaccessible

  • viruses can spread to other computers throughout a computer screen

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Advantages of wired networks (4)

  • reliable

  • faster (than wireless)

  • more secure

  • can extend further easier

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Disadvantages of wired networks (3)

  • can be expensive

  • less flexible (cannot easily move devices)

  • trip hazards

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Advantages of wireless networks (3)

  • cheaper

  • very flexible

  • no trip hazards

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Disadvantages of wireless networks

  • not always reliable

  • slower

  • less secure

  • don’t extend very far

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Where are Ethernet cables usually used for

You will usually find them in buildings - they connect the school computers together and are widely used in businesses

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Where/What are fibre optic and copper cables used (for)

usually used to join together houses, businesses and other locations externally

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What do copper cables use to work

electrical signals travelling along the wire (sometimes slow)

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What do fibre optic cables use to work

Fibre optic cables use light to transmit data, and light moves at the speed of light! So these cables are a lot faster (than copper cables)

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What does PAN, LAN and WAN stand for?

  • Personal area network

  • Local area network

  • Wide area network

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LAN

when computers or devices are connected together over a single geographical area, such as within a home, a building or one site. (eg. the school/home)

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WAN

when computers or devices are connected together over multiple geographical areas. (eg. the internet)

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PAN

network on a very small scale. (eg. Bluetooth)

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What are the 4 components that allow you to access the internet

The modem, the router, the switch, the WAP (Wireless access point)

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What does the modem do?

Connects the device to the internet through a phone line

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What does the router do?

A router is a networking device that forwards data packets between computer networks

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What does the switch do?

Allows you to connect multiple devices to the router

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What does the WAP do?

Lets your wireless devices connect to the network

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Whats the purpose of a stop bit?

ensures that the receiver has time to process each byte before receiving the next one

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Whats the purpose of a start bit?

temporarily synchronises the clocks in both the receiver and the transmitter

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Advantages of a bus topology

  • Cheap as it uses the least amount of cable

  • Adding another computer is easily done

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Disadvantages of a bus topology

  • Slow with many computers (has to check with every computer)

  • If the backbone breaks the whole system breaks

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Advantages of a ring topology

  • Cheap to expand

  • Does not rely on a central hub

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Disadvantages of a ring topolgy

  • slow if a lot of computers are on the system

  • If one computer breaks the whole network breaks

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Advantages of a star topology

  • If a cable fails it only affects one computer

  • Computers can be easily added

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Disadvantages of a star topology

  • more cabling needed

  • fail if the centre hub fails 

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Topology definition

The structure of the connections that connect devices to the network.

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Physical topology definition

The physical layout of the cabling between the devices on the network

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Logical topology definition

How the data flows around a network

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How does a logical bus topology work

The network will physically be set up in one way however it will logically operate like a bus topology. Using a bus protocol meaning it will check with each computer if the packet is meant for it like a bus topology

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Client server definition

A system in which some computers (the clients), request services provided by other computers, the servers

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Peer-to-peer network definition

A network that has no dedicated servers. All computers are of equal status and can both share resources themselves and use resources from other computers

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Server definition

A computer that provides shared resources to network users

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3 examples of servers

  • fie server

  • mail server

  • database server

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3 examples where peer-to-peer networks are used

  • file sharing

  • online gaming

  • streaming media

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3 examples where client servers are used

  • the internet

  • in businesses (file servers, database etc)

  • cloud services

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What is Wi-Fi

A family of related protocols that define how devices should communicate over wireless connections (WLAN)

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What does Wi-Fi allow you to do

Allows you to create a WLAN thats based on internation standards

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What two (extra) components required for wireless networking (compared to wired)

  • wireless network adaptor

  • wireless access point

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Whats a wireless network adaptor

a piece of hardware, such as a device or a card installed inside a computer, that allows a device to connect to a wireless network (like a Wi-Fi network) or the internet without using an Ethernet cable

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What are the 3 ways to make wireless networks more secure

  • Disabling SSID broadcast - means that in order to connect to the network you must already know the name of the network (SSID)

  • MAC address whitelist - You can filter out unwanted devices

  • Encryption (WPA,WPA2)

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 What is the SSID

The service set identifier - a unique ID that consists of up to 32 characters and is used for naming wireless networks

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Whats the MAC address

Media access control - Used to uniquely identify pieces of hardware

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Whats the advantages of a client-server network over a peer-to-peer network?

  • The server computer can manage security

  • Files can be stored on the server - accessed at all times even when computers are off

  • processing some tasks can be performed on servers instead of having to purchase more powerful computers

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What does CSMA/CA stand for?

Carrier sense multiple access 

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How does CSMA/CA work?

It allows a computer to listen out for transmissions - and if it hears one it waits. Then it checks again after some time and if it doesn’t hear anything it’ll wait a random short amount of time before sending the data over

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What does RTS stand for?

Ready to send

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What does CTS stand for?

Clear to send

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What does RTS and CTS do?

RTS - when the computer sends an RTS signal it is telling the WAP it is ‘ready to send’ data 

Then the WAP temporarily stops all over transmissions 

CTS - The WAP sends a CTS signal to the computer telling it that the network is clear then the computer sends over the data 

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