Computing Wireless networking

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Internet
A collection of inter-connected networks(the world wide web is just a smaller segment of this)
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WAN
Wide Area NetwokComputers connected over a large geographical area using resources supplied by a third party carrier,
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IP address
Internet protocol An address thats distinguishes one network form another(every network has one)A laptops ip can change if you travel to a different network with it
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circuit switching network
a dedicated connection is set up between you and the person you are calling for the duration of the call and it requires packet switching
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packet switching
Where a file is broken down into smaller segments to send as there are not enough lines for everyone
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Packets contents
The IP (Internet Protocol) address it is going to The IP address it has come from The sequence number of the packet The number of packets in the whole communication Error checking data
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how are packets sent
routers direct packets across other nodes/routers to get to the receiver the quickest using the least busy route
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(DNS)
Domain Name System DNS technology allows you to type a name such as google.co.uk into your web browser by translating what you type into an ip address. The data is stored in DNS servers
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NIC
Network Interface Cards Built into every networked device Wired or wireless allows a connection to your router
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MAC addressing
A Media Access Control (MAC) address is assigned to each Network Interface Card (NIC) by the manufacturer. It looks like this: 3B:14:E6:39:0A:2C. Every networked device in the world has a unique one.When you request a web page, each router along the
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LAN
Local Area Network Small geographical network
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networking(advantages)
Resources such as printers are shared saving money, You can access your files from any computer in the network, Data is easy to back up as it is stored centrally on the server
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networking(disadvantages)
The networking hardware is expensive, Managing a large network is complicated, Viruses may be able to infiltrate the network and infect every computer
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Star topology
all terminals are connected to one central Hub/switch which is connected to a server
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Star topology(advantages)
Not many collisions so faster data transfer and if one of the cables or terminal fail the rest of the network will still function
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Star topology(disadvantages)
Additional hardware such as the switch is required and if the central device fails everything else does as well
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Mesh topology
All terminals in the network are connected together and there is no central server. they relay data to each other
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partial mesh network
some terminals in the connected to each other(there is not a link form each one to every other terminal)Also no central server Often used in conjunction with star topology s to create larger networks
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Wireless mesh networks
have potential to cover entire organisations as only one node needs a wired connection the rest just connect to each other wirelessly
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mesh network(Advantages)
No single point of failure, Expansion can be done without disrupting the entire network, data can be simultaneously transmitted by different devices
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mesh network(disadvantages)
expensive to install cables if using them, can involve redundant connections, network maintenance and administration is difficult
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Network hardware needed for LAN
to connect a LAN you will need a NIC in each computer as well as a router to provide access to a local area network
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router
Sends data packets on their way in the best direction which has the least traffic so gets there the quickest
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Hub
When a packet is received it broadcasts the packets to all devices on the network. IT is a central multi-plug adaptor for computers and printers in a network
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Switch
Smart multi-plug adaptor only sends packets to the intended recipient, using its MAC address so there is less network traffic
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Ethernet protocols
It is how devices format data ready to send(when nodes need to send information they will wait for the connection to be "quiet" before transmitting.Two nodes attempting to transmit simultaneously will stop and wait random periods before reattempting
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Virtual networks
Segments of a larger physical network are configured to behave as though they are part of a separate, and much smaller network, which is encrypted
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WAP
Wireless access point Allows wireless devices to connect to a wired network
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2.4GHz channel
Greater range and coverage, More interference from other devices, and only three non-overlapping channels
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5GHz channel
Less crowded space with 23 non-overlapping channels with higher data transmission rates, Fewer devices can use the 5GHz frequency, less able to penetrate through walls
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encryption
Encryption is the encoding of data so that it can no longer be easily understood
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Plaintext
the original message to be encrypted
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Ciphertext
the encrypted message
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Encryption:
the process of converting plaintext into ciphertext
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Key:
a sequence of numbers used to encrypt or decrypt, often data using a mathematical formula
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Encryption algorithm:
the formula for encrypting the plaintext
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Private key (Symmetric encryption)
A single key is used to encrypt and decrypt a message and must be given to the recipient of your message to decrypt the data
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Public key (Asymmetric encryption)
Two keys are used - one to encrypt and the other to decrypt data This is more secure as it means that you never have to send or reveal your decryption key
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Cryptanalysis
The objective of cryptanalysis is to decode the ciphertext – typically by finding out the secret key
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The server
The server is a powerful computer which provides services or resources required by any of the clients. It waits for requests and then finds the data to resend to the client
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A client
A client is a computer which requests the services or resources provided by the server The client sends requests to the server Waits for a reply Receives the reply
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Client-server networking
where a central server is used to perform processing tasks and carries out requests form the clients on the network, Can support hundreds or even thousands of users and grow with an organisation
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Client-server networking(advantages)
data is backed up centrally, all data i held in one place so security is better and users can log on from any computer in the network and access their data
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Peer-to-peer (P2P) structure
A peer-to-peer network has no central server and is useful for small companies with few computers where files can be accessed from all computers in the network usefully for small businesses and schools
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Peer-to-peer (P2P) structure(advantages)
easy to set up as computers can be cabled together, no special software required,computers share hardware such as printers and routers, users can directly share each others files
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Peer-to-peer (P2P) structure(disadvantages)
viruses can easily spread through the network, each computer needs to backup its own data, files may be hard to locate as they are not stored centrally so may be badly ordered
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Peer-to-peer on a WAN
used for BBC iplayer and can be easily used for illegal distribution of copyright material such as films and music
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Hosting
An Internet host is a company (often an ISP) that is able to store your files and make them available to you or others from other Internet-connected computers
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The Cloud
The ‘Cloud’ is a term used to refer to resources, data and information hosted on remote servers
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Advantages of Cloud Computing
Backing up data is no longer crucial – it is done by the service provider You can access your data and applications from anywhere at any time There is also no need for a powerful computer
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Disadvantages of Cloud Computing
The idea of handing over important data to another company worries some people, Sensitive data could be more vulnerable to hacking, While you can usually store a limited amount of data for free, you have to pay to store more than the free allowance
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transmission media(Copper cable)
advantages: tried and trusted technology,relatively inexpensive disadvantages:signal affected by electric and magnetic fields,low bandwidth,very heavy cables
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transmission media(fibre optics)
advantages:very fast transmission,low loss of signal over distance,require very little power disadvantages:high investment cost,need for expensive optical transmitters and receivers
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transmission media(Wireless transmission)
advantages:no need for trailing wires (safer),allows devices to be used anywhere provided there is a signal,easier to add devices to a network disadvantages:data transmission rate less than wired systems,signal can be blocked by objects or walls
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Factors affecting network performance
Bandwidth, Latency, Error rate/collisions, Retransmission rate
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Bandwidth
The amount of data that can be carried at a time
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Connection Speeds
Measured in Mbps (Megabits per Second)
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Latency
Latency is determined by the speed of delivery, or time delay between the moment the first data packet of a communication starts and when it is received at its destination
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Errors, collisions and retransmission
Errors and high network traffic may result in data collisions between packets When packets collide, they are corrupted or lost Lost packets are retransmitted, and this process takes longer owing to the bandwidth and latency of the network
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HTTP
(hypertext transfer protocol) is used for accessing and receiving web pages in the form of HTML files on the Internet, The protocol requests the web server to upload the requested web page to the user’s browser for viewing
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HTTPS
(secure protocol) encrypts the information so that it cannot be understood if it is hacked
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FTP
(File Transfer Protocol) Used for sending or retrieving files to or from a remote server or computer
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POP and IMAP
Post office protocol and internet message access protocol POP will download entire messages to your local device and delete them from the server but IMAP will just copy it from the server without deleting it
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SMTP
(Simple Mail Transfer Protocol) Email protocol used for transferring email between remote email servers
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TCP/IP
(Transmission Control Protocol) breaks the information into packets and sends them when it receives it reassembles them(internet protocol) routes the individual packets
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The TCP/IP protocol stack
The protocol stack defines four layers in which different protocols operate to pass data packets across a network(Andy Travels Near London)
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Application layer
selects the correct protocol to use depending on what you are doing(banking would be https for security)
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Transport layer
Here the connection is made between to the two computers and agree on communication settings and the size of the packets
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Network layer
Destination addresses are written on to the packets ready for transmission
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Data link layer
is the physical hardware connecting the two hosts(cabling and nics)
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Receiving packets
data packets move back up the layers in the opposite way these layers are good as they are self contained
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Other cards in this set

Card 2

Front

Wide Area NetwokComputers connected over a large geographical area using resources supplied by a third party carrier,

Back

WAN

Card 3

Front

Internet protocol An address thats distinguishes one network form another(every network has one)A laptops ip can change if you travel to a different network with it

Back

Preview of the back of card 3

Card 4

Front

a dedicated connection is set up between you and the person you are calling for the duration of the call and it requires packet switching

Back

Preview of the back of card 4

Card 5

Front

Where a file is broken down into smaller segments to send as there are not enough lines for everyone

Back

Preview of the back of card 5
View more cards

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