Chapter 2 communications Flashcards
memorise all definations (54 cards)
What is a LAN
-Sharing of data between devices on a network
-Sharing of resources possible(software/hardware applications
-central management (security, backup)
-covers a small geographical area
-connections are physical(twisted cabel pair, coaxial cabels or wifi)
-privately owned infrastructure
-high data transfer rate
-easier to implement protection compared to a WAN
-low congestion
What is a WAN
-Sharing of data and resources between devices
-central management
-covers a large geographical area
-connections often virtual (PSTN, Satlink)
-often publicly owned infrastructure
-low data transfer rate
-high congestion
What are networked devices and the benifits
Networked devices are devices, interconnected on a network for high data transmission rate, it aids in resource sharing(network connected outputdevices like printers), file sharing, and storage (network connected storga emediums)
What is a Client Server Model
-its basically a dedicated server that provides applications (user, security adminstration) for client computer to use.
-webpages/data saved on servers
-client sends request to server
-server processes the request
-client displays results to user
-users computer is client
-server can host shared files
-users can request files from any client computer
-files can be accessed simultaneously by users
-egs(receiving and sending emails, using a print or file server, companies or schools centrally storing files, DBMS, domaincontroller server)
What are the features of a peer to peer network
-its basically a decentralised network where each connected computer stores data and operates independantly as peer as both a client and server
-all computers are of equal status
-each computer gives access to data/resources
-computers can communicate and share resources
-each computer resposible for its own security
-used in internet and ad hocs
What are the drawbacks of peer to peer network
-reduced security (no central management) so computers are at risk to viruses from other computers
-No central management of backup-If one computer loses its data its lost to all of them
-No central management of files, hence hard to maintain consistency
-computers have slow responce time due to being accessed by other computers.
-Files may not be available as all computers may not always be switched on
peer to peer vs client server
-client server has centralised back up, peer to peer does not.
-peer to peer has less initial set up cost compared to client server.
-in client server centralised server prevents illegal usage.
-less traffic in peer to peer(simulataneous actions)
-improved security in client server due to centralised server.
-peer to peer still operates if a device goes down, but client server wont operate if server goes down.
What is a thick client
-server performs minimal processing for client
-most resources are installed locally ,clients do most processes independantly
-works offline
-no lag due to network
-expensive
-malware threats possible due to dependence on local devices
-outlook, word, exel, playstation traditional pcs
What is a thin client
-server performs all processes required by task
-client only sends requet and displays result
-inexpensive, as no demanding hardware required
-improved security as cannot run unauthorised harmful software
-internet connections required
-may lag
-browsers, Apllle tv and strwmaing devices ,google docs, gmail
Bus Topology (peer-to-peer)
-uses a single central cabel to which all devices are connected with terminators on end to prevent signal reflection.
-Data can only travel in one direction
Advantages
-easy to expand, little cabling
-failiure of one node does not affect the network
Disadvatages
-if main cabel fails, whole network goes down
-performance of network detoirates under heavy loading
-the network not secure since each packet passes every node
-if data send between 2 devices other devices may not transmit
How data is transmitted
Each node looks a the packet and determines whather the addrss is recipeient if not it is ignored, best used for small office envoirnments
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Star Topology(client Server)
-consists of a central hub/switch and other -devices connected via dedicated connections only to server (bidirectional)
Advantages
-fewer collisions, due to high performance as each device only connected to swithc
-Easily scalable as devices connect directly to switch
-More resiliant as not reliant on a single cable
-More secure and easily upgradable
Disadvantages
-initial installation costs high
-if central switch fails entire network goes down
How Data is Transmitted
-data from sending device sent to router
-data has receiving device address
-routerdetermines recipients destination address using routing table
-router transmits data directly and only to recipient.
evolving networks
Hub sends data every device switch uses routing table
Mesh Topology (peer to peer)
-Every node is directly interconnected
-multiple routes between devices
-computers act as relays forwarding packets to final destinations
-routing is when nodes are given a routing logic so data forwarded to device in shortest route possible directly(can be rerouted)
-flooding is sending data to all nodes contributing to traffic and loading
Advantages
-If one line goes down alternate routes are available
-Improved security as not dependant on one main line
-fewer collisions as more routes avilable
-new nodes can be added without interfering with others(expandable)
-Easy to identify faults
Disadvantages
-Large cabling
-Expensive
-setup and maintanance difficult and complex
Hybrid Topology
-mix of 2 or more topologies
Advantages
-they can handel large volumes of traffic
-easy to identify where network fault has occured
-very well suited for creation of larger networks
-expandable
disvantage is very complex to install ,configure and maintain, and high cost, and difficult troubleshooting
Cloud Computing
Cloud sofwares can can perform tasks on local device with no internet
cloud provider hosts software with maintaincece etc for a monthly fee, connected using device wb browser and sneding request and connect to required software application
-method of data storage where data is stored and accessed in offsite remote servers
Advantages
-can be free
-saves storage on existing device
-data will be backed up
-data redundancy
-accesable from any device
-better securtiy
-scalable and easily shared
-offers almost unlimited storage capacity
Disadvantages
-only accesible with internet
-long time to dounload/upload data
-can be expensive in long term
-reliant on third party for security and back up
-cant access files if server goes down
Public cloud
-Services offered by a third party over the internet, avialbale to anyone with appropiate software/equipment .
Adva
-cost effective
-scalable
-accessible
disadv
-loss of control as data stored on external infrastructure
-less secure
-may not meet idustiny regulations and reccuring cost
Private cloud
-Services offered by a private internal network, only avialble to select users
-dedicated system only accessible from organisation
adv
-secure, customisable, better perfomance
disadv
-requires expertise, expensive, less scalability(hardware needed)
Hydrid Cloud
-combination or private and public clouds, some data is priv and some in public.
adv:felxible, cost efficent, bussiness continuity
diadv: complex to manage, dependent on compliance, security challanges(management)
Cloud Software
-softwares accessed via browsers such as google docs
-cloud provider hosts and manages software applications
-maintainance upgrade etc fo monthly fee
-jut contact cloud connect internet open browser itll load
-its fully tested and dont reside on user device
-if connection lost data may be stored and local device and up/doload when connection restored
Wired Networks
-High bandwith good for streaming larger files
-more reliable and stable connection and less vulnurable to interference
-more secure confidential data can be transfered securly
Wireless Networks
adv
-freedom of movement
-easily expandible
-less cabling
-allows access in remote locations
disv
-higher latency
-affected by wheather
-slower transmission speed
-direct line of sight needed
-less secure (ez to interpret radio nd microwaves)
-stopped by thick walls’
Bluetooth
-uses electromagnetic radiation as carrier of data transmission
-receives and sends radiowaves in a band of 79 freq (channels_(2.45 GHz)
-automatically detects other bluetooth devices
-no interference as each communicatingpair uses different channel
-if channel occupied uses another(spread spectrum frequency hopping) and switches channel every seconds for security
-creats secure WPAN based on key encryption
adv and useful wehn
-transferring between devices less then 30 m apart
-speed of transmission not critical
-low bandwidth apllication
Wi-fi
-uses electromagnetic radiation as carrier of data transmission
-operating full scale networks due to faster transfer rates, better range and security than bluetooth.
-a device connected to wifi can access internet wirelessly at any WAP
Waves
radio waves carries data wirelessly in the form of electromagnetic waves
bandwidth
infrared>micro>radio
penetration
radio>micro>infrared
attenuation
radio>micro>infra
infras stopped anywhere and effected amplitude so indoor use good
Satellites
-communication device on Earths orbit
-receives and transmits data
-curvature on earth hinders communication usuing electromagnetic waves so satellites used.
-communication between antennae and atellite done by micro or radiowaves
-diff frequency bands used to evade intterfferences and allow different networks to spread across earth
-microwaves easily affected by wheather and need clear line of sight
-microwaves cannot bent so need satallites to tackle curvature of earth, used in satalite communications tv mobile phone signals or wireless networks and can carry loads of data
