1.3.1 Flashcards
ISP
internet service provider is a company that provides you with access to the internet
URL
uniform resource locator is the web address of a website, it is a unique address
IP address
every hardware device connected to the internet has its own unique address, this address enables every device in the network to be identified
DNS
domain name server is the internet equivalent of a phone book
hosting
website has to be hosted n a web browser
steps for accessing a web page
- website is hosted in a webserver which as a unique IP address
2.URL is typed into the browser - browser send request to DNS server, DNS holds the website name and its corresponding IP address, the DNS gets the corresponding IP address
- if DNS cannot find the IP address, it passes a request to the higher DNS and if still not found it sends an error message
- the IP address is sent back to the browser, the browser uses the IP address to locate the server hosting website and sends a request to the webserver
- the server sends a copy of the webpage as packets which is then displayed on the browser
explain how the URL www.ocr.org.uk is converted into the IP address (3 marks)
The browser sends a request to the DNS server which holds its corresponding IP address and gets it. If DNS can not find the IP address it displays an error message. The IP address is sent back to the browser. URL sends it to DNS.
Network Interface Card
-every device on a network needs one
-each NIC has its own MAC (media access control) address
what does a MAC address do?
enables every device on a network to be uniquely identified which allows the data to be sent to the right device
Hub
-small box which links nodes together to form a network
-transmits data from one node to another, in the form of data packets
-when a data packet arrives at the hub, it is transmitted to every other node on the network
when a data packet arrives at the hub, it is transmitted to every other node on the network- why is this not efficient?
can cause data collisions
switch
-for larger networks or networks where security is important, a switch is a better option that a hub
-switch sends data packets only to intended node, switch reads the destination address from the data packet and sends it only to destination node
benefits of a switch
-security is improved
-lower risk of data collisions
router
-device which transfers data from one network to another
-without a router you would not be able to connect to the internet
-router needs data packets IP address
-router uses database routes to look up where IP address is
-identifies all of the different routes that could be used to reach the destination and sends the data packets down the fastest route
network cables
-used to join individual forms of LAN
-wired networks have a higher bandwidth than wireless
-cables used in LAN are ethernet cables, CAT-5 or CAT-6
-fibre optic cables are used to connect WANs together, they provide a high bandwidth and are able to cover a much larger distance
WAP and WiFi
-wireless access point (WAP) used to connect WiFi devices to a wired network without the need for cables
-WAPs commonly found in homes
-WAPs are similar to hubs, they do not need the MAC address of the destination packet- bandwidth is less
Hub in comparison to a switch
hub:-connects nodes on the network together, it is not intelligent
-data packets are transmitted to every node on the network
-higher risk of data collisions leading to slower network performance
-security risks because data is sent to all nodes
-less expensive than a switch
switch:-an intelligent device which connects nodes on the network together
-data packets are transmitted only to the node for which it is intended
-less risk of data collisions leading to improved network performance
-better security as data only sent to correct node
-more expensive than a hub
MAC address compared with IP address
MAC address:-cannot be changed, every device has a fixed address
-6 bytes long
-normally written in hex
-configured by hardware
-only used within the LAN (switch)
IP address:-can be changed (IPv4, IPv6)
-4 bytes long
-normally written in denary
-configured by software
-used for routing across a WAN / internet
topology
the way in which all parts of a network are arranged and connected together
-shows how data flows regardless of physical design
-includes the nodes (computers) and connecting lines (cables)
star topology
-server / central computer / switch is in the middles and cables run from the central device to each work station
advantages of star topology
-most common network layout
-fast connections
-faults are easier to trace
-relatively secure connections
-if the cable fails the other work stations keep working
-easy to add new workstations
disadvantages of star topology
-difficult to install
-expensive set up
-complex operating system
-server can get congested
-needs managing
-depends on the functioning of the central component
-if cable fails there is no other way of sending data from that workstation
mesh topology
-each node relays the data it receives to other nodes within reach
-there is no central node
-multiple paths between nodes
advantages of mesh topology
-data can be transmitted from different devices simultaneously
-highly robust
-can handle high volumes of data traffic
-adding or removing more devices will not hamper the transmission of data
-excellent for wireless networks
disadvantages of mesh topology
-expensive compared to other topologies
-self maintenance complex
-difficult to expand the network
-number of connections increases as more nodes are added
-impractical due to number of cables needed
uses of topologies
-military (allows soldiers to communicate)
-mobile hotspots (buses as wifi hotspots)
client server network
large networks have multiple servers that perform specific tasks
what servers make up a client server?
-file server
-application server
-web server
-print server
-mail server
file server
holds and maintains user files
application server
allows programs to be run over a network
web server
holds and shares webpages
print server
manages printing across a network
mail server
handles emails between users
advantages of a client server network
-easy to maintain files
-backups made centrally
-software updates can be done from central server
-clients can have personal area to store files
-shared resources, printer
-network security easy to control centrally
disadvantages of client server network
-requires specialists to maintain and set up
-maintenance expensive
-server may be overloaded with too many simultaneous requests
-if server fails all clients lose access to network
peer to peer network
-commonly found in homes and small businesses
-can access their own files and resources shared by other peers
advantages of peer to peer network
-easy maintenance
-no server dependance
disadvantages of peer to peer network
-backups have to be made directly from each individual work station
-no central file server and all nodes are equal
-nodes slow down while processing requests from other devices
-files only able to be accessed if the device that stores them is online
cloud computing
generally refers to using servers connected to the internet to run applications or store data, usually those systems are not owned or run by the people or business using them
advantages of the cloud
-data can be easily accessed from anywhere with an internet connection
-the business running the cloud computing system manages backups and security
-additional storage can be added easily, without having to invest in additional hardware
disadvantages of the cloud
-anything connect via the internet has the potential to be hacked into even though internet providers may provide additional security, data breaches can still happen
-when users have access to multiple cloud systems it can be easier for hackers to access one system from another
-control over data is given away to someone else when data is stored outside of users environment
examples of cloud storage
-dropbox: cloud storage service that enables users to store files on remote cloud servers and the ability to share files within a synchronised format
-G suite: a suite of collaborative productivity apps that offers your business professional email, shared calendars, online documents ect
why do we use networks?
-to live in a connected world
-worldwide communication
what is a network?
set of connected computers in order to share resources
stand alone computer
not part of a network, can only access data files that are directly liked to the computer
what are some advantages of networks?
-allows groups of users to share and exchange information
-brings people together
-documents can be exchanged and edited
-high security
what are some disadvantages of networks?
-need technical expertise
-could be susceptible to unauthorised access
-needs passwords to be changed regularly
describe a LAN
-confined to a small area
-usually located in a single building
-fairly cheap to build
describe WAN
-covers wide area
-lots of different buildings
-expensive to build
what are some advantages of a LAN?
-users can log into any workstation
-backups can be made centrally
-peripherals such as printers can be shared
what are some disadvantages of a LAN?
-if there’s a problem with the central server no one will be able to access files
-needs specialist support
what are some advantages of a WAN?
-data can be shared between LANs
-allows workers to collaborate even if they are geographically apart
what are some disadvantages of a WAN?
-very expensive as organisation has to hire bandwidth from telecom operators
what factors affect the performance of a network?
-speed of network
-number of users
-transmission media
-error rate
-latency
-bandwidth
what is the speed of a network measured in?
bits per second
how does the number of users affect a network performance?
bandwidth has to be shared between users
contention ratio
measures the ratio of users compared to the available bandwidth
how does the transmission media affect a network performance?
the type of cable effects the network performance
what are the different types of transmission media?
-fibre optic cables
-twisted par
-coaxial
-copper ethernet
how can wireless networks be affected by the layout of the building?
the distance from the router, walls and floors can all cause interference
error rate
the number of errors that occur
what causes error rate occur?
due to interference and weak signal
latency
how much time it takes for the data to reach its destination
bandwidth
describes how much data can be transferred over the network in a given time
