1.3 Exchanging Data Flashcards
How does lossy compression work
Unnecessary information is removed
How does lossless compression work
All information is retained so file is replicated exactly and patterns in the data are recorded
What files use lossy compression
JPG - quality is lost
MP3- Frequencies and sounds that can not be heard are removed
What is an entity (databases)
Category of object, person, event or thing of interest to an organisation about which data us to be recorded
What is an identifier (databases)
Uniquely identifies the entity (known as primary key in relational database)
What is the secondary key (database)
Any index that is not the primary key of a table
What are the possible relationship between entities
1-1
1-many
many-many
What is a foreign key (databases)
Links two tables in a relational database
What is a composite primary key (databases)
A primary key that consisted if mire than one attribute
What is an attribute (databases)
An identifying piece of information that serves to define further and expand the primary key
What is referential integrity
Ensuring that a component in tables linked in a relational database are not deleted
What is an index (databases)
Gives the position of each record according to its primary key
One or more secondary indexes may be defined
How is data captured
Manual methods (transcribing) Magnetic Ink Character Recognition
Optical Character Recognition
Smart card readers
Scanners
Barcode readers
How is data selected and managed
Speed cameras
SQL, data may be used to produce reports, send letters or email
How is data exchanged
Electronic Data Interchange
Transaction software processes
What are internet service providers
Connect directly to backbone cables connected by trans continental lines fed across the sea beds and distribute the internet connection to smaller providers who in turn provide access to individual homes and businesses
What is an URL
Full address of an internet resource, it specifies location of a resource on the internet, including resource name and usually the file type so a browser can request it from a website server
What are internet registrars
Hold records of all existing website name names and the details of those domains that are available for purchase
What are internet registries
Organizations that manage and allocate Internet resources like IP addresses within specific geographic regions.
What does the domain name do
Identifies domain that an internet resource resides In.
What is a domain name server
Domain names structured into a hierarchy of smaller domains and written as a string separated by full stops as dictated by the rules of the dns
What are global directories
DNS catalogues all domain names and IP addresses here
Servers can access them to find the correct IP address location for a resource
What happens when a user enters the URL
Browser requests IP address from local DNS
Keeps asking DNS servers till IP address is located
Once it is located a data request is sent by users computer to the location to find the web page data
What is a fully qualified domain name
Includes the host server name
What is an IP address
Unique address that is assigned to a network device, it indicates where a packet of data is to be sent or has been sent from.
What is a router
Use the IP address to direct the data packet
Features of a WAN
Relies on third party connections and are typically spread over a large geographical area
Features of a LAN
Computing devices on a single site connected together by cables.
Can transmit data very fast but only over a short distance
What is a bus topology
All computers are connected to a single cable, the ends of the cables are plugged into a terminator
Advantages and Disadvantages of a bus topology
Inexpensive to install as it requires less cable
If main cable fails network data can not be transmitted
Performance degrades with heavy traffic
Low security, all computers can see all data transmissions
What is the structure of a star topology
Has a single central node, either a switch or computer that acts as a router
What is the role of a switch in a star topology
Keeps record of unique MAC address of each device on the network and can identify the particular computer on the network it should send data to
Advantages and Disadvantages of a star topology
One cable fails, one station affected
Consistent performance
Higher transmission speeds
No data collisions
More secure
Easy to add new stations
Costly to install
If central device fails all nodes can not transmit data
What is WiFi
Local area wireless technology that enables you to connect devices to a network resource or to the internet via a wireless network access point
What is circuit switching
Creates a direct link between two devices for the duration of the communication
Band with is wasted when data is not sent
Devices must transmit and send data at the same rate
Simple to reconstruct message
Electrical interferente could corrupt data
What is packet switching
Method of communicating packets of data across a network on which other communications are happening simultaneously
What is a data packet
Chunks of data that is transmitted across the internet Each contain a header and payload
Include time to live
What is a MAC address
It is assigned and hard coded into a NIC, uniquely identifying the device
What is a protocol
Set of rules defining common methods of data communication
What is HTTP/HTTPS
Hyper text transfer protocol (secure) is a standard protocol for browsers to render web pages
What is TCP/IP
Enables communication with any other computer connected to the internet regardless of its location
What is the TCP/IP stack
Set of networking protocols that work together as four connected layers passing incoming and outgoing data packets
Application layer
Transport layer
Internet layer
LInk layer
What happens in then application layer
Uses protocols relating to the application being used to transmit data over a network
What happens in the transport layer
Uses TCP to establish end to end connection with the recipient computer. Data is sorted into packets with the packet number, number of packets and port number through which the packet should route.
Can request retransmission of lost packets
What happens in the internet layer
Adds source and destination IP address. Routers operate on the network layer and use these to forward packets to its destination
What happens in the link layer
Physical connection between network nodes and adds the unique MAC address identifying the NICs of the source and destination computers
Once received MAC address us stripped off by link layer, which passes packets onto the internet layer which passes them onto the transport layer to remove the port numbers and reassemble the packets
What is the FTP
File transport protocol
Transfers data across a network
Works at application layer using appropriate software
What is a mail server
Routes mail according to its database and it is stored until it can be retrieved
What is the P0P3
Post office protocol
Retrieves emails from a mail server and then deletes it from server
What is IMAP
Internet message access protocol
Keeps email on the server
What is SMTP
Simple mail transfer protocol
Transfers outgoing emails from one server to another or from an email client to the server when sending an email
What is HTML
Language web pages are written in, describes content and structure of a web page so that a browser is able to interpret and render the page for the viewer
What is CSS
Scripting language that is used to describe the layout and styles of a web page
What is java script
Script language that uses all of the same programming constructs that are familiar in languages
Interpreted rather than compiled
Can be used to process input data from a clients computer
What is a client server network
One or more computers (clients) that are connected to a powerful central computer (server)
Advantages and Disadvantages of client server network
Secure
Backups done centrally
Data easily shared between clients
Expensive
Professional IT staff needed
What is cloud computing
Growing service based industry providing access to software or files via the internet using client server model
What is a peer to peer network
No central server and individual computers are connected to each other either locally or over a WAN
Advantages and Disadvantages of a peer to peer network
Cheap
Share resources like printer
Not difficult to maintain
Used for online piracy
