Mock Flashcards
Describe the main features of a client server network
∆ Controlling computer / network server
∆ Handles the processing requests from the other computers on the network
∆ For resources
∆ And controls security across the network
Describe the main features of a star network
∆ Multiple nodes are directly connected, each via its own cable to the hub/server which is in charge of communication
∆A node sends data to the hub
∆ The hub determines the recipient
∆The hub forwards data to the recipient
Describe the main features of a ring network
∆ The nodes are connected in a loop
∆ Each node is connected to two other adjacent nodes
∆ A special message called a token (data) is passed from node to node
∆ Until it reaches its intended recipient
∆ Data can only travel in one direction
Describe the main features of a bus network
∆ All nodes are connected onto a main cable
∆ Data can be transmitted bi-directional
∆Terminators are used at both ends of the main cable
∆ Each node can transfer data directly to any other node by sending it on the main cable
📝 Evaluate the star topology and the bus topology with respect to data security
⭐️ Network:
∆ Has a central dedicated fileserver, each node is connected directly to the hub by its own cable. The fileserver controls all network communication and the transfer of data packets
∆ The star network is more secure. Data packets are sent from fileserver to node directly via dedicated connection. Fileserver controls all security only intended recipient receives the data packet
🚎 Network:
∆ Has a main backbone to which all nodes are connected, and a terminator at both ends. A node sends a data packet to another node via the backbone
∆ Bus network is less secure. No central control of security, all nodes could access data packets on backbone, data packets travel in both directions
📝 Compare the impact of cable failure on data transmission over a star network and a bus network
∆⭐️ Each device is connected to a central hub by it’s own cable
∆🚎 All devices are connected to a backbone cable
Comparison:
∆ ⭐️ If a cable fails only a single device is affected
∆ 🚎 If the backbone fails all communication is affected, if a connecting cable fails only that device is affected
Why are communication standards required?
∆ To enable different hardware devices to pass data to one another
∆ securely and coherently
∆ using agreed formats
Describe the main features of the Open Systems Interconnection (OSI) model
The OSI model:
∆ Consists of an abstract model of networking and a set of specific protocols
∆ It defines a layered protocol (7 layers)
∆ Each layer deals with specific functionality
∆ Control is passed from one layer to the next
∆ Each layer interacts directly only with the layer immediately beneath it and provides facilities for use ny the layer above
Describe the Data Link layer of the OSI model
∆ Deals with functions such as error detection, correction and creating data blocks
∆ Converts each outgoing packet into a series of bits
∆ Interacts with the network/physical layers
Describe the application layer of the OSI model
∆ Presents information to the end user
∆ Deals with functions such as data transfer, messaging, operating system functions, end user interface
∆ Interacts with the presentation layer
Briefly describe the TCP/IP protocol.
Transfer Control Protocol / Internet Protocol supports connectivity between LANs and WANs. It allows all Internet users and providers to communicate irrespective of the hardware. Providers have unique addresses.
Describe the purpose of the IP Layer
∆ Delivers the data packets to the appropriate node using the IP address
∆ Treats each data packet independently
Describe the purpose of the TCP layer
∆ Enables two hosts to to establish a connection and exchange data. It is responsible for reliability and correct delivery
∆ It converts a message into data packets containing destination address
∆ That is transmitted over a network to the destination computer
∆Then is reassembled so that the message can be read by the recipient
Describe the main features of RFID technology
∆ Data relating to a product is stored on an RFID tag attached to the product
∆ RFID tag contains data programmed into small computer chip
∆ Tag activated by radio waves emitted from RFID reader
∆ Tag sends data stored in its memory back to the reader
∆ Active or passive technologies
Describe checksum as a method of error detection method
Calculated by adding together all the bytes to make a block of data eg. of 256 bytes
Checksum is recalculated after data transmission
If the recalculated checksum is different there has been an error
Some types of checksum may automatically correct error.
Evaluate the use of parity bits in error detection
An additional bit is calculated from the other bits in a byte, set to make total number of bits odd or even. The parity bit is checked after data transmission and compared to original, if they are different an error has occured and retransmission is requested
What is CRC
A special type of checksum applied to a block of data
An algorithm is applied to block and checksum applied to block
Recipient applies same algorithm and checksum and compares to already appended result
If they do not agree data has not been received correctly.
Retransmission requested
What is echo checking?
When data is received and a copy sent back to transmitter
Where it is compared with original
If it differs from original it is transmitted
Echo checking is an automatic process
Describe the main features of fibre optic cable
Fibre optic uses light to transmit info rather than electric signal
Cable consists of multiple strands of glass fibre inside an insulating casing
Light is transmitted in pulses difficult to intercept
Cable length can vary from short to long
Signal difficult to intercept without destroying
High bandwidth
Flexible can be used in awkward layout
Describe main features of wifi
WiFi enables two or more devices to be connected wirelessly for data sharing. A computer with a wifi network card can connect wirelessly to a router over a limited distance
A wifi network can either be open or closed
An area with wireless access is called a wireless hotspot
Describe the main features of Bluetooth technology
It uses radio waves to send info between two devices in close proximity to each other which have been paired
It is a protocol.
What is bandwidth?
Measure of capacity of a communication channel. Range of frequencies a channel can handle at any one time. Given as frequency (range) or transmission rate - bits per second
What is broadband?
Term used to mean any high speed internet access that is always on and faster than traditional dial up. Uses physical connection of telephone system
Broadband is wide bandwidth data transmission which transports multiple signals and traffic types.
Describe the main features of metal cables
Copper wires are used to transmit electronic signals
The wires are encased by a layer of insulation
High transmission speeds and cheap costs of insulation
Cable only can be used over short distance
Susceptible to radio and electronic interference
Referential Integrity
If a foreign key is used it must correspond to an existing primary key
Entity
An object about which data is stored
Foreign Key
A primary key is one entity which appears as a non-key in another entity as a link
Composite Key
Consists of more than one attribute which uniquely identifies an entity occurrence
Lookup
Attributes described as lookup are restricted to a list of values
The desired value is selected from list
Attribute
Describes a data item within an entity
ER modelling
Uses ER diagram to represent real world objects and links between them.
Normalisation
The technique of organising data in the database to eliminate problems such as data redundancy and data inconsistency and improving data integrity
1NF
if all attributes are atomic and entities do not have repeating groups
2NF
Data in 1NF and non key attributes are dependant on primary key
3NF
Data in 3NF and there are no non key dependencies
Logical Data Modelling
Produced during design of the database
It identifies entities, relationships between entities attributes for each entity and keys for entities
Physical Data Modelling
Produced during implementation
Creates table structure, field names, data type of each field, keys for each table, validation rules
QBE
Query By Example, allows user to search criteria by selecting an option from list or by entering value in text box
Less expertise required than SQL
Primary Key
An attribute which uniquely identifies an entity
Main features of a relational Database
Data is stored in tables, consisting of records
Each record uniquely identified by primary key
Tables are linked via primary and foreign keys
Advantages of Relational over Flat File Database
Data redundancy minimised - As non key data entered once, reducing file size
Data consistency ensured - Attribute cannot have conflicting values
Flat File Database
Database in which there is a single file not linked to any others
Data Indépendance
Data kept separate from programs which use it
Data Integrity
Refers to the correctness of data can be affected by input errors
Minimised by data verification
Data protected from accidental or deliberate modification
Data Consistency
Attribute has only one value at a time in a database
