Digital environments Flashcards by Nicholas Basher

What is a batch operating system?

→An OS that doesn’t interact directly with the computer and has an operator that takes similar jobs with the same requirements and groups them into batches to be processed (e.g. bank statement making systems)

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What are the advantages of batch OS’s?

The processors of batch systems know how long the job will take
Multiple users can share the system
Idle time for a batch system is less
Easy to manage large work repeatedly

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What are the disadvantages of batch OS’s?

Hard to debug
Sometimes costly
Other jobs have to wait for an unknown time if any job fails

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What is a time sharing OS?→An OS where each task is given some time to execute

→An OS where each task is given some time to execute so that all tasks run smoothly

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What are the advantages of a time sharing OS?

Each task gets equal opportunity
Fewer chances of duplication of software
CPU idle time can be reduced
Multiple users at once

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What are the disadvantages of a time sharing OS?

Reliability problems
One must have to take care of the security & integrity of programs and data
Data communication problem

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What is a real time OS?

→An operating system designed to process and respond to inputs nearly instantly

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What are the use cases for real time OS’s?

Air traffic control
Airbag systems
Missile systems

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What are the characteristics of a hard real time OS?

Very strict and the smallest delay is unacceptable

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What are the characteristics of a soft real time OS?

Used where the timings need to be less strict
Used in heart monitors (The difference between a microsecond and half a second isn’t going to change reaction speed of a doctor)

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What are the advantages of a real time OS?

Maximum utilization of devices and more output from resources
Focus on running applications and less importance to applications in the queue
Error free
Best managed memory allocation
In an embedded system (usually just a chip or small board)

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What are the disadvantages of a real time OS?

Limited tasks can be run at once
Use heavy system resources
Complex algorithms
Device driver and interrupt signals (needs specific drivers)
Thread priority is not a good idea as they only do one task

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What’s a network OS?

→An OS that runs on a server, providing the ability to manage data

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What are the positives of a network OS?

Highly stable & centralized servers
Security concerns are handled through servers
New technologies and hardware upgrading are easily integrated into the system
Server access is possible remotely from different locations and types of systems

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What are the negatives of a network OS?

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Servers are costly

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User has to depend on a central location for most operations

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Maintenance and updates are required regularly

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Examples of network OS’s→UNIX

Linux

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Software & Peripheral integration

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What is firmware?→Read only memory that controls how a system works

such as how a washing machine works

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What are drivers?→Software/Code that tells the operating system how to interpret the device that is connected

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What is application software?→Software that is made to do a task or set of tasks. Such as Firefox

password managers

What does POST stand for?→Power on self test

How does a BIOS system work?→Non-volatile memory that contains instructions on how the computer should start up. Performs a POST (Power On Self Test) to check all voltages are correct for the components

What does BIOS stand for?→Basic Input Output System

What does CMOS stand for?→Complementary metal oxide semiconductor

Why do computers need a CMOS battery?→To keep time/So the device knows the time & date

What's a zero day attack?→Where the date malware will start attacking a device or set of devices is obscured (like a ticking time bomb but the timer is blurred out)

What's an air gapped network?→A network that is not connected to the internet or any other network in any way

typically needs physical updates carried out through external storage that is checked first

What does NAS stand for?→Network Attached Storage

What's a NAS?→Network attached storage is storage attached to a network that allows anyone on that network with the correct permissions/credentials to access the NAS.

What's a SAN?→A Storage area network is a high-speed network that provides network access to storage devices

Networks

WLAN→Wireless Local Area Network

WPAN→Wireless Personal Area Network

WMAN→Wireless Metropolitan area network

WWAN→Wireless Wide Area Network

What committee/group defines how WLAN's are implemented into the 802.11 standard?→IEE

Who certifies companies to ensure app their products follow 802.11?→Wi-Fi alliance

What are the three signal distortion types?

Absorption - Absorb RF webs killing the Wi-Fi signal

Scattering - Dispersing RF waves by carpet

plasterboard etc.

Reflection - Reflecting waves in another direction (Glass

mirrors)

What are three common transmission methods?

Direct sequence Spread Spectrum - One channel to send data across all frequencies in the channel

Orthogonal Frequency Division Multiplexing (OFDM) - Uses a spread spectrum to increase data rates

MIMO Multiple input Multiple output - Uses DSS and/or ODFM by spreading across 14 overlapping channels at 5MhZ

What are the two 802.11 access modes?

Ad hoc mode - Based on the independent basic service set (IBSS) Setting connections directly to other clients

Infrastructure mode - Designed to deal with security and scalability issues

wireless clients can communicate with each other via an Access Point

What are the two types of service set for 802.11 infrastructure mode?

Basic service set (BSS) ⇒ Clients connect to an AP

allowing communication or LAN-based resources. The WLAN is identified by a single SSID

Extended service set (ESS) ⇒ Two or more BSS’s are interconnected to allow larger roaming distance

the AP’s also share a single SSID

Advantages of wireless networks

Highly mobile

just need to be within a range

Much lower cost to set up a wireless network

fewer resources

BYOD is easy to implement

as the policy can be just for a wireless network

Makes the area look much ✨prettier✨

Simple to install & maintain

Disadvantages of wireless networks

Security can be a concern

as the media to connect is available (WPA2

Slower and somewhat unreliable data transfer speed (interference

number of users)

It can be unreliable and interference is a massive issue

Advantages of wireless networks

Stable & reliable

No interference from other networks

Much faster

Invisible if you don’t know it exists

Easier to instal

Limited set of users

speed stays consistent

Own separate feed (The cable you connect with)

Better security

as the network is all closely monitored

Cheaper to set up than wired

Disadvantages of wired networks

Inflexible and stuck in one place

Can’t easily run cables

May require more time to install

Need to have skills to set up and install a wired network

Maintenance is essential

staff may be needed

Cables get messy very quickly & can get disconnected mistakenly (oh no)

OSI & TCP/IP

What are the layers of the 7 layer theoretical OSI Model?

Application

Most users interact with this

applications

Protocols work with the data the person is using

Supplies to and receives data from layer 6

Presentation

Converts data from one format to another (like encryption & decryption)

Translates the data from the top layer back and vice versa

Transfers to session layer (when)

Session

Starts & stops connections between devices

Starts & stops connections when interrupted

Transport

Transmission of data over networks (speed

where is goes etc.)

TCP & UDP usually

Once completed passed to or received from the network layer

Network

Routing of data

Sends data to the correct location

IP part

Manages IP and MAC addresses

For IP it uses ARP

Data link

Most complex

Packages the data packets

MAC Media access control

LLC Logical Link control

Data passes to or from the physical layer

Physical

Electrical/Physical label (Cables

PINOUTS

Is the device plugged in? Y/N

5V or 0V for cables

What are the layers of the TCP/IP model?

Application

Combines functions of the application

presentation and session layers from the OSI model.

The layer is similar to the transport layer of the OSI model and is responsible fro end to end communication

and error free delivery of data

Transport layer

Exchange data receipt acknowledgements and retransmit missing packet

ensuring that packets arrive in order and without error. Protocols:

TCP→Applications interact together using TCP as they were physically connected

it transmits data in a way resembling character by character transmission rather than separate packets. A starting point that establishes the connection

UDP→Datagram delivery service is provided by UDP. Connections between receiving and sending hosts are not verified by UDP

commonly used by applications that transport small amounts of data

Network layer

Parallel to the OSI network layer

Defines the protocols which are responsible for logical transmission of data over a network.

Main protocols:

IP→Internet Protocol

Responsible for delivering packets from source host to destination host by looking at the IP addresses in packet headers

ICMP→Internet Control Message Protocol

in IP diagrams and responsible for providing hosts with information about network problems

ARP→Address Resolution Protocol

Finds the hardware address of a host from a known IP address. It has various types: Reverse ARP

Network access layer

A collection of applications that require network communication.

Layer is responsible for generating data and initialising connection requests

and manages data transmission

The packets network protocol type (TCP/IP) is identified by the layer

Error prevention and framing are provided (PPP Framing and IEEE 802.2 framing are two examples)

What's the main difference between the OSI and TCP IP models?→TCP/IP is the physical way that computer processes data

whereas the OSI model is the theoretical model. Think

Protocols & Data packet structure

What are network protocols?→A set of rules devices follow to connect over a network

to allow them to communicate

What's a simple definition for data packet autonomy?→In networking

data is bundled into packets of data. They travel around an area

Explain UDP→A connectionless protocol containing no reliability (Best effort

no guarantee

Explain TCP

Every single packet gets delivered (A guaranteed delivery service)

A connection-oriented Layer 4 protocol that provides full-duplex

acknowledged

TCP always operates in full-duplex mode (two independent byte streams travelling in opposite directions)

Data is transmitted in _ _ _ _ _ _ ?→Packets

What is packet switching?→Grouping data into packets that are transmitted over a network

Data in the header is used by networking hardware to direct the packet to its destination

What is circuit switching?→Implementing a telecommunications network where two network nodes establish a dedicated communications channel

known as a circuit

What are the two types of packet switching?

Datagram (The internet)

Virtual circuit

How big is an average data packet?→~1000bytes

What must the control information of a packet contain?

Routing info to tell the data packet where to go

Error detection codes

Sequencing information

Where is the control information in a packet found?→In the packet header and trailer

Advantages of packet switching

Line efficiency

Data rate conversion

Priorities can be used

What is a virtual circuit?→A pre-planned route established before any packets are sent

then all packets take the same route

Virtualisation

What is virtualisation?→The dividing of physical computing resources into a series of virtual machines and operating systems

What is a guest machine?→Another name for a virtual machine running on top of a host machine

which is the main bare metal computer

What is the host machine?→The bare metal machine that virtual machines can be built on top of

How is a virtual machine secure?

Able to control the execution of programs in guest machines transparently

Controlled 'walled off' execution environment

VM manages can filter and control

Resources can be hidden from guest machines

What is aggregation?→A group of separate hosts being tied together and represented to guests as a single host