1.3.3 Flashcards
network
connecting at least one computing device to another, either via cable or wireless
advantages of networks
Users can share files
Users can share peripherals and connections to other networks such as the internet
Users can access files from any computer on the network
Servers can control security, software updates and backup of data
Communication with other people – e.g., email and social networking
disadvantages of networks
Increased security risks to data
Malware and viruses spread very easily between computers
If a server fails, the computers connected to it may not work
Computers may run slower if there is a lot of data travelling on the network
standards
a set of hardware and software specifications that allow manufacturers to create products and services that are compatible with each other
protocols
if 2 devices share the same protocol, they can exchange information
common protocols
TCP - Communication over LAN/WAN
IP - Communication over LAN/WAN
UDP - Communication over LAN/WAN
HTTP - Web page requests
HTTPS - Web page requests
FTP - File tansfers
POP - Email
IMAP - Email
SMTP - Email
importance of protocols and standards
most devices wouldn’t be able to interact or communicate with one another
TCP/IP stack vs UDP
Transmission Control Protocol - provides error-free transmission between two routers
Internet Protocol - routes packets across a WAN
TCP + IP make the stack that is foundation for communication over the internet
User Datagram Protocol - uses a simple, connectionless transmission model
used to send short messages using datagrams, where speed is more important than accuracy
an alternative to TCP but has no error checking
HTTP(S)
Hypertext Transfer Protocol - a way for a client and server to send and receive requests and deliver HTML web pages
the fundamental protocol of the WWW
Hypertext Transfer Protocol Secure - HTTP, except it adds in encryption and authentication
FTP
File Transmission Protocol - used for sending files between computers, normally on a WAN
POP/IMAP/SMTP
Post Office Protocol - retrieves emails from a mail server and transfers them to your device, removing them from the server in the process
Internet Message Access Protocol - keeps emails on the mail server, maintaining synchronicity between devices
Simple Mail Transfer Protocol - transfers outgoing emails between servers and from email clients to servers
the internet
the most well-known WAN
a collection of interconnected networks, routers, cables, satellites and other hardware spanning the world
Remember, the internet is not the same as the World Wide Web, which is just a service on the internet
WWW
a service on the internet
DNS
Domain Name System - turns domain names into IP addresses, which browsers use to load internet pages
protocol layering
to divide the complex task of networking into smaller, simpler tasks that work in tandem with each other
hardware and/or software for each layer has a defined responsibility, and each one provides a service to the layer above it
advantages of layering
Reducing a complex problem into smaller sub-problems
Devices can be manufactured to operate at a particular layer
Products from different vendors will work together
4 main TCP/IP protocol layers
Application
Transport
Network
Link
application layer
Network applications such as web browsers or email programs operate at this layer
uses an appropriate protocol relating to whatever application is being used to transmit data
tansport layer
Sets up communication between two hosts – they agree settings such as language and packet size
internet/network layer
Addresses and packages data for transmission
Routes packets across the network
link layer
Network hardware and connection port standards
Operating system device drivers also sit here
Facilitates the transmission of binary via any media
LANS
Local Area Network - a network that covers a small geographical area, typically located on a single site
All the hardware for a LAN tends to be owned and controlled by the organisation using it
LANs are typically connected using: UTP cable, Fibre optic, Wi-Fi
WANS
Wide Area Network - a network that covers a large geographical area
When multiple LANs physically located in different areas are connected, they form a WAN
The infrastructure that connects LANs to form a WAN is leased from telecommunication companies who own and manage it
WANs are typically connected by: Telephone lines, Fibre optic cables, Satellite links
circuit switching
provides the basis for traditional telephone networks
creates a temporary and dedicated link of fixed bandwidth between the source and destination that only lasts until the transmission is complete
guarantees the quality of the transmission through dedicated bandwidth, making circuit switching excellent for data that needs a constant link end-to-end such as real-time video
however a lot of the potential bandwidth can be wasted
packet switching
breaks streams of data into smaller blocks, each sent independently of one another
at each node, packets are sent via whichever route the node decides is the least congested – this maximises bandwidth but doesn’t guarantee the quality of the transmission
packets can take different routes to their destination and may arrive out of order
more affordable and efficient than circuit switching as all bandwidth can be used at once
requires less complex infrastructure and can easily respond if parts of the network fail
network threats
viruses
worms
hackers
denial of service
data interception
phishing
spyware
network security
The aim of network security is to:
Only allow authorised users access to what they need
Prevent unauthorised access
Minimise the potential damage caused by unauthorised access
virus
pieces of code capable of copying themselves and spreading throughout a system
typically designed to corrupt a file system or destroy data
spyware
a form of malware that covertly obtains information about a user’s computer activities by transmitting data from their device
denial of service attack
when an attacker floods a server with useless traffic, causing the server to become overloaded
(past attacks exploited limitations of the TCP/IP stack)
attacks often target web servers of high-profile organisations such as banks, large-scale e-commerce businesses and the government
attacks do not typically result in the theft or loss of data or other assets, they can cost a great deal of time and money to handle
anti malware
software to prevent/minimise the impact of malware
proxies
a physical device placed between a network and a remote source
all traffic travels through the device on its way in and out of a network
looks at the page and its contents and choose whether to pass it back to the user or not
ensures there is no direct, physical connection between a single user and a remote source
encryption
turning plain text into an unreadable form
encrypted using an algorithm and a unique key
you can only translate it with the appropriate key
(won’t stop you from being hacked, but it will make any stolen data very difficult to read)
firewalls
a piece of software or hardware (sometimes both) configured to let only certain types of traffic through it by blocking certain ports and types of traffic
it can also inspect data travelling across it to see if it looks suspicious
network hardware
Modem
Router
Cable
Network interface controller (NIC)
Wireless access point (WAP)
Hub
Switch
modem
transforms digital info from your computer into analogue signals to be transmitted through wires an vice versa
most modems have 2 ports:
One that connects to the outside world.
An Ethernet port that connects to a computer or router
router
mainly responsible for routing data:
Between devices on a small home network.
Between devices on a network and the internet.
modems connect to one port on the router, often labelled WAN. Your devices connect to the other ports or wirelessly using the Wi-Fi standard
DoS vs DDoS
DDoS (distributed denial of service) attack occurs when multiple systems orchestrate a synchronised DoS attack against a single target
cables - types
The 3 most popular are:
Twisted pair
Coaxial
Fibre optic
SQL
a code injection technique used to attack data-driven applications
designed to exploit vulnerabilities in poorly coded database applications
code is entered into input text boxes and is then executed by the server
cables - twisted pair
made of a pair of insulated copper wires
can be affected by noise from external magnetic fields, but most affordable
Only able to provide low bandwidth, generally used for telephone networks, data networks and cable shielding
cables - coaxial
made of 4 cylindrical components – (in to out) solid conductor wire, insulation, grounding conductor, exterior insulation
can be affected by noise from external magnetic fields but to a lesser extent than twisted pair
moderate bandwidth, but more expensive than twisted pair but cheaper than fibre optic
used for feedlines that connect radio transmitters and receivers to antennas, as well as computer network connections, digital audio and cable television
cables - fibre optic
made of very thin optical fibres bundled together into a single cable (glass or plastic)
the highest noise immunity, as the light rays are unaffected by electrical noise
high bandwidth capabilities, most expensive
used to support long-distance connections between cities and countries, as well as data centres and organisations transmitting large volume of data
NIC
Network Interface Controller
connects a computer to a network
allows wired and wireless communications between computers on a LAN or connected to a large-scale network using the Internet Protocol
a physical layer and data link layer device, providing the necessary circuitry for physical layer processes and some data link layer processes to run on it
hub
allows you to connect multiples devices to 1 network
operates on the physical layer and considered a passive device (clarifier)
con - the network can easily become flooded with unnecessary traffic
purely a hardware device
typically slower than switches in terms of data transfer
pd - broadcasts transmissions it receives to all connected devices
switch
allows you to connect multiples devices to 1 network
operates on the data link layer and is an active device (clarifier)
A switch typically has software installed on it for administration and configuration purposes.
Switches are typically much faster than hubs in terms of data transfer.
ad - inspect transmission & route them to right device keeps traffic low
WAP
Wireless Access Point
a device that creates a wireless local area network (WLAN)
connects to a wired router/switch/hub via an Ethernet cable and projects a Wi-Fi signal within a designated area
Wi-Fi range is limited and easily interrupted by various construction materials, so most businesses use multiple WAPs for full coverage.
client-server - pros
Easier to manage file security.
Easier to back up shared data.
Easier to install software updates to all computers.
client-server - cons
Can be expensive to set up and maintain.
Requires IT specialists to maintain.
The server is a single point of failure.
Users will lose network access if the server fails.
client-server
Controls access and security for a shared file store.
Manages access to the internet.
Manages printing jobs.
Provides email services.
Runs regular backups of data.
client-server
Controls access and security for a shared file store.
Manages access to the internet.
Manages printing jobs.
Provides email services.
Runs regular backups of data.
peer-to-peer
A peer is a computer connected to the network.
A peer is equal to all other peers.
Peers serve their own files to each other.
Each peer is responsible for its own security and data backup.
Peers usually have their own printers.
Peers can send print jobs to another peer to process, but that peer must be switched on to communicate with the printer.
peer-to-peer - pros
Very easy to maintain.
Specialist staff are not required.
No dependency on a single computer.
Cheaper to set up.
No expensive hardware.
peer-to-peer - cons
The network is less secure.
Users will need to manage their own backups.
Can be difficult to maintain a well-ordered file store.
ISP
internet service provider
