Networks and security Flashcards
What is a network?
two or more computers - or other electronic devices - that are connected together for the purpose of communication.
4 Advantages of Networks
- easily share files, software and hardware between computers
- Log in from any connected computer and access your data and files
- An administrator can monitor network activity and control security settings
- Data from computers on the network can be automatically backed up on central storage
4 Disadvantages of networks
- initial cost as network devices are required. e.g routers. large companies will need to buy and maintain a server
- A network manager /administrator might need to be employed to maintain the network
- security breaches are more likely and malware e.g. worms , can spread quickly across the network
- If the web server fails , all connected computers won’t be able to access files or log on
what does LAN stand for?
local area network
what does WAN stand for?
Wide Area Network
What does PAN and MAN stand for?
personal area network
metropolitan area network
What does VPN stand for?
virtual private network
What is a local area network?
A LAN has computer systems based geographically close together, usually within the same building or small site, like a school or office
What is a wide area network?
A WAN has computer systems situated geographically distant to each other, possibly across a country or even across the world.
The internet is an example of a WAN that spans the globe
Give an example of a wide area network
The internet is an example of a WAN that spans the globe
What is a personal area network?
A PAN is a personal network for an individual,
/
a network that is spread over a very small area
such as a photographer connecting a smartphone , desktop computer and printer together
What is a metropolitan area network?
A MAN is larger than a LAN but smaller than a WAN and typically covers a relatively large area like a university campus, town or city
what is a virtual private network?
A VPN allows for a secure and encrypted connection to a public network like the internet.
It is often used to protect an individual’s privacy by concealing their real location
Wired connections
wired connections use physical cables, such as copper or fibre optic wires, and require a network interface (NIC) to connect a network
These wired connections use a wired connection protocol - most commonly ethernet
Advantages and disadvantages of wired connections
- faster
- more secure
- NIC required
- restricted movement
Advantages and disadvantages of wireless connections
freedom of movement
WNIC required
slower
less secure
Wireless connections
wireless connections , , use no cables but require a wireless network interface card (WNIC)
such as Wi-Fi or Bluetooth
Wireless connections generally have a slower speed and can be affected by the computer’s distance from the wireless router as well as obstacles like walls or bad weather
What is a data packet?
a file that has been broken down into small chunks of data in order to be transmitted over a network
The main purpose of networking is to share data between computers.
A file has to be broken up into small chunks of data known as data packets in order to be transmitted over a network.
The data is then re-built once it reaches the destination computer.
contents of a data packet (5)
What is the key difference between packet switching and circuit switching
?
a circuit-switched network sends data along the same route.
a packet-switched network sends data packets along different routes
stages of Packet switching
- the data is split into packets
- the data packets are transmitted over a network
- can take different routes to its destination
- when all the packets have arrived the data is reassembled
the internet is an example of a packet-switching network
what is an example of a packet switching network ?
the internet is an example of a packet-switching network
Advantages of packet switching
- transmission is more secure as it is harder for a hacker to intercept complete data because it can take different routes
- if a network device fails the data packets can take an alternative route
- data packets can be sent efficiently and individually across a less busy route
Disadvantages of packet switching
- reassembling the data takes longer because packets may arrive out of order
- it is less reliable than circuit switching as some data packets may not reach the destination ( this is called packet loss)
stages of circuit switching
- when data is transmitted over a circuit - switched network all of the
- data takes the same route to the destination address in one continuous stream
- the data is quickly reassembled at the destination because it is already in the correct order
- the old telephone system is an example of a circuit- switched network
what is an example of a circuit-switched network?
- the old telephone system is an example of a circuit- switched network
Advantages of circuit switching
- reassembling the data is quick because the packets arrive in the order that they were sent
- it is more reliable than packet switching because data is sent in one continuous stream
- the transmission is fast and should encounter fewer errors - once the connection has been securely established
Disadvantages of circuit switching
- less secure as hackers could intercept the data and more easily access the data as it all takes the same route
- establishing a connection takes a long time to set up
- if any device fails on the route then the whole connection breaks and data transfers will be incomplete
what is a network topology?
Network topology refers to layout of computer systems on a network
What are devices in a network topology diagram often called ?
nodes
How does a bus topology work?
- the nodes are connected to a bus (a central cable along which all data is transferred across the network)
- data packets are sent along the main cable (sometimes know as the ‘backbone’) from the source computer to each other systems in turn.
- each system checks the destination address of the data packets
- if the addresses match then the data is accepted otherwise it is passed on to the next system
- terminators are required at both ends of the bus to mark the end of the cable
Advantages of a bus topology?
- because of the simple layout, it is easy to attach another system to the main cable without distributing the whole network
- quick to set up once the main cable has been established making it optimal for temporary networks
- cost effective as it contains less cabling than other topologies and requires no additional hardware
disadvantages of a bus topology?
- poor security as data packets are passed on to each system on the network
- data collisions are likely - this slows down the network
- the main cable will only have a limited length which can become crowded and slows the network speed as more systems are attached. The main cable must also be terminated properly
what is a data Collison?
when two systems attempt to transfer data on the same line at the exact same time.
what network topology is ?
bus topology
how does a ring topology work?
- computer systems are connected together in a simple loop
- packets are transferred around the ring in one direction , passing from one computer system to the next loop.
- as the packet arrives at each computer system, the computer checks the destination address contained in the data packet to see if it matches its own address
- if the addresses match the computer accepts and processes the data packet, otherwise it passes it on to the next system
Advantages of a ring topology
- data collisions are avoided as data packets are transmitted in one direction around the ring
- attaching more systems to a ring topology won’t affect the transfer speed (bandwidth) as the data is transferred at a consistent speed
disadvantages of a ring topology
- if any system on a network fails the whole network fails as the loop is broken and data can’t be transferred to all systems
- to add a new system to a ring topology the network must be temporarily shut down
what network topology is shown?
ring topology
how does a star topology work?
each computer system is connected to a central device, usually a hub or switch
- each computer system is connected to the central hub or switch and transfers its data packets there.
- the hub or switch looks at the destination address and transfers the packets directly to the intended computer
advantages of a star topology ?
- has improved security as data packets are sent directly to and from the hub/switch in the entre
- new systems can be attached directly to the central system so the network doesn’t need to be shut down
- transfer speeds are generally fast in a star topology as there are minimal network collisions
disadvantages of a star topology?
- extra hardware is required to be purchased , installed and maintained
- if the central system fails then the whole network will be unusable until the error is fixed
what network topology is being shown?
star topology
how does a mesh topology work?
- in a full mesh network each computer system is connected to every other computer system
- there is also a partial mesh network where only some nodes are connected to every other node
- data packets are transferred to the destination address along the quickest path , travelling from node to node
- if a pathway is broken , there are many alternative paths that the packets can take
advantages of a mesh topology network?
- if one cable or system fails then data packets can take an alternative route and still reach the destination address
- can usually withstand large amounts of data traffic
- new systems can be added to the network without disrupting the entire topology
disadvantages of a mesh network topology
- the large amount of cables required (especially in a full mesh topology) means the network layout can be expensive to install and maintain
- redundant cabling should be avoided - this is when cables are connected between systems that won’t ever need to communicate
what network topology is being shown?
mesh topology
what is a hub?
a hub receives data packets from a connected device and transfers a copy to all connected nodes
what is a switch?
a switch receives data packets, processes them and transfers them on to the device specifically listed in the destination address of the packet
what is a router ?
routers are used to transfer data packets between networks
- data is sent from network to network on the internet towards the destination address listed in the data packet
- a router stores the address of each computer on the network and uses routing tables to calculate the quickest and shortest path
what is a bridge?
a bridge joins together two networks that use the same base protocols
e.g. a bridge could link together a LAN to another LAN
what is a wireless access point (WAP)
- provides a link between wireless and wired networks.
- it creates a wireless local area network that allows WiFi enabled devices to connect to a wired network
what is a network interface card (NIC)?
a NIC is an internal piece of hardware that is required for the computer to connect to a network
- sometimes known as a network adapter
- wireless network interface cards (WNIC) permit s wireless network connection
what is routing
- a routing table is a list of optimal routes for data packets to be sent from one device to another
- routing tables should be kept accurate and up to date to ensure that packets are transferred as quickly as possible
- during routing the lowest cost route is calculated. this is the shortest path with the fastest nodes to transfer data
what is a protocol ?
a protocol is a set of rules that allow devices on a network to communicate with each other
what is Transmission control protocol (TCP)?
- a protocol that allows data packets to be sent and received between computer systems
- breaks the data into packets and reassembles them back into the original data at the destination
what is internet protocol (IP)?
- protocol in charge of routing and addressing data packets
- ensures data packets are sent across networks to the correct destination
- it is also an addressing system - every device on a network is given a unique IP address so data packets can be sent to the correct computer system
what does HTTP stand for?
hypertext transfer protocol
what is HTTP used for ?
- HTTP is used to transfer web pages over the internet so that users can view them in a web browser
- All URLs start with either HTTP or HTTPS
what is HTTPS?
HTTPS is a more secure version of HTTP that works with another protocol called SSL(secure sockets layer) to transfer encrypted data
-
what is Ethernet ?
Ethernet is used at both the data link and physical layers to describe how network devices can format data packets for transmission
What is WiFi?
WiFi is the main standard for wireless connections
WiFi is actually a brand name that uses a protocol called IEEE 802.11
Another wireless standard is Bluetooth , for short-range data transfer
what does FTP and SMTP stand for?
file transfer protocol
simple mail transfer protocol
what is FTP (file transfer protocol)?
- used to transfer files across a network
- commonly used to upload or download files to/from a web server
what is SMTP (simple mail transfer protocol)?
a protocol used to send emails to a mail server and between mail servers
What is the internet ?
- the internet is a global network of interconnected networks
- the world wide web (WWW) is not the same as the internet.
- It is a way of accessing information, using protocols such as HTTPS to view web pages
What is the internet ?
- the internet is a global network of interconnected networks
- the world wide web (WWW) is not the same as the internet.
- It is a way of accessing information, using protocols such as HTTPS to view web pages
What is a web browser ?
- a web browser is software that uses the HTTP or HTTPS protocol to access and display web pages
Name popular web browsers
google chrome
Mozilla Firefox
Microsoft Edge
What is a URL?
- web pages are accessed by typing a URL (a web address) into the address bar of a web browser
- The URL is the complete address that matches an IP address where the website is stored
- We use URLs as they are easier to remember than an IP address
Why do humans use URLs ?
- We use URLs as they are easier to remember than an IP address
What does URL stand for?
uniform resource locator
structure of the URL :
What does DNS Server stand for
domain name system server
What is a DNS Server?
- stores a list of domain names and a list of corresponding IP addresses where the website is stored
- every web page has a domain name that is easy for humans to remember and type in
Describe the steps taken to display a web page
- a domain name is typed into a browser
- the browser checks a local (cached) host file to check if it already holds the ip address
- if it doesn’t, a query is sent to the local DNS server for the corresponding IP address of the domain name
- the local DNS Server will check if it holds an IP address corresponding to the domain name
- if it does it passes the IP address to your browser
- the browser then connects the IP address of the server and accesses the website
- if the local DNS server does not hold the IP address then the query is passed to another DNS server at a higher level until the IP address is resolved
- If the IP address is found, the address is passed on to DNS Servers lower in the hierarchy until it passed to your local DNS Server and then to your browser
