Computer networks, connections and protocols Flashcards
What is a stand-alone computer?
A computer not connected to another
What is a network?
More than one computer system connected together allowing for communication and sharing of resources - hardware, software and data
What is the internet?
A worldwide collection of networks. (A network of computer networks).
Using the same protocol
This is called IP, or Internet Protocol
Use packet switching to transmit data.
It is the largest WAN in the world.
What are the advantages of having a network?
share data very easily
work collaboratively
share device, e.g printers
share single internet connection
What is a LAN?
Local Area Network
Confined to a single geographical area
Infrastructure normally owned by the user
Examples: home, school
What are the advantages of a LAN?
Share and exchange of information e.g updating databases
Data and software can be held anywhere and can be accessed anywhere
Device sharing - save money
Security
Software sharing and mainetnace
Data is easy ot back up as it is stored centrally on the server
LAN has its own infrastructure/cables/network
What are the disadvantages of a LAN?
Expertise needed - complicated to manage outsourcing (e.g the school uses the company Eduthing)
Need for increased security - viruses may be able to infiltrate the network and infect every computer
What are the different hardware required to connect a stand-alone computer to a LAN?
NIC, Router, Switch, Transmission media, WAP
What is a WAN?
WAN is a Wide Are Network
Covers multiple geographical areas
A LAN connected to other LANs
A network with multiple sites e.g network of world wide branches of a business
WAN uses external hardware/infrastructure/cables/network e.g supplied by BT
What does a WAN uses to connect two or more remote locations?
cables, telephone lines, satellites or radio waves
What are some organisations that might use a WAN?
organisations such as universities and schools may have a no. of geographical locations (each one will have its own network, when these networks are joined together they create a WAN)
Large companies with many offices e.g banks
Governments which have employees in many locations
Research organisations which are located in more than 1 place.
What is a Network Interface Card? (NIC or WNIC)
Hardware which contains circuits which allow computers to communicate over a network either using cables or wirelessly
Usually integrated on motherboard of a computer
assigned a unique MAC address
What is a router and what are its tasks?
A router sends data between networks. It connects networks to the internet using IP addressesYou cannot connect to a WAN without using a router.A router uses IP (internet protocol) addresses to control traffic.
Tasks:
- receives packets of data from a network/internet
- (uses routing table to) decide where to send packets
- forwards packets of data from one network to another in the most efficient way
- it assigns IP addresses to machines
What is a switch?
Allows multiple devices to connect to each other in a LAN.
Sends and receives data between computers on a LAN
Device learns the MAC address (hardware address) of the computer connected to each port
Inspects destination address of data packets coming in
Sends packets of data to the correct recipient directly based on their address
Buhs, by comparison, will send the data to all the connected computers
What are the similarities and differences between a router and a switch?
Similarities:
both connect devices
receive data from devices
transmit data to its destination
Differences:
switch uses MAC addresses
Router uses IP addressses
S connects computers in a LAN
R connects networks to the internet/different networks in a WAN
R stores IP addresses of devices attached in routing table
S looks for correct MAC address before sending
What is ethernet?
Standard communications protocol embedded in hardware devices: ethernet describes how devices should format data ready for transmission between computers on the same network.
Basically a standard for networking technologies.
used for building wired LANs
ethernet cables connecct NIC in a device to central switch/hub
higher bandwidth available for a cost
What is transmission media? What is unbound and bound transmission media?
Transmission media:
The way the communication is sent through a network.
Bound - uses physical links e.g cables to transmit information
Unbound - no physical links: uses microwave, infrared or radio signals to transmit information
What are the benefits of using copper cables (UTP - unshielded twisted pair) for transmission media?
Connections between desktop computers and a switch or a router are usually achieved with a wired connection
- wired connections ensure maximum bandwidth, security and reliability
- UTP the wires a twisted aroudn each other to reduce interference
- normally there is a set of wires for transmission and a set of wires for receiving
- the grade of copper and insulating material affects the quality of the overall cable and therefore bandwidth
What are the advantages of using fibre optic cables as transmission media?
uses light to transmit data
cover much longer distances and greater bandwidth than copper due to reduced interference
the backbone of the internet uses fibre optic cables
used in high-traffic connections such as between switches and remote buildings
Describe a star network topology.
Most popular wired type of network
central switch
all devices connected to central switch
the switch is intelligent and makes sure traffic only goes where it is intended
if a single cable breaks only that computer is affected
the switch however is still a serious single point of failure
What are the advantages and disadvantages of a star network topology?
Advantages
Fast transfer data as there are fewer data collisions
if one cable fails the other workstations are not affected
disadvantages
requires additional hardware such as a central switch
if the central device fails the whole network goes down
Describe a full mesh topology.
Every device is connected to every other device
What are the advantages and disadvantages of a full mesh network?
advantages
no single point of failure - it is a self healing network
expansion and modification can be done without disrupting the network
data can be transmitted from different devices simultaneously
disadvantages
can involve redundant connections
expensive to install cabling if using wired connections
network mainetnance and administration is difficult
Describe a partial mesh network topology.
Multiple routes exist between different devices
however every device is not connected to every single other device
a compromise solution which lowers the amount of hardware needed compared to a full mesh network
What are the disadvantages of networking?
increased security risks to data as it’s now shared
malware and viruses can spread very easily between computers
if a central server fails ,the computers connected toit may not work
the computer may rune more slowly if there is a lot of data travelling on the network (traffic)
What are the 11 things that affect the performance of networks?
Bandwidth available
Number of users at the same time
Transmission media
Latency
Error rate
Interference, e.g thick walls
Applications being used
Distance to travel/signal strength
Server/CPU performance
Number of data collisions
Amount of data to transfer
What is bandwidth?
Bandwidth is the amount of data that can be sent and received successfully in a given time
Not a measure of how fat data travels, but HOW MUCH data can be sent on the transmission media
Measured in bits per second, called bit rate
How does the number of users affect the performance of networks?
Too many users or devices on the same network can cause the network to slow down if there is insufficient bandwidth for the data
How does transmission media affect that performance of networks?
Wired connections have a higher bandwidth than wireless connections
Fibre optic cables have a higher bandwidth than copper cables
How does error rate affect the performance of networks?
Less reliable connections increase the number of errors that occur when data is transmitted
this means that data needs to be resent until it arrives correctly
the signal quality of wireless conecctions is dependent on the range of devices from the wireless access point and other environmental factors (like a wall)
the signal quality of copper cables is determined by the grade of material used which reduces interference
the lenght of the cable is also a factor
Basically, the more errors there are, the more times data has to be resent until it is correct, meaning slower performance
What is latency and how does it affect the performance of a network?
Latency is the length of time a packet of information takes to travel through a network.
aka the delay frm transmitting data to receiving it
latency is caused by bottlenecks (when one component htis its limit, impeding the capacity of other components like a limiting factor) in the infrastrucutre of the network
For example, by not using switches to properly segment traffic on a network
hardware such as switches and transmission media may not operate at the same speed.
What are the clients and servers in a client-server model?
In a client server model, there is a client computer and a server.
The server is a powerful computer which provides services or resources required by any of the clients.
The client is a computer or device that requests the services or resources provided by the server.
Both LANs and WANs can operate either with or without a server.
What does a client-server model do?
A server controls access and security to one shared file store.
A server manages access to the internet.
A server manages printing jobs
A server providesemail services
A server runs a backup of data
A client makes requests to the server for data and connections
In a school for example, there may be dozens or even hundreds of clients, and several servers (like a file server, printing server etc.)
What is the role of a server and a client in a client-server model?
Client:
Sends a request to the server
waits for a reply
receives a reply
Server:
waits for requests from client
performs any processing required to fulfill the request
the request data is sent back to the client
What are the advantages and disadvantages of a client-server model?
Advantages
- The network can be controlled centrally from the server so it is easier to backup data and update software (to all computers)
- The network allows for improved scalability, meaning more clients can be easily added to the central server
- Hardware, software, and resources can be shared across the network, such as printers, applications, and data files.
disadvantages
can be expensive to set up and mainatin
requires IT specialists to maintain
the server is a single point of failure - users will lose access if the server fails
What is a peer-to-peer model?
A peer-to-peer network is one where data is shared directly between systems without requiring a central server.
A peer is a computer on a network, and is equal to al other peers
Peers serve their own files to each other
Each peer is responsible for its own security
each peer is responsible for its own backup
peers usually have their own printers
you can send print jobs to another peer to process, but that peer would need to be switched on to be able to communicate with the connected printer
suitable for small companies with fewer computers
no central server controls files or security
all computers can easily see files on all other computers
all computers can communicate with each other without going through a server
Optimal for sharing files that can then be downloaded.
What are the advantages and disadvantages of a peer-to-peer model?
Advantages
- Very easy to maintain
- No specialist staff is required
- No dependency on a single server/device
- Cheaper to set up, as no server is requried.
- No expensive hardware required
- Individual computers can share a router, printer, modem and other hardware
- Users can communicate directly with each other and share each others’ files
- Clients are not dependent on a server
Disadvantages
- Users will need to manage their own backups as without a dedicated server there is no central device to manage security or backups. This means that each device needs its own backup system too
- Can be difficult to maintain a well-ordered file store
- Network is less secure, as viruses and malware are more easily transferred over this network as there is no central firewall
- If a computer is switched off, data from that machine cannot be retrieved from other machines
- Computer performance will decrease with more devices connected to the network, especially if other machines are slow.
What is hosting in general?
Hosting is the storing of files and data on a web server. The web server is referred to as a host.
The host name contains 3 different hierarchical levels (e.g. bbc.co.uk) and works in reverse - UK is biggest, very generic, 2nd is usually the type of organisation e.g. co, org, sch etc. and the 3rd is the name of the organisation. Together, unique domain names can be created.
What is web hosting?
Web hosting is a service offered by companies that will host web pages and files for websites.
The web hosts will often provide database servers.
Companies that provide more general hosting, such as backup servers, are known as hosting service providers
What are the advantages of hosting?
Web hosts have far more bandwidth - so they can serve more users
Web hosts are able to monitor their equipment 24 hrs a day
Web hosts will back up websites remotely
What is a domain name?
A domain name is a human readable name for a resource on a network.
A domain name service (DNS) is made up of multiple Domain Name servers. Describe how a browser retrieves and displays web pages, including the use of DNS.
Send URL to local DNS server for IP address of the URL.
Hierarchy of DNS servers - if not local, goes to a DNS server further out (a bigger one), then back (through each DNS server)
when they work out the IP address, they send it back to the browser
web browser requests web server for webpage, using IP address
web server sends back the page
ONLY BROWSER CAN DISPLAY WEBPAGES.
What is the cloud?
The cloud is a term used to refer to services that are delivered over the Internet. It is a remote service provision (e.g. storage, software, processing)
What are the advantages and disadvantages of using cloud?
Advantages
You can access your data and applications from anywhere at anytime
It is less expensive: you don’t need a powerful computer with a huge hard drive - everything is stored and run on a remote computer
Backing up data is no longer crucial - it can be done by service provider
Disadvantages
Personal data will be stored on another company’s computers
If the Internet connection is lost, often the service becomes unstable
Slow Internet connections may result in a poor quality of service
Although most services will backup data stored with them, it is easy for people and organisations to see how resilient this is
What is the World Wide Web?
A collection of linked hypertexted documents
What is a protocol?
A set of signals, codes and rules that control communication between devices
TCP/IP is the most important for looking after data transfer
What is a MAC address?
A MAC (Media Access Control) Address is a number used to identify a device that potentially can be on a network.
What is an IP address?
An IP address is a unique number used to identify the location of a device connected to a network/internet
What’s the difference between MAC addresses and IP adresses?
MAC Address:
Doesn’t change if you change the location of your device (e.g going to another country)
Assigned by manufacturer of the device
physical address
IP address:
Determines the actual geographical location of a networked device
May be assigned by your ISP (internet service provider)
Logical address
What are the advantages of packet switching?
Network failures don’t stop the message
Advantage taken of unused connections
What is encryption?
Encryption is the encoding of data so that it can no longer be easily understood
2.4 GHz of wifi frequency over 5GHz of wifi frequency and vice versa
2.4 GHz - wider range, is better at covering larger distances, but slower transmission rate, better transmission rates through walls and objects, but more interference from other devices
5GHz - faster data transmission, better for streaming videos , less crowded space with 23 non-overlapping channels as opposed to just 3, but shorter range so less able to penetrate through walls -need for extender device, and fewer devices can use this frequency
What is a standard?
Standards are a set of specifications for hardware and software.
What are the different protocols used for?
TCP (transmission control protocol)- provides error free transmission between two routers
IP - routes packets across a WAN
TCP/IP protocol stack - important for data transfer across internet
HTTP/HTTPS hypertext transfer proctol (secure) - client-server method of requesting and delivering HTML web pages, but HTTPs is secure, as it uses encryption and authentication, and is used when sensitive information needs to be transferred like passwords
FTP - file transfer protocol - used for sending files between computers, usually on a WAN
POP post office protocol - retrieves emails from a mail server - removes it from server and transfers to your device
SMTP - simple mail transfer protocol - sends mail to an email server
IMAP - internet message access protocol - used by mail clients to manage remote mail boxes and retrieve email from a mail server
What are the advantages of using layers?
independent - changes can be made to one layer without affecting the others
self contained - do a specific job, so those writing them need to have specialist knowledge in that layer only
makes it easier to have standards for each individual layer
Where is a website hosted?
A website is hosted on a Web server.
What are computers that access websites called?
clients
What is a DNS server?
A DNS server stores a list of domain names and a list of corresponding IP addresses where the website is stored.
A Domain Name Service is made up of multiple domain name servers.
How does a computer display a webpage/user gain access to it?
- A domain name/URL is entered into a web brower.
- The web browser sends a request to the local Domain Name Server for the matching IP (Internet Protocol) address.
- If the DNS server finds a corresponding IP address, the IP address is sent back to the web browser.
- The web browser requests the web server for the webpage using an IP address.
- The web server sends back the webpage.
If the local DNS servre cannot find a matching IP address, then the request is passed to another DNS server at a higher level until the IP address is found. If the IP address is found, it is passed on to DNS servers lower in the hierarchy until it is passed to your local DNS server and your web browser.
Why is encryption (of a network) needed?
- So that encrypted data cannot be read if you don’t have the key, so only authroised users can see the data
- It is required to encrypt data as stated by DPA
- so that only authorised users can gain access to the data (kinda point 1)
Why is Ethernet a standard?
- all manufacturers use ethernet, so no matter you you by ethernet from the internet will work.
What are the advantages of using wireless connections in a network?
- You can move around freely and easily connect to the network where there is a signal
- You can move devices around as no need to plug devices into sockets
- Fewer cables are used, so it’s cheaper and easier to set up (installing less sockets in the house)
- Easier to add more devices e.g. phones, laptops etc.
- Less hardware means less tripping hazards
WNIC required
What are the disadvantages of wireless networks?
- A wireless connection is less secure than a wired connection, as wireless connectiosn can be hacked into more easily.
- Speeds of a wireless connection are slower as obstacles can easily interrupt connection
What is a network topology?
A network topology refers to the layout of computer systems in a network.
What is the concept of data packets?
When sending data across a network, files are broken down into smaller parts called data packets. They allow data to be transferred quickly as whole files are too large to be transferred as one unit. Each packet of data is redirected by routers across networks until it arrives at its destination. Data packets may be split up and use alternative routes to reach destination address. When the data packets have arrive the packets are reassembled back into the original file.
What are the different servers and what do they do?
File server: holds all the data files and databases and manages backups.
A print server may organise printing on different printers.
An email server may receive emails, detect and block spam, distribute emails to users
A web server may host the school’s external website.
A database server may host student records.
What are the hardware required to connect stand-alone computers in a LAN?
Wireless access points, routers, switches, Network interface card, transmission media
What is a wireless access point? What are its functions?
A wireless access point provides a link between wireless and wired networks. It creates a wireless Local Area Network (LAN) that allows WiFi-enabled devices to connect to a wired network.
Examples in a public area inlude wifi or bluetooth hotspot, e.g. a wifi hotspot in a coffee shop or airport to provide access to the internet.
A WAP can be a separate device or built into another device such as a router.
What are the three common types of transmission media?
- Fibre optic cables: very fast but more expensive and fragile cables typically used to send data quickly across a WAN. Data is sent as pulses of light.
- Ethernet cables: cables typically used in a LAN to transfer data between nodes and hardware such as switches.
- Coaxial cables: older, slower copper cables that aren’t used as much now because they are affected by strong electromagnetic interference. (NOT a UTP cable).
What is a node?
Any device connected to a network.
What are the advantages of a wired network?
Wired connections use physical cables, such as copper or fibre optic wires, and require an NIC to connect to a network. They mostly use a wired connections protocol called ethernet.
- They have generally faster data transfer than wireless networks
- You are much less likely to suffer interference in a wireless network
- More difficult for unauthorised users to intercept data.
What are the disadvantages of a wired network?
- They are expensive to reinstall or reconfigure
- Users can’t install move a device from one location to another as there may not be a network connection available.
When is a wireless network used?
Wireless networking has seen an increase in popularity because it is easy to connect a node to a network. Many different types of device, such as laptops, tablets, smartphones, interactive TVs, media centres, games consoles and security cameras, can easily connect to a network when needed, without having to run a cable to each device.
Wireless networks give freedom of movement. They are therefore popular in homes, schools and any organisation that has a constantly changing number of connected nodes.
When is a wired network used?
Wired networking is still widely used in businesses or schools where devices such as desktop computers are unlikely to need to be relocated very often. Tasks that require large amounts of data to be accessed from
servers
- such as commercial video editing - are likely to be quicker using a wired network as the bandwidth available to each connected device is much larger.
Many organisations run both a wired and wireless network, allowing flexibility on the types of device used depending on the need of the user.
How is an IP adress formatted?
There are two versions currently in use - IPv4 and IPv6
IPv4: 32-bit address, represented in denary, allows for over 4 billion unique addresses.
Four 8-bit segments of denary values, ranging between 0-255. Separated by full stops.
Example:135.13.218.102
IPv6: 128-bit address, represented in hexadecimal, allowing for an undecillion unique adresses.
It has eight 16-bit segments of four hexadecimal values (ranging from 0000-FFFF) separated by colons.
Example: 736E:1029:A4B3:902D:77B2:72FF:AE62:0912
What is a MAC address and how is it formatted?
A MAC (Media Access Control) address is a unique hexadecimal number assigned to each network interface card/controller inside a networked device such as a laptop or router.
It is a 48-bit address made up of six 8-bit pairs in hexadecimal, separated by dashes.
MAC example: 19-C2-D1-47-AA-38
What is the point of a standard?
It provides rules for areas of computing.
Standards allows hardware/software across different manufacturers/producers.
It makes it possible for manufacturers and produces to create products and services which are compatibele with each other. Without standards most devices wouldn’t be able to successfully interact or communicate.
Character sets like ASCII are character set standards.
HTML - standards for creating websites.
What is a layer?
A layer is a division of network functionality.
What is TCP/IP?
TCP/IP is a set of protocols that operate on different layers. These two protocols are used together to allow computers to communicate on a network.
What is a client-server model? (simple answer)
Clients make requests to a server, the server anages that request and responds.
What are the differences between a client server and peer to peer model?
