Networks Flashcards
(69 cards)
1
Q
What is a computer network?
A
Two or more computers connected together to communicate to exchange information and data.
2
Q
What are the advantages of computer networks?
A
- share software stored in the main system
- files can be easily shared between users
- can communicate via email, instant messenger and VoIP (voice over IP)
- more straightforward to back up data
- data can be transmitted to remote areas that are connected to local areas
- allow sharing common peripherals (e.g. printers) = save money
3
Q
What are the disadvantages of computer networks?
A
- cost of purchasing cable to construct a network as well as file servers = costly
- management is complicated - needs training and a specialist network manager
- files in server become inaccseible if server breaks down
- if a virus gets into the system = spreads easily through a network
- vunerable to hacking esp with WANs = need firewall
4
Q
What are the 3 main types of networks?
A
- Wide Area Networks - WANs
- Local Area Networks - LANs
- Personal Area Networks - PANs
5
Q
Describe LANs
A
- high speed transmission over a restricted geographical area
- can be wired or wireless = schools/ unis
- if it’s too large, the signal can be boosted
- usually owned by a single person/ organisation
- e.g. connect LANs to PCs, tablets, printers at homes
6
Q
Describe WANs
A
- WANs are used to link LANs that are separated by large distances (few m to thousands of km)
- e.g. internet
- often collective or distributive ownership as more expensive to set up than LAN
- connected using telephone lines, satellite or radio links and organisations hire infrastructure to manage the WAN
7
Q
Describe PANs
A
- computer network organised around an individual so very short range
- mobile computers, phones or PDAs
- uses Bluetooth
- handy as no additional hardware = can create a PAN on the move
8
Q
What piece of hardware in a device allows it to connect to networks?
A
- NICs = Network Interface card (used for wired and wireless connections)
9
Q
What do switches do?
A
- connect devices on a LAN
10
Q
What do routers do?
A
- transmit data between diff networks and are normally used to connect to the network
- most routers in homes =a router, switch and WAP - all in one
11
Q
How can wired networks be connected?
A
- using diff cables
- choice of cable depends on cost, bandwidth and how far you want to transmit data
12
Q
What is bandwidth?
A
- amount of data that can be sent across a network at a given time
13
Q
What are the 3 diff cables for connecting networks?
A
- Fibre optic cables
- CAT 5c and CAT 6
- Coaxial cables
14
Q
In what circumstances are fibre optic cables used?
A
- can transmit data as light = high performance
- expensive
- don’t suffer inference
- can transmit over large distances at a high bandwidth without loss of quality
15
Q
In what circumstances are CAT 5c and CAT 6 used?
A
- common Ethernet cables
- contain pairs of copper wires which are twister to reduce internal interference
- cheaper than fibre optic
- decent bandwidth
- thus commonly used in houses for LANs networks
16
Q
In what circumstances are coaxial cables used?
A
- made of a single copper wire surrounded by plastic layer for insulation and metallic mesh for shielding from outside interference
- very cheap
- low bandwidth
17
Q
What are the 2 categories of networks?
A
- wired
- wireless
18
Q
What is the generic term for things such as wifi?
A
- WLANs
- Wireless Local Area Networks
19
Q
What do wireless networks use to transmit data?
A
- radio waves
20
Q
What is needed to set up a wireless network?
A
- wireless access point (WAP) device
- switch that allows devices to connect wirelessly
- WAP is not hotspots which are locations where you can connect to a WAP
21
Q
How can devices without wireless capability connect?
A
- use a dongle
- USB dongle = can be plugged into computers to allow them to connect wirelessly to the internet
- HDMI dongles = use wireless networks to streak high-quality video to a TV
22
Q
What are the benefits of wireless networks ?
A
- convenient as you can get it to connect automatically to the network and you can also move around while connected
- cheaper and better for the environment (don’t need wires)
- easy to add more users to a wireless network - don’t need to install extra wires or any complex setup
23
Q
What are the drawbacks of wireless networks?
A
- generally less secure than wired networks and access points are visible to all devices, not just trusted ones = allows hackers to gain access
- distance from WAP, interference from other wireless networks, physical obstructions can reduce signal strength - limit on how far they can reach
- lower bandwidth and less reliable
24
Q
Describe a star topology?
A
- all devices are connected to a central switch or server that controls the network
- central switch allows many devices to access the server simultaneously
- star networks may be wired or wireless
25
What are the pros of star topologies?
- if a device fails or a cable is disconnected, the rest of the network in unaffected
- simple to add more devices since each device is connected using a separate cable
- better performance than other setups and data goes straight to the central device so all devices can transmit data at the same time
- fewer data collisions compared to other network topologies
26
What are the cons of a star topology?
- wired networks = every device needs their own cable = expensive
- switch itself is also an expensive piece of hardware
- problem with the switch or server = whole network is affected
- maximum numbers of possible connections is determines by the switch = if you need more, need to buy a new one
27
What is bus topology like?
- connected to a single cable
- use a single ‘backbone’ cable, called a bus to connect all the devices
- 2 terminators are placed at the ends of the bus to stop data reflecting back along the bus
- without terminators, reflected signals would cause interference and potentially make network unstable
28
What are the pros of a bus topology?
- like star, the network is unaffected if a device fails
- aren’t dependent on central switch
- relatively cheap to set up compared to star network as total length of wiring is cheaper than switches, both to buy and maintain
29
What are the cons of bus topologies?
- data collisions are common on a bus network =data must be resent if collision = slows network down
- more devices you add to network = more likely collisions = unsuitable for larger networks
- to avoid collisions = devices must wait for the bus to be available before they can send any data = can also slow the network down
- if bus cable broken = splits network into separate parts without terminators at both ends = lots of reflected network = shuts down entire network
30
Define a network protocol
- a protocol is a set of rules for how devices communicate and how data is transmitted across the network
- covers how communication between 2 devices should start and end, how data should be organised and what to do if the data goes missing
- data is split into equally sized packets and each packet has extra information like the destination and source address and a checksum (used to find errors)
31
What is a layer?
- network protocols are divided into layers
- layer is a group of protocols which have similar functions
- layers are self contained - protocols in each layer do their job without needing to know what’s happening in the other layers
- each layer serves the layer above it
- data can only be passed between adjacent layers
32
How many layers are there in the TCP/IP model?
4 layers
- application
- transport
- internet
- link
33
Describe layer 1?
Layer 1 - Link layer
- passing data over the physical network
- responsible for how data is sent as electrical signals over cables, wireless and other hardware and interpreting signals using a device driver
34
What is an example of a protocol in the link layer?
WiFi or Ethernet
35
Describe layer 2?
- Layer 2 = internet layer
- adding IP addresses to data packets, directing them between devices and handling traffic
- used by routers
36
What is an example of a protocol in the internet layer?
IP
37
Describe layer 3?
- Layer 3 = Transport Layer
- setting up communications between 2 devices
- splitting data into packets and checking packets are correctly sent and delivered
38
What is an example of a protocol in the transport layer?
- TCP, UDP
39
Describe layer 4?
Layer 4 = application layer
- proving networking services to applications
- Turing data into websites
40
What is an example of a application in the link layer?
- HTTP
- FTP
- SMTP
41
What is the advantage of using layers?
- breaks network communication into manageable pieces - helps developers concentrate on only one area of the network
- layer area self - contained = they can be changed without the other layers being affected
- set rules for each layer forced companies to make compatible, universal hardware and software so different brands will work with each other and always work in the same way
42
What is the application responsible in the TCP/IP model?
- file, email and data transfer
43
What are the protocols in the application layer?
- HTTP - hyper text transfer protocol
- HTTPS - http secure
- FTP - file transfer protocol
- IMAP - internet message access protocol
- SMTP - simple mail transfer protocol
44
What is HTTP and HTTPS used for?
HTTP is used by web browsers to access websites and communicate with web servers
HTTPS is a more secure version of HTTP and encrypts all information sent and received
45
What is FTP used for?
- used to access, edit and move files between devices on a network
- e.g. to access files on a server from a client computer
46
What is IMAP used for?
- used to retrieve emails from a server
47
What is SMTP used for?
- used to send emails
| - also used to transfer emails between servers
48
What are TCP and UDP?
- transport layer protocols which control the packaging and unpackaging of data
- splits the data into packets
49
Describe TCP
- transmission layer protocol establishes a connection between sending and receiving devices
- splits data into numbered packets that can be reassembled into the original data once they reach destination, even if they arrive out of order
- communicates with the receiving device to make sure all packets have been transferred correctly - if not then missing or corrupted packets are resent
- sending device gets confirmation when the transfer is complete
50
Describe UDP
- user data gram protocol breaks data down into packets without numbering them
- read by the receiving device in the order they arrive - even if it’s not in they were sent
- UDP sends one packet at once and doesn’t check with the receiving device that everything has been received
- this saves time but there’s no way of knowing if packets have gone missing in transit
51
When is UDP more suitable?
- suitable for applications that need fast, efficient transmission (e.g. live video streaming)
- hiccup in video quality from missing packet is better than a delay in the life stream
52
When is TCP more suitable?
- better when you need a reliable connection (e.g. downloading files)
- missing data packets can cause files to be corrupted and unusable but you wouldn’t want to have to redownload the whole file
53
What is an IP responsible for?
- packet switching
| - internet protocol = IP
54
What layer does IP operate on?
- Internet layers
- establishes connections between routers and handles network traffic - IP addresses are unique numbers assigned to every device connected to an IP network - added to the header of each packet at the internet layer
55
What is the IP responsible for?
- directing data packets to their destination across the internet or other IP networks using packet switching
- each packets is sent between a series of routers within reads each ones header and decides which router to send the packet to next
- way the data sent changes depending on network traffic - packets can take diff routes and routers may prioritise packets
56
Why is packet switching efficient?
- so many possible routes that each packet can take
| - so packets receive device quickly even if there’s heavy traffic
57
What is WIFI the standard protocol for?
- wireless LANS
58
At which layer does WiFi operate?
- link layer
- units of data sent in the link layer are called frames, not packets
- uses MAC address for frames to devices
59
What bands does WiFi use and when is each band better?
- uses 2 radio Hz bands
- 2.4 GHz and 5GHz
- 2.4 GHz has a greater range and is better at getting through walls and other obstructions while 5GHz is better over short distances
60
What are the Hz bands split into?
- split into numbered channels that each cover a small Hz range
- some channels in the 2.4 GHz band overlap
- networks using adjacent or overlapping channels can cause interference
61
What security protocols encrypt data in WiFi?
- WPA (WiFi protected access)
| - WPA2
62
What is Ethernet?
- family of protocols that operates on the link layer
| - handles the transmission of data between 2 devices on LANs but Ethernet is specifically used for wired connections
63
What is a node?
A device in a network topology
64
How can networks be protected against threats?
- encryption
- anti-malware software
- user access levels
- automatic software updates
- MAC address filtering
65
How can networks be protected with encryption?
- when data is translated into a code when only someone with the correct key can access
- cipher text into plain text
- needed to send data over network securely
66
How can networks be protected with anti-malware software?
- stops malware from damaging the network
- e.g. firewall examines all data and blocks potential threats
- prevents unauthorised access into the network
67
How can networks be protected with user access levels?
- some have higher access levels than others and access to more sensitive data
- limits the number of people with access to important data so prevents attacks within an organisation
68
How can networks be protected with automatic software updates?
- used to fix security holes
| - unpatched software can be easily exploited
69
How can networks be protected with MAC address filtering?
- way of making sure only people on a network are trusted users
- checks unique identification so only allowed devices can join the network
