3.5 Fundamentals Of Computer Networks Flashcards
1
Q
Computer network definition:
A
Devices connected together that allow these devices to share information and resources
2
Q
Benefits of compute networks:
A
- sharing files is easier (network users can access files, work on them at same time, copy files between machines)
- can share the same hardware (printers) between multiple devices
- can install/update software on all computers at once (not one-by-one)
- can communicate across a network cheaply & easily (email)
- user accounts can be stored centrally (users can log in from any device on the network)
3
Q
Risks of computer networks:
A
- can be expensive to set up (often need lots of extra hardware)
- can be vulnerable to hacking
- malware can easily spread between networked computers
- some dependent on 1+ servers, if servers go down it can be disruptive for people using network
- large networks difficult to manage, may require employing a specialist to maintain them
4
Q
Main types of computer network:
A
- Personal Area Network (PAN)
- Local Area Network (LAN)
- Wide Area Network (WAN)
5
Q
Personal Area Network (PAN)
A
= connects devices in a very short range
- normally centred around a single user
- often used to transmit between mobile/wearable devices
- use common wireless tech (Bluetooth) to connect devices
Bluetooth = strong but short range so ideal for connecting devices in same room
- handy as don’t require additional hardware (can create on the move)
6
Q
Local Area Network (LAN)
A
= covers a small geographical area located on a single site
- all hardware owned by organisation that uses it
- can be wired (ethernet cables) or wireless (wi-fi)
- often in businesses, schools, universities
- many homes have it to connect various devices (PCs, tablets, printers, smart TV)
7
Q
Wide Area Network (WAN)
A
= connects LANs in different geographical locations
- organisations hire infrastructure from telecommunication companies, who own and manage WAN (as very expensive to set up)
- so under collective/distributed ownership
- may be connected using telephone lines (copper/fibre optic), satellite links, or radio links
- internet = one big WAN
8
Q
Switch:
A
Connects devices on a LAN
8
Q
Router:
A
Transmits data between different networks different networks (mostly to connect to internet)
9
Q
What is a Network Interface Card (NIC)
A
= piece of hardware inside a device, allows it to connect to networks
(For both wired and wireless connections)
10
Q
What are local wireless networks called?
A
= WLANs (wireless LANs)
Wi-Fi = specific family of WLAN protocols
11
Q
What is a WAP?
A
WAP = wireless access point device
Needed to set up wireless network, allows devices to connect
13
Q
What do wireless networks use to transmit data?
A
Radio waves
13
Q
Benefits of wireless networks (compared to wired networks):
A
- convenient, device can automatically connect to network & move around while connected
- can be cheaper & better for environment (don’t need wires)
- very easy to add more users (don’t need to install extra wired/do a complex setup)
14
Q
Risks of wireless networks (compared to wired networks):
A
- generally less secure, access points usually visible to all devices (not just trusted ones) = can allow hackers to gain access
- distance from WAP, interference from other wireless networks, physical obstructions = reduce signal strength, limit to how far network can reach
- lower bandwidth & less reliable
15
Q
List different cables used to connect devices on a wired network:
A
- fibre optic cable
- CAT 6/5e, twisted copper cable
- coaxial cable
16
Q
Twisted pair of copper wires (CAT 6/5e) cable:
A
- common type of Ethernet cable
- pair of copper wires twisted together to reduce internal interference
- cheaper
- decent bandwidth (used for LANs)
18
Q
Coaxial cable
A
- single copper wire surrounded by plastic layer for insulation & metallic mesh to provide shielding from outside interference
- very cheap
- low bandwidth
19
Q
Fibre optic cable:
A
- transmits data as light
- high performance & expensive
- don’t have interference
- can transmit over very large distances at high bandwidth without loss of signal quality
20
Q
network topology definition:
A
The layout of a network
21
Q
List the common network topologies:
A
- star topology
- bus topology
22
Q
Star topology:
A
= all devices are connected to a central switch or server that controls the network
- central switch allows many devices to access server simultaneously
- may be wired/wireless
23
Q
Pros of star topology:
A
- if device fails/cable disconnects, rest of network is unaffected
- simple to add more devices (each device connected to switch using separate cable)
- better performance, data goes straight to central device so all devices transmit data at same time
- fewer data collisions
24
Q
Cons of star topology:
A
- in wired networks, every device needs cable to connect to central server/switch = expensive
- central switch = expensive piece of hardware
- is problem with switch/server, whole network affected
- max no. of possible connections determined by switch, if more is needed, need to buy a new one
25
Bus topology:
= use a single ‘backbone’ cable (bus) to connect to all devices
= 2 terminators places at ends of bus to stop data reflecting back along bus (reflected signals cause interference & potentially make network unusable)
- only wired networks
26
Pros of bus topology:
- network unaffected if device fails
- aren’t dependant on a central switch working to keep network running
- relatively cheap to set up, less wiring needed
- hardware needed (bus cable,terminations) cheaper to buy & maintain than switches
27
Cons of bus topology:
- data collisions common, then data must be reset which slows network down
- more devices added = more likely data collisions so unsuitable for large networks
- devices must wait for bus to be available to send any data to avoid data collisions = slows network down
- if bus cable breaks, splits network into separate parts which don’t have terminators at each end = lots of reflected signals, can shut down entire network
28
Network protocol definition
A set of rules for how devices communicate and how data is transmitted across a network
- how communication between 2 devices should start/end
- how data should be organised
- what devices should do if data goes missing
29
List common network protocols:
- Ethernet
- Wi-Fi
- TCP (Transmission control protocol)
- UDP (User data gram protocol)
- IP (Internet protocol)
- HTTP (Hypertext Transfer Protocol)
- HTTPS (Hypertext Transfer Protocol Secure)
- FTP (File Transfer Protocol)
- email protocols:
- SMTP (Simple Mail Transfer Protocol)
- IMAP (Internet Message Access Protocol)
30
Purpose & use of Ethernet:
= family of protocols that operates on the link layer
- handles transmission of data between devices on LANs
- for wired connections
31
Purpose & use of Wi-Fi:
= standard family of protocols for WLANs (link layer)
32
TCP (Transmission Control Protocol)
= establishes connection between sending & receiving devices
- then splits data into numbered packets (can be reassembled at destination)
- communicates with receiving device to check all packets have been transferred correctly
- sending device gets confirmation when transfer complete
33
UDP (User Datagram Protocol)
= breaks down data into packets without numbering them
- unnumbered packets read by receiving device in order they arrive (may not be order sent)
- only sends each packet once, doesn’t check if they have been received
= saves time, don’t know if packets have gone missing in transit
34
IP (internet protocol)
= establishes connections between routers & handing network traffic
- IP address = unique number assigned to every device connected to IP network
- directs data packets to destination using packet switching, each packet sent through series of routers which read packet’s IP address to decide which router to send packet to next
- packet switching = efficient as many possible routes packet can take, packets reach receiving device quickly, even if traffic
35
HTTP (Hyper Text Transfer Protocol)
= used by web browsers to access websites & communicate with web servers
36
HTTPS (Hyper Text Transfer Protocol Secure)
= more secure version of HTTP, encrypts all info sent & received
37
FTP (File Transfer Protocol)
= used to access, edit, move files between devices on a network
38
IMAP (Internet Message Access Protocol)
= used to retrieve emails from a server
39
SMTP (Simple Mail Transfer Protocol)
= Used to send emails & transfer mails between servers
40
Need for network security?
They are vulnerable to attacks by criminals
| Protects against damage, cyber attacks & unauthorised access
41
Methods of network security:
- authentication
- encryption
- firewall
- MAC address filtering
42
Authentication
= makes sure anyone trying to access network is who they say they are, prevents unauthorised people for accessing data from network
- passwords
- biometrics
- email confirmation
- CAPTCHA
43
Encryption
= when data is translated into code which only someone with correct key can access (unauthorised users can’t read it), essential for sending data over a network securely
- encrypted text = cipher text
- non-encrypted text = plain text
44
Firewall
= anti-malware software which examines all data entering & leaving a network & blocks any potential threats
- used to prevent unauthorised access to a companies network
45
MAC address filtering
= checks unique identification (MAC address) of each device that tries to connect to network & only lets allowed devices to join network, blocks others
makes sure only people on a network are trusted users
46
User access levels (authentication)
= control which parts of network different groups of users can access
- limits no. of people with access to important data, help to prevent attacks from within an organisation
47
4 layer TCP/IP model: (protocols operating on that layer)
- application layer(4) = HTTP, HTTPS, FTP, SMTP, IMAP
- transport layer(3) = TCP, UDP
- internet layer(2) = IP
- link layer(1) = Wi-Fi, Ethernet
48
Application layer
= provides networking services to applications
| = where network applications (web browser, email programs) operate
49
Transport layer
= sets up communications between 2 devices(hosts), splits data into packets & checks packets correctly sent/delivered
= hosts agree settings (language, size of packets)
50
Internet layer
= adds IP addresses to data packets, directs packets between devices & handles traffic, used by routers
= routes packets across network
51
Link layer
= passes data over physical network, responsible for how data is sent as electrical signals over cables, wireless & other hardware, interprets signals using device drivers
- where network hardware (NIC - Network Interface Card) & device drivers sit
