1.3 - Computer networks, connections and protocols Flashcards
What does LAN stand for?
Local Area Network
What is a LAN?
- Covers a small geographical area
- All hardware is owned by the organisation that uses it
- Either wired or wireless
Where would you often find LANs?
- Businesses
- Schools / Universities
- Homes (connects PCs, TVs, Printers etc)
What are some advantages of using a LAN?
- Sharing files is easier
- You can share the same hardware
- Internet connection can be shared between every device that is connected
- You can install/update software simultaneously rather than one-by-one
- User accounts can be stored centrally
- You can communicate w/ LAN users cheaply & easily
What does WAN stand for?
Wide Area Network
What is a WAN?
- Connects LANs that are in different geographical locations
—> A network that is spread over a large geographical area - They use third party infrastructure
How are WANs connected?
May be connected using fibre or copper telephone lines, satellite links or radio links
Give an example of a WAN:
The internet
What are the types of Network connection devices?
- Hubs
- Switches
- Wireless access points
- Routers
What is an NIC?
Where is it found?
- Internal piece of hardware
- Allows a device to connect to a network
- Used to be on separate cards but now built into the motherboard
What is the purpose of a Switch?
Connects devices on a LAN
They receive data from one device & transmit this data to the device on the network (with the correct MAC address)
In what units do Switches receive data?
Frames
What is Routers responsible for?
Transmitting data between networks
Where are Routers used & why?
In homes & offices to connect the LAN to the internet
What is the role of Routers on the internet?
Directing data (packets) to their destination
What are the most common Ethernet cables & what are they?
CAT 5e & CAT 6
‘Twisted pair’ cables, contains 4 pairs of copper wires which are twisted together
What is the purpose of the ‘4 pairs of copper wires which are twisted together’ in an Ethernet cable?
To reduce internal interference
What are coaxial cables made of?
A single copper wire surrounded by a plastic layer and a metallic mesh
What is the purpose of the plastic layer in a Coaxial cable?
Insulation
What is the purpose of the metallic mesh in a Coaxial cable?
Provides shielding from the outside interference
What is the purpose of a Fibre Optic Cable?
To transmit data as light
What are the advantages of a Fibre Optic Cable?
- Greater BANDWIDTH = transfer speeds are faster
- Can transmit over VERY LARGE DISTANCES without LOSS OF QUALITY
What are the disadvantages of a Fibre Optic Cable?
- Very Expensive
What is Radio waves used for in a wireless network?
To transmit data
Name 2 common wireless technologies:
- Wi-Fi
- Bluetooth
How are wireless networks more convenient than wired networks?
- As you can move around while still being connected
- Cheaper - needs fewer wires
Describe what is Bluetooth?
- Direct connection between 2 devices so data can be shared
- Low bandwidth compared to Wi-Fi
What is the typical connection range for Bluetooth?
Connection range varies but its usually 10 metres
Where is Bluetooth often used?
Often used in mobile/ wearable devices (headphones, smartwatches etc)
Describe what is Wi-Fi?
- Can connect multiple devices to a LAN at the same time
- High bandwidth compared to Bluetooth
What is the typical connection range for Wi-Fi?
40 - 100 metres
Where is Wi-Fi often used?
Homes (Routers, Desktops, Laptops etc)
What does a WAP stand for?
Wireless access point
What is a WAP?
A device that connects computers to a network using Wi-Fi.
Similar to a switch
What do devices need to connect to a WIFI?
A wireless NIC
Often built into the device
What can you use if you don’t have a NIC?
A dongle
What are the types of Dongles?
- USB dongles
- HDMI dongles
What is the purpose of a USB dongle?
Can be plugged into computers to allow them to connect wirelessly to the internet
What is the purpose of a HDMI dongle?
Can use wireless networks to stream high-quality video to a TV
What factors affect network performance?
- Number of devices on the network
- The bandwidth of the
transmission medium - Type of network traffic
- Network latency
- The number of transmission errors
- Network topology
What is Bandwidth?
Measures the amount of data that can transfer through a communications channel over a given period of time
What happens to a network if the bandwidth is high?
The network can preform better
What is available bandwidth shared between on a network?
The devices on a network
What happens to a network when there are too many devices or heavy use of it?
May cause congestion & slow the network
How can you fix network congestion/ heavy use?
Limit the bandwidth available to individual users
Wired or wireless?
What type of connection is faster & more reliable?
Wired
What type of cable gives better performance?
Fibre optic
Rather than copper
What does wireless performance depend on?
Signal quality
What is wireless performance affected by?
- Range of the device
- Amount of interference from other wireless networks
- Physical obstructions (e.g. Thick walls from buildings)
What manages the client-server network?
A server
What are the devices that are connected to the server called?
In a client-server network
Clients
What type of organisations would be best suited for client-server networks?
- Organisations with many computers
- Situations where many computers need access to the same information
Give an example of a type of organisation that would use client-server networks:
Schools
What is a server?
A computer that manages and stores files
What are the advantages of client-server networks?
- Easy to keep track of files
- Easier to preform backups
- Easy to install & update software
- Easy to manage network security
- Reliable & always on
Why is it ‘easy to keep track of files’ in a client-server networks?
They are stored centrally
What are the disadvantages of client-server networks?
- Expensive to set up
- Needs IT specialists to maintain network & server
- Server dependence
- May become overloaded if too many people are accessing it at once
Why is ‘Server dependence’ a risk in a client-server network?
If the server goes down all clients lose access to their work
What are the advantages of peer-to-peer networks?
- Easy to maintain
- No dependence on server
Why are peer-to-peer networks easy to maintain?
As you don’t need any expertise or expensive hardware
Why is server dependence in a peer-to-peer networks an advantage?
If one device fails the whole network isn’t lost
What are the disadvantages of peer-to-peer networks?
- No centralised management
- Machines are prone to slow down when other devices access them
- Less reliable: data may be lost if one fails
- Copying files between devices creates duplicate files
Why is no centralised management in a peer-to-peer networks a disadvantage?
- Devices need updates and security installed individually
- Backups are more complicated
Where might you use a peer-to-peer network?
At home to share files between devices or connect devices to a printer
Name some server types
- File server
- Web server
- Print server
- Applications server
- Mail server
What is a file server?
Hold and maintain user files
What is a web server?
Hold and share web pages
What is a print server?
Manage printing across a network
What is a mail server?
Handle emails between users
What is a applications server?
Allows programs to be run over a network
What is a star topology?
A network where each node is connected to a central switch
What are some advantages of the star topology?
- If a device fails / cable is disconnected - rest of network unaffected
- Simple to add more devices to the network
- Better performance than other setups
What are some disadvantages of the star topology?
- Expensive = every device needs a cable to connect to the central switch or server
- If there is a problem w/ the switch - whole network is affected
How does the star topology have better performance than other setups?
Data flows in one direction (unlike bus network) & all devices can transmit data @ once (unlike ring network)
What is a bus network?
All devices are arranged in a line, connected to a single backbone cable
What is a disadvantage of the bus network?
Devices send data in both directions = causes data collisions
What is a ring network?
Data moves in one direction around the ring, preventing data collisions
What is a disadvantage of the ring network?
One device can send data at a time & data passes through many devices before its destination
What is a mesh topology?
All devices are connected to each other
How do mesh networks work?
By sending data along the fastest route from one device to another
What are some advantages of the mesh topology?
No single point where the network can fail
Explain how there is No single point where the network can fail in a mesh topology?
If one device fails, then the data is sent along a different route to get to its target
What are some disadvantages of the mesh topology?
Very expensive = needs a lot of wires to connect devices together
What’s the difference between a full mesh and a partial mesh topology?
Full mesh = Every device is connected to every other device
Partial mesh = Not all devices are fully connected
What does HTTP stand for?
Hyper text transfer protocol
What is HTTP used for?
Used by web browsers to access websites and communicate with web servers
What does HTTPS stand for?
Hyper text transfer protocol - secure
What is HTTPS used for?
- More secure version of HTTP
- Encrypts all information send and received
What does FTP stand for?
File transfer protocol
What is FTP used for?
Used to access, edit & move files between devices on a network
What does POP3 stand for?
Post office protocol (version 3)
What is POP3 used for?
Used to retrieve emails from a server
—> Holds email until YOU download it (then it is deleted)
What does IMAP stand for?
Internet message access protocol
What is IMAP used for?
Used to retrieve emails from a server
—> Holds emails until YOU delete it (you only download a copy)
Which protocol is used by most web-based email clients?
IMAP
What does SMTP stand for?
Simple mail transfer protocol
What is SMTP used for?
- Used to send emails
- Also used to transfer emails between servers
What does TCP stand for?
Transmission control protocol
What’s TCP used for?
- Sets the rules for how devices connect on a network
- Splits data into packets & reassembles at the destination
- Checks data is correctly sent & delivered
What does IP stand for?
Internet protocol
What’s IP used for?
Directing packets to their destination across a network
What is a layer?
A group of protocols which have similar functions
A division of network functionality
Give some characteristics of layers
- Self-contained
- Each layer serves the layer above it
- Data can only be passed through adjacent layers
What are the advantages of layers?
- Breaks network communication into manageable pieces
- Self contained
- There are standards for each layer
How is having standards for layers an advantage?
Forces companies to make compatible, universal hard/software - different brand will work w/ each other
How is breaks network communications into manageable pieces an advantage for layers ?
Helps developers to concentrate only on 1 area without having to worry about the others
How is layer’s being self contained an advantage?
They can be changed without the other layers being affected
What is Hosting?
When a business uses servers to store files of another organisation
What is cloud computing?
When clients access data storage, software & processing power remotely over the internet
What are the advantages of the cloud?
- Users can access files & applications from any connected device
- Easy to increase how much storage is available
- Automatic updates
- No need to but expensive hardware
What are the disadvantages of the cloud?
- Needs connection to the internet
- Dependant on the host for security & backups
- Subscription fees for using cloud storage & software can be expensive
- Data can be vulnerable to hackers
What are URLs?
Addresses used to access web servers & resources on them
What is a DNS used for?
To translate website domain names into IP addresses
What does a DNS server store?
A list of domain names & a list of corresponding IP addresses where the website is stored
Describe the steps taken to display a webpage
1) Domain name is typed into the address bar of the browser
2) A query is sent to the local DNS server for the corresponding IP address if that domain name
3) Local DNS server will check if it holds that info. If it does, it’ll pass the IP address to the browser
4) Browser connects to the IP address of the server & accesses the website
What will happen if the local DNS server does not hold the IP address?
The query is passed to another DNS server at a higher level until the IP address is resolved
What is the internet?
A global network of interconnected networks
What is the purpose of a web server?
Processes the client request to prepare the webpage & return it so the web browser can display it to the user
What is a domain registrar?
A company that checks the domain name is valid and not already taken
What are networking standards?
Rules that allow computer systems to communicate across networks
Why have networking standards been created?
To ensure devices can exchange data & work together
What is the TCP/IP model used for?
To visualise the different parts of a network as each layer has specific roles
How many layers are there in the TCP/IP model?
4
Why is splitting a network design into layers beneficial?
As it simplifies design - making it easier to modify & use
What is the purpose of the data link layer?
Handles the transmission errors & passes data to the physical layer
What layer number is the data link layer?
1
Which protocols are in the data link layer?
Ethernet
What is the purpose of the internet layer?
Finds the optimal route for the data to take is calculated
What layer number is the internet layer?
2
Which protocols are in the internet layer?
IP
What is the purpose of the transport layer?
Makes sure the data is sent & received in the correct order & reassembled at the destination without errors
What layer number is the transport layer?
3
Which protocols are in the transport layer?
TCP
What is the purpose of the application layer?
Allows humans & software applications to use the network
What layer number is the application layer?
4
Which protocols are in the application layer?
- HTTP
- HTTPs
- SMTP
- FTP
