Networks (Ch13) (M1) Flashcards
1
Q
What must all devices have, to join a network?
A
A Network Interface Card (NIC)
2
Q
What address does each NIC have?
A
Each NIC has a Media Access Control (MAC) address
3
Q
What do MAC addresses do?
A
MAC addresses are used to route frames around a LAN
4
Q
What are frames?
A
Frames are units of data
5
Q
What is a MAC address?
A
A MAC address is a unique identifier to allow a device to be found on a network
6
Q
Describe the format of a MAC address
A
A MAC address has 6 groups of hexadecimal numbers, usually separated by colons, or dashes.
They are 48 or 64-bit binary numbers, converted to hexadecimal for ease.
7
Q
What are IP addresses used for?
A
IP addresses are used to route packets around a WAN
8
Q
When sending data between TCP/IP networks over the internet, what is used?
A
IP addresses are used
9
Q
What are MAC addresses linked to?
A
MAC addresses are linked to the hardware
10
Q
What are the two ways that an IP address can be assigned?
A
IP addresses are assigned either manually (static) or automatically (dynamic)
10
Q
Which address is not linked to the hardware?
A
IP addresses aren’t linked to hardware
11
Q
What does the IP address enable every device to be?
A
The IP address enables every device on the network to be identified and located
12
Q
What is a static IP address? What do they do, and why are they used?
A
A static IP address is permanent. They connect printers on a LAN, and are used fort hosting websites on the Internet - because companies don’t want the IP address of their website changing.
13
Q
What is the disadvantage of static IP addresses?
A
Static IP addresses can be very expensive
14
Q
What is a dynamic IP address? What do they do, and why are they used?
A
A dynamic IP address is temporary and changes each time the device accesses the internet.ISPs commonly use dynamic IP addresses because they’re more cost effective, and can be reused.
15
Q
What are the advantages of dynamic IP addresses?
A
Dynamic IP addresses are cost effective and can be reused
16
Q
What does every URL have?
A
Every URL has an IP address that it relates to
17
Q
What does every IP address have?
A
Every IP address has a network and host address
18
Q
Describe the format of an IPv4 address
A
An IPv4 address is made up of a set of four numbers. Each of the four numbers is separated by a dot.
For example: 76.215.67.190
19
Q
Describe the format of an IPv6 address
A
An IPv6 address is written as eight groups, separated by colons. Each group made up of four hex values representing 16-bits.
For example: 49cd:c92d:dabb:469f:003c:4877:f44b:5441
20
Q
Describe the differences in format between IPv4 and IPv6 addresses
A
IPv6 is written as eight groups, instead of four groups like IPv4.
Additionally, an IPv6 address is made up of four hex values, representing 16-bits, but an IPv4 address is made up of four parts with eight bits each
21
Q
What is the main advantage of IPv6 addresses?
A
An IPv6 format allows for many trillions of combinations, instead of the around 4 billion combinations that IPv4 offers
22
Q
Describe the limitations of the IPv4 format
A
Being limited to 4 billion IP addresses was a big problem as even a few decades ago, we were already exceeding this in the number of internet-enabled devices
Unique static addresses are running out
23
Q
Describe the trend in the number of devices being connected to the internet
A
The number of devices connecting to the internet is growing at an exponential rate
24
How many devices were estimated to be connected to the internet, in 2020?
There was an estimated 50 billion devices connected to the internet in 2020
25
How many possible addresses are there, using IPv4?
The IPv4 format has around 4 billion possible addresses
26
How many possible addresses are there, using IPv6?
The IPv6 format has 340 undecillion (3.4 x 10^38) possible addresses
27
What does encryption prevent unauthorised users from doing? How does it do this?
It prevents unauthorised users from obtaining readable data
This is done by scrambling the data into cipher text using a "master key", which is created from the SSID of the network and the password
28
Give two protocols used for wireless encryption
Protocols used for wireless encryption: WEP, WPA, WPA2
29
During wireless decryption, data is decrypted using the same what?
Data is decrypted using the same master key
30
What do protocols help to exchange, prior to transmission during wireless decryption?
Protocols help to exchange the master key, prior to transmission
This includes WEP, WPA, WPA2, and WPA3
31
What does each wireless network have?
Each wireless network has a SSID (Service Set Identifier)
32
What can the SSID be protected using?
The SSID can be protected with a password
33
Describe how an SSID can be protected
The SSID can be protected with a password
Data can then be encrypted by scrambling the data into cipher text
A master key created from the SSID and password enables this
34
What is the internet?
The internet is a global system of computer networks
It is the hardware needed to access the World Wide Web
35
Describe how a user can connect to the internet
How a user can connect to the internet:
- Home network has a wireless router
- Wireless router connects to an Internet Service Provider (ISP) via fibre optic
- ISP connects to Domain Name Server (DNS) and other routers on the Internet
- Those routers are connected to other LANS, routers and servers
36
Describe how a user can view a webpage
How a user can view a webpage:
- You type the website’s URL into your web browser
- Your web browser sends a request to a DNS server
- The database on the DNS server is checked and the website’s IP address is located
- The IP address is sent back over the internet, to the web browser on your computer
- Your web browser uses the IP address to find the physical location of the server hosting the website
- Your web browser sends a request to the server hosting the website to send the web page you want to view
- The server hosting the website splits the page into data packets and sends back to your web browser
- Your web browser reassembles the web page and displays it to you as a complete page
37
Give three examples of cloud services, and one application that fits into each category
Examples of cloud services:
Streaming services, e.g. Netflix, Spotify
Online applications, e.g. Google Docs, Office 365
Online storage, e.g. Dropbox, Amazon web service
38
Give three advantages of the cloud
Advantages of the Cloud:
- You can access data from any device with an internet connection
- It is easy to share files with other users
- Multiple people can work on the same file simultaneously
- The cloud host provides security and backups
- There is no need to buy expensive hardware to store data or run complex applications
39
Give two disadvantages of the cloud
Disadvantages of the Cloud:
- If you don't have an internet connection, you can't log in and access your files
- If you forget your login details, you can't access any of your files and media
- There is a risk of hackers being able to access your private data and files
- Some cloud services charge an ongoing monthly or annual fee
40
Describe the process of hosting
Hosting:
1. Web addresses which are easier for humans to remember are converted to IP addresses for routers by a Domain Name Service (DNS) resolver server.
2. This actual process is carried out by the Domain Name Service which is in reality multiple domain name servers.
3. Websites are stored on servers dedicated for this purpose.
41
Give two things that hosted applications provide
Hosted applications provide:
24/7 access
Multiple users
Greater security
42
What is cloud storage?
Cloud storage is the servers that store data and programs remotely that can be accessed and used over the Internet
43
Clients request or use services from what?
Clients request or use services from a server
44
What does ISP stand for?
ISP stands for 'Internet Service Provider'
45
What is an ISP?
An ISP is a company that provides you with access to the internet
46
ISPs normally charge a monthly fee for their service. What happens if you don't pay this, or cancel your contract?
If you don’t pay the fee, or you cancel your contract, you won’t be able to use the internet (except in public Wi-Fi hotspots)
47
Give two examples of ISPs
Examples of ISPs:
Virgin, BT, Sky, EE
48
What does URL stand for?
URL stands for 'Uniform Resource Locator'
49
There are billions of web pages on the internet. How do we identify them all?
Each web page is assigned a URL
50
Each website has a unique what?
Each website has a unique address - A URL
51
What does DNS stand for?
DNS stands for 'Domain Name System'
52
What does the DNS act as?
The DNS acts as a directory of every domain name (for example, [www.bbc.co.uk](http://www.bbc.co.uk/)) and its corresponding IP address (151.101.128.81)
53
Because of the DNS, what do you not need to know for each website?
Because of the DNS, you do not need to know every IP address for each website you want to visit
54
What does the DNS translate?
The DNS translates human-readable domain names to the numeric IP address that the computer uses
55
What is hosting?
Hosting is where a website is stored on a web server
56
Give three things on the internet that are stored on web servers
Data and programs stored on web servers:
Document and file storage
Video streaming
Gaming
Instant messaging
Email services
Peer-to-peer file sharing
57
What are the two types of hosting?
The two types of hosting are local hosting and external hosting
58
What is local hosting?
Local hosting is where you host a website on your own computer
59
If you plan to host a website locally, you need to set up your computer as a web server. Why?
Setting your computer as a web server will enable people to connect to your computer to access the website and any related files
60
Give three advantages of local hosting
Advantages:
- Speed – hosting your website locally on your computer means that it will run much faster than if it were hosted on a server in a different country
- It is less expensive than external hosting as there is no rental charge
- It gives you full control of your website
- Privacy – you may want a website for your own use
61
Give three disadvantages of local hosting
Disadvantages:
- You need technical knowledge to host a website locally
- Your computer always needs to be switched on, otherwise the site will be unavailable
- Bandwidth can be an issue – especially if your website is popular
- You are responsible for the backups
62
Which hosting method do most people choose?
Most people choose to host their website externally
63
What is external hosting?
External hosting is where you pay a web hosting company a monthly fee to host your website on one of their servers
64
Give two advantages of external hosting
Advantages:
- Additional bandwidth is available at a cost
- The hosting company will maintain the server and ensure that it is always available
- The hosting company will perform regular backups, virus, and malware scans
65
Give two disadvantages of external hosting
Disadvantages:
- Cost – external hosting can be expensive
- Potential downtime – if the company's server goes offline, your website will be unavailable
- Updates – if the company upgrades their software, it might mean that some of the code used on your website is incompatible. This can cause parts of your website to 'break'.
66
Why are wireless networks more convenient than wired networks?
Wireless networks are more convenient than wired networks because you can move around while still being connected - they are also cheaper because you need fewer wires
67
What is Ethernet?
Ethernet is a group of protocols responsible for sending and receiving data along a cable
68
What protocol is most common for putting together a LAN?
Ethernet is the most common protocol used for putting together a local area network (LAN)
69
What are the three parts of the Ethernet protocol?
The Ethernet protocol has several parts:
Hardware - specifies the performance of network cables, plugs, and sockets
Data format - describes the format of the data packets to be sent or received
How to deal with data collisions
70
Give three advantages of Ethernet
Advantages of Ethernet:
- It doesn't require any switches or hubs
- Maintenance and administration are simple
- Relatively inexpensive to set up an ethernet connection
- Very high speeds - higher than Wi-Fi
71
Give three disadvantages of Ethernet
Disadvantages of Ethernet:
- If there is any problem, it's difficult to troubleshoot what cable or node within the network is causing a problem
- Not suitable for traffic-intensive applications. If the rate of traffic goes up, efficiency of ethernet goes down.
-Cost - more cables are needed to add a new device
-Safety - cables can be trip hazards, so routing is needed along walls and under floors
72
What is Wi-Fi?
Wi-Fi is a set of protocols that define how network devices can communicate wirelessly, over radio waves
73
Give four advantages of Wi-Fi
Advantages of Wi-Fi:
- Portability - devices can be used in a greater number of places and settings
- Number of devices supported - more devices can be connected to a network, flexibility to add new devices without needing additional hardware
- No cables - no installation of cables is needed, this takes less time and saves money
- Users can move freely and share data and files with others.
- It is convenient for business
- Allows for an instant transfer of data, for example on social media
74
Give three disadvantages of Wi-Fi
Disadvantages of Wi-Fi:
- Speed - Wi-Fi tends to be slower than wired networks
- Signal strength - Wi-Fi is reliant on a signal from the WAP which could suffer from interference
- Security - less secure than a wired network and more vulnerable to attack
75
What are Wi-Fi, Bluetooth, and Ethernet all examples of?
They are all protocols
76
What range is Bluetooth designed to work up to?
Bluetooth is designed to work up to 10 metres
77
Bluetooth requires two devices to be close to each other. Why?
To send and receive data between devices, because it has a short range of 10 metres
78
What kind of connection is Bluetooth usually?
Bluetooth is usually a direct connection between two devices so that data can be shared
79
What is Bluetooth often used in?
Bluetooth is often used in mobile or wearable devices - such as smartphones, watches, headphones, etc
80
Give three advantages of Bluetooth
Advantages of Bluetooth:
- It has a low power consumption
- It is very compatible, so is ideal for personal and mobile devices
- Has a low cost to set up
81
Give three disadvantages of Bluetooth
Disadvantages of Bluetooth:
- It has a very short range - 10m
- It has a very slow transfer speed
- Data can be intercepted by anyone within range, giving it weak security
82
Why might a gamer use:
-A wireless controller
-Wireless headphones
-A wired ethernet connection to their console
A gamer might use:
- A wireless controller - for convenience and portability
- Wireless headphones - for convenience and portability
- A wired ethernet connection to the console - for speed and reliability
83
Describe technology that a café owner may use, to help them run their business
A café owner might:
- Have a work laptop or computer with a wired ethernet connection - for better security and reliability
- Have a WAP for customers to use mobile devices, laptops via Wi-Fi - able to extend to provide lots of new connections
- Having free Wi-Fi could help attract customers
84
Describe technology that a businessman may use, to help them run their business
A businessman might:
- Use a wireless connection for a laptop, mobile, or tablet device - this is convenience when travelling, hotdesking, visiting other locations and companies
- Use a wireless Bluetooth connection to connect his phone to his car - to take calls if any of his employees wants to contact him
- Use a wired ethernet connection if he is based in an office with a laptop or PC - this is for security, speed, and reliability
85
In computer science, what is an architecture?
An architecture is the layout of a network
86
What are the two examples of network architecture?
The two examples of network architecture are: Client-server network, peer-to-peer network
87
What is a client-server network managed by?
A client-server network is managed by a server
88
What are devices that connect to a server called?
Devices that connect to the server are clients
89
What is a server?
A server is a powerful, specialist computer which is designed to allow multiple users to access it
90
In a client-server network, what is the main job of the server?
The server's primary role is to store and 'serve' files and resources to users, whenever they are requested by the clients. This is the client-server relationship.
91
Give three things a server can manage
Servers can manage:
Printing jobs
Access to the internet
Email services
Data backups
Store and serving files to users
92
Describe how a user logs onto a client server network
1. To use the network, the person must log on with a username and password.
2. The server checks that the username exists and that the password correctly matches it. This is authentication.
3. Once a user has logged onto the network, they can request files and resources stored on the server.
4. They can also send work to print, access their email, and the internet.
93
On a client-server network, why can users log onto any computer and still access their files?
Because resources are stored on the file server, rather than individual workstations, users can log onto any computer on the network and still access their files.
94
On a client-server network, where are backups made from?
Backups can be made centrally from the file server
95
On a client-server network, where can software updates be installed from? Why is this an advantage?
Software updates can also be installed from the central server, which saves time and ensures that nothing is missed
96
Where are peer-to-peer networks usually found?
Peer-to-peer networks are usually found in homes and small offices
97
What is the maximum number of workstations supported on a peer-to-peer network?
Peer-to-peer networks can support a maximum of 10 workstations. Therefore, they aren't suitable for larger organisations
98
How do devices connect on a peer-to-peer network?
On a peer-to-peer network, all devices are equal and connect directly to each other, without a server
99
How are files stored on a peer-to-peer network? What can you do with them?
Files are stored on individual devices and you can then share them with others
100
Give one way a peer-to-peer network may be used in a home
A P2P network may be used at home to: share files between devices, or connect devices to a printer
101
With a peer-to-peer network, there is no central file server. So, how are files stored?
Instead, files are stored on the hard disk of each workstation
102
Files and folders are assigned shared permissions. Describe how users can interact with files on a peer-to-peer network.
Files and folders are assigned shared permissions. They are to be shared with other users on the network.
Users can access those directly from the workstation, where they are stored.
103
Give three advantages of client-server networks
Advantages of Client Server Networks:
- Because resources are stored on the file server, rather than individual workstations, users can log onto any computer on the network and access their files
- Backups can be made centrally from the file server, instead of having to go to each workstation
- Software and updates can also be installed from the central server
- Both of these save time and ensure that nothing is missed
104
Give three disadvantages of client-server networks
Disadvantages of Client Server Networks:
- The networks need specialist knowledge to set up
- They need specialist staff to maintain them, like a network manager
- This makes them the more expensive of the two architectures
- If the central file server is unavailable, no one on the network can access their files
- If the print server goes down, nobody can print any documents
- The server is a single point of failure. This can be frustrating to the users and expensive for the organisation because of lost productivity
105
Give three advantages of peer-to-peer networks
Advantages of Peer-to-Peer Networks:
- Peer-to-peer networks are very easy to maintain
- Peer-to-peer networks are easier to set up than client server networks. Although some technical knowledge is needed, you don't need specialist staff to keep them running.
- Because they do not need specialists to run and maintain the network, peer-to-peer networks are cheaper to set up
- No expensive hardware is required - making it cheaper
- There is no dependency on a single computer, if one stops working, the rest will still function
106
Give three disadvantages of peer-to-peer networks
Disadvantages of Peer-to-Peer Networks:
- Unlike with a client-server network, users on a peer-to-peer network don't have to log in. The only security is whether the user knows the password to the protected file.
- If the network printer is running from an unavailable peer, nobody can print any work.
- With peer-to-peer networks, backups have to be made directly from each individual workstation.
- Software updates have to be done on each individual workstation
107
Give four pieces of hardware needed to set up and run a computer network
Some of the hardware needed to set up and run a computer network are:
Network nodes (Devices)
Network Interface Card (NIC)
Switch
Router
Transmission Media (Cables)
Wireless Access Point (WAP)
108
What types of connection do NICs exist for?
NICs exist for both wired and wireless connections
109
Network Interface Cards used to be on separate cards. How are they put into a computer now?
They used to be on separate cards, but are built into the motherboard nowadays
110
What is a Network Interface Card (NIC)?
A NIC is an internal piece of hardware that allows a device to connect to a network.
It converts data from the nodes into a format that is compatible with the network
In order to do this, it follows the network protocol (a set of rules)
111
What does the NIC follow, to convert data from the nodes into a compatible format for the network?
The NIC follows the network protocol - a set of rules
112
What is a hub?
A hub is a small box which links nodes together to form a network
113
How is every node on a wired network connected to a hub?
Every node on a wired network is connected to a hub by a cable
114
How do hubs transmit data? In what form do they transmit data?
Hubs transmit data from one node to another, in the form of data packets
115
What is a data packet?
A data packet is a small chunk of data. It has a destination address included
116
What happens to a data packet, when it arrives at a hub? Why is this not very secure?
When a data packet arrives at the hub, it is transmitted to every other node on the network.
This system of sending it to every node is not very secure though, because every node can view the data, whether it was intended for them or not
117
Explain what a data collision is, and how it occurs on a hub
Data collisions happen because a network cable can only have one data packet in it at any instant
So, if two or more computers on the network transmit data at exactly the same time, a data collision will occur
The collided data is marked as unusable and the data has to be transmitted again
This can lead to a delay and the network slowing down.
118
If two or more computers transmit data at exactly the same time, what will happen?
A data collision will occur
119
Why do data collisions happen?
Data collisions happen because a network cable can only have one data packet in it at any instant
120
Why is a switch similar to a hub?
A switch is similar to a hub because it allows computers to be linked together to exchange data
121
What is the purpose of a switch?
A switch receives data, in frames, from one device and transmits this to the device on the network with the correct MAC address
122
On what network does a switch connect devices?
A switch connects devices on a LAN
123
Why does the switch know the location of every node on the network? Why does this improve security?
The switch knows the location of every node on the network because of their individual MAC addresses. Because data is only sent to the intended devices, security is improved
124
Give an advantage of a switch
+ The switch knows the location of every node on the network because of their individual MAC addresses. Because data is only sent to the intended devices, security is improved
+ There is also a much lower risk of data collisi
125
What is the disadvantage of switches?
The disadvantage is that switches cost more than hubs, so switches tend to only be used in high bandwidth, high performance networks
126
Why do switches tend to only be used in high bandwidth, high performance networks?
Because switches cost more than hubs
127
Give a disadvantage of a hub
-When a data packet arrives at the hub, it is transmitted to every other node on the network.
This system of sending it to every node is not very secure though, because every node can view the data, whether it was intended for them or not
-Another issue with using a hub is the high risk of a data collision
Data collisions happen because a network cable can only have one data packet in it at any instant
So, if two or more computers on the network transmit data at exactly the same time, a data collision will occur
The collided data is marked as unusable and the data has to be transmitted again
This can lead to a delay and the network slowing down.
128
What is a router?
A router is a device which transfers data between networks
129
What do routers direct?
Routers direct data, in packets, to their destination
130
Routers are always connected to at least how many networks?
Routers are always connected to at least two networks
131
What do routers connect together, to form a WAN?
Routers are used to connect Local Area Networks (LANs) together to form a Wide Area Network (WAN)
132
Why are routers often used in homes and offices?
They are often used in homes and offices to connect the LAN to the Internet (a WAN)
133
What three things are most home 'routers' a combination of?
Most home 'routers' are a router, switch, and WAP all-in-one
134
Without a router, what would you not be able to do?
Without a router, you would not be able to connect to the internet
135
Describe how a router receives and sends a data packet
1. A data packet arrives from the node or hub
2. The router reads the data packet's destination IP address (internet protocol address) - this is not the same as the MAC address
3. The router uses a database to look up where the IP address is located
4. It identifies all of the different routes that could be used to send the data packet through
5. It checks how busy each route is at that very moment
6. It sends the data packet via the fastest route/path
136
What is the purpose of network cables?
Network cables are used to join individual nodes together to form LANs
137
Give one type of Ethernet cable
CAT-5
CAT-5e
CAT-6
138
Wired connections have a higher what, compared to wireless networks?
Wired networks have a higher bandwidth than wireless networks
139
What are Ethernet cables used to connect?
Ethernet cables are used to connect devices in a LAN
140
What are the two most common Ethernet cables?
The most common ethernet cables are CAT5e and CAT6
141
Ethernet cables are 'twisted pair' cables. What does this mean? Why is this an advantage?
Twisted pair cables contain four pairs of copper wires which are twisted together to reduce internal interference
142
What are coaxial cables made of? Why is this an advantage?
Coaxial cables are made of a single copper wire, surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference
143
What are fibre optic cables used for?
Fibre optic cables can be used to connect WANs or large LANs together. Fibre optic cables use light to transmit data.
144
Fibre optic cables are used underwater. Why?
They are used in undersea cables to carry internet traffic between continents.
Because fibre optic cables are able to cover much longer distances than copper cables without losing signal quality.
145
What do undersea cables do?
Undersea cables carry internet traffic between continents
146
What are fibre optic cables made of? How do they send data?
Fibre optic cables are tiny strands of glass. They send data as light
147
Give an advantage of fibre optic cables
Fibre optic cables are able to cover much longer distances than copper cables without losing signal quality.
These provide very high bandwidth and a very fast speed.
148
What is the disadvantage of fibre optic cables?
The disadvantage is that they are more expensive compared to standard Ethernet (copper) cables
149
What network do copper cables tend to be used on?
Copper cables tend to be used on LANs
150
There are different types of copper cable. What do more expensive copper cables offer?
More expensive copper cables can carry additional data at a faster speed
151
Give two disadvantages of copper cables
Susceptible to interference from magnetic fields or electromagnetic radiation
Can be more expensive than fibre optic cables or wireless
Susceptible to corrosion
They are heavy and bulky which can cause difficulty when installing
152
What is the purpose of a Wireless Access Point (WAP)?
A wireless access point (WAP) is used to connect Wi-Fi devices to a wired network, without the need for physical cables
153
Where are WAPs commonly found?
WAPs are commonly found in homes and also in public areas, like cafes, airports, offices, etc
154
To access a Wi-Fi hotspot, what do you need?
To access a Wi-Fi hotspot, you need:
the name of the network
the correct password
155
On a home network, there is a single box that has the role of a WAP, router, and a switch. What is it connected to? Who is it usually provided by?
It is connected to the telephone network and is usually provided by the Internet Service Provider (ISP)
156
What is the main advantage of a Wireless Access Point (WAP)?
On larger networks, a WAP can provide access to the network without the need to be physically connected with cables.
As long as people are within range of the WAP, they can move about from room to room and still be able to access the network
157
Why are WAPs similar to hubs? Why is this quality a security issue?
WAPs are similar to hubs. They do not read the destination address (MAC) of the data packet. They simply broadcast the data to every device connected to the Wi-Fi network.
This is a security issue as anyone connected to the network can access the data.
158
Give a disadvantage of a WAP
WAPs do not read the destination address (MAC) of the data packet. They simply broadcast the data to every device connected to the Wi-Fi network. This is a security issue as anyone connected to the network can access the data.
The bandwidth on a wireless network is less than a wired or cabled network.
159
What is a protocol?
A protocol is an agreed set of rules for how devices communicate and how data is transferred across a network
160
What three things do protocols cover?
Protocols cover:
How communication between two devices should start and end
How the data should be organised
What the devices should do if data goes missing
161
What is the purpose of Transmission Control Protocol/Internet Protocol (TCP/IP)?
Communicate over LANs and WANs
162
What is the purpose of Hypertext Transfer Protocol (HTTP)?
Used by web browsers to access websites and communicate with web servers
163
Why is Hypertext Transfer Protocol Secure (HTTPS) different to Hypertext Transfer Protocol (HTTP)?
It is a more secure version of HTTP. It encrypts all information sent and received. It also includes authentication.
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What is the purpose of File Transfer Protocol (FTP)?
Used to access, edit, and move files between devices on a network, for example to access files on a server from a client computer
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What is the purpose of Post Office Protocol - Version 3 (POP3)?
Used to receive emails from a server. The server holds the email until you download it, at which point it is deleted from the server
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What is the purpose of Internet Message Access Protocol (IMAP)?
Used to retrieve emails from a server. The server holds the email until you actually delete it - you only download a copy. Used by most web-based email clients
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What is the purpose of Simple Mail Transfer Protocol (SMTP)?
Used to send emails. It is also used to transfer emails between servers
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What is the difference between Post Office Protocol - Version 3 (POP3) and Internet Message Access Protocol (IMAP)?
POP3 is used to receive emails from a server. The server holds the email until you download it, at which point it is deleted from the server.
IMAP is used to retrieve emails from a server. The server holds the email until you actually delete it - you only download a copy. Used by most web-based email clients.
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What should a good protocol include?
A good protocol should include:
How to set up and end a connection
How to start and end a message
How to deal with corrupted data
How to format the data being sent
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What is Internet Protocol (IP) responsible for in Transmission Control Protocol/Internet Protocol (TCP/IP)?
IP (Internet Protocol) is responsible for packet switching
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What information does TCP/IP ensure packets have?
TCP/IP is the set of protocols used over the internet. It organises how data packets are communicated and makes sure packets have the following information:
Source - which computer the message came from
Destination - where the message should go
Packet sequence - the order the message data should be re-assembled
Data - the data of the message
Error check - the check to see that the message has been sent correctly
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Explain the function of Transmission Control Protocol (TCP)
TCP (Transmission Control Protocol) sets the rules for how devices connect on the network.
It's in charge of splitting data into packets and reassembling the packets back into the original data once they reach the receiving device.
It's also responsible for checking the data is correctly sent and delivered
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When sending data, what do the TCP rules include?
When sending data, the TCP rules include:
Dividing the message into packets
Adding a sequence number of each packet
Adding extra error-correction information
When receiving data, the TCP rules include:
Examining each packet, checking for errors
Fixing any errors, or requesting a packet to be resent
Spotting missing packets and requesting them to be resent
If everything is there and correct, it re-assembles the message
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When transmitting the message, what is the Internet Protocol (IP) responsible for?
When transmitting the message, the IP is responsible for providing the destination address and recognising incoming data packets.
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For sending data packets, what do the Internet Protocol (IP) rules include?
For sending data packets, the IP rules include:
Adding the destination address to each packet
Adding its own address to each packet
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For receiving data packets, what do the Internet Protocol (IP) rules include?
For receiving data packets, the IP rules include:
Accepting data packets that have its own address attached to the destination
Ignoring all data packets that do not have its own address attached to the destination
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Why is layering used?
Layering is used to divide the complex task of networking into smaller, simpler tasks that work with each other
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What does the hardware and/or software for each layer have?
The hardware and/or software for each layer has a defined responsibility
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What does each layer provide to the layer above it?
Each layer provides a service to the layer above it
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Give 4 advantages/reasons for layering
Reasons for and Advantages of layering:
- Reduces the complexity of the problem into manageable sub-problems
- Products from different vendors will work together
- One layer can be changed without affecting the others
- Separates tasks so they can be developed independently
- A developer can focus on only one layer
- Allows for standards for individual tasks/layers to be developed Manufacturers can develop hardware to fit into one particular layer
- To group together similar protocols
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Layer 4: Application Layer:
What protocols are included in this layer? What is the purpose of this layer?
Protocols: FTP, HTTP, POP, IMAP, SMTP
Purpose: The protocols in this layer provide access to email, files and websites across an IP network
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Layer 3: Transport Layer:
What protocols are included in this layer? What is the purpose of this layer?
Protocols: TCP
Purpose: The TCP part of the TCP/IP protocol resides in this layer. It is responsible for dividing messages into packets, adding sequence numbers and error correction information. It also checks and deals with errors of received data packets.
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Layer 2: Internet Layer:
What protocols are included in this layer? What is the purpose of this layer?
Protocols: IP
Purpose: The IP part of the TCP/IP protocol resides in this layer. It is responsible for managing the address of source and destination locations.
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Layer 1: Network/Data Link Access:
What protocols are included in this layer? What is the purpose of this layer?
Protocols: Ethernet, Wi-Fi
Purpose: The protocols in this layer are responsible for actually transmitting and receiving data through cable or wireless
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Give three advantages of the Four Layer Model
Advantages of the Four Layer Model:
- By dividing the system of protocol into layers, we can focus on one layer without worrying about the other three
- It is useful for manufacturers when developing new hardware - they can ensure it is compatible with existing protocols
- We can map how layers relate and interact with each other
- We can recognise roughly what the purpose of a protocol is, by knowing the layer it is in
- When a new protocol is developed, it can be added to the appropriate layer
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What is network topology?
Network topology is the layout of connections in a network
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What is each device in a network topology called?
Each device within a network is called a 'node'
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Give two examples of a node
A node can be:
A workstation, tablet, printer, server, etc
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How do nodes connect to other nodes on a network?
Nodes connect to other nodes on the network either by physical cables or Wi-Fi
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The star network topology has a central device. What three things could this device be?
The device can be a hub, switch, or a server
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The star network topology has a central device. What does this do?
This central device connects directly to every other node on the network, forming a star-like shape
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In a star topology, what are all devices connected to?
In a star topology, all the devices are connected to a central switch or server that controls the network
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Give one reason why star topologies are often used by small organisations
Star network topologies are often used by small organisations because they are:
Efficient
Low cost to set up and run (on a small network)
Simple to set up (on a small network)
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Give two advantages of star topologies
Advantages of Star Topologies:
- Star networks are reliable - if one connection fails, it does not affect other users on the network
- Data collisions are rare - this is because each node has its own cable connecting it directly to the central node or device
- Star networks offer good security - this is because no workstation can directly interact with another without going through the central node first
- Scalability - it is an fairly simple process to add or remove a node in a star network. Doing so, does not have any effect on the other nodes
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Give two disadvantages of star topologies
Disadvantages of Star Topologies:
- Require technical expertise - a small star network is straightforward to set up. However, a large star network will need someone with specialist knowledge to set up and run it.
- Network failure - if the central switch or server fails, the whole network will go down and nobody will be able to use it
- Equipment - a star network requires a high performance server or switch as all traffic passes through these points
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A mesh topology, unlike a star topology, doesn't have what?
A mesh network topology, unlike a star, has no central node
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Instead of every node being connected to a central device, how is each node connected on a mesh topology?
Each node is connected to every other node on the network - it is decentralised.
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In terms of sending data, how do mesh networks work?
Mesh networks work by sending data along the fastest route from one device to another
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Explain why not having a central device can be an advantage for a mesh topology
There is no single point where the network can fail.
If the central switch or server of a star network fails then the whole network fails — in a mesh network, if one device fails then the data is sent along a different route to get to its target.
200
The traditional problem with mesh networks is that they were very expensive. Why was this? Why is this changing?
The traditional problem with mesh networks has been that they were very expensive because you needed a lot of wire to connect so many devices together.
But now, more people are using wireless technology, mesh networks are a more practical option.
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What is a full mesh topology?
A full mesh topology is where every device is connected to every other device
202
What is a partial mesh topology?
A partial mesh topology is where not all devices are fully-connected
203
Give two examples of where a mesh topology is often used
A mesh topology is often used in military organisations, cities, emergency services, etc
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Give three advantages of mesh topologies
Advantages of Mesh Topologies:
- A mesh network is reliable and robust - if one node fails, then other nodes within range allow data transmission to continue around the network
- Mesh networks can handle high data traffic rates
- Data packets can be sent simultaneously around a mesh network
- Devices can easily join, or leave, the network without affecting the overall quality
205
Give three disadvantages of mesh topologies
Disadvantages of Mesh Topologies:
- The number of connections in the network will increase exponentially as more new nodes are added.
- As the size of the network increases, the cost of physically connecting nodes becomes prohibitive in terms of money and complexity.
- Security - because data is transmitted throughout the network using Wi-Fi, there may be issues with data security.
- Many mesh topologies will require a lot of maintenance
206
How are devices arranged in a bus topology?
In a bus topology, all devices are arranged in a line, connected to a single backbone cable
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What is the cable called in a bus topology?
The bus topology's only cable is called the backbone cable
208
In what direction(s) is/are data sent in a bus topology?
In a bus topology, devices send data in both directions
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In a bus topology, devices send data in both directions. Why is this a problem?
This causes data collisions, which slows the network
210
In what direction(s) is/are data sent in a ring topology?
In a ring topology, devices send data in one direction, around the ring
211
In a ring topology, devices send data in one direction, around the ring. What does this prevent? But what is the disadvantage?
This method of sending data prevents data collisions
But only one device can send data at a time and data passes through many devices before reaching its destination
212
Give three things that can be connected to the internet
Things connected to the internet:
Phone
Tablet
Laptop
Computer
Smartwatch
Smart TV
Gaming consoles
Personal Digital Assistant
213
What is a network?
A network is two or more computing devices connected together, so they can share resources
214
What are the two types of network?
Local Area Network (LAN)
Wide Area Network (WAN)
215
For a LAN to be created, what must happen?
For a LAN to be created, the network devices need to be located near to one another
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What is a LAN?
A LAN is network devices connected in close proximity, on a single site
217
Who owns all the hardware for a LAN?
All hardware for a LAN is owned by the organisation that uses it
218
What type of connection(s) does/do LANs support?
LANs are either wired or wireless
219
Give two places where LANs are common
LANs are common in businesses, schools, and universities
220
Give two methods devices can be connected together on a LAN
Devices are connected together using either:
Copper ethernet cables
Wi-Fi
221
What does a WAN connect?
A WAN connects two or more LANs, that are in different geographical locations, together
222
Give an example of where a WAN can be used. Why would this help?
For example, a company may have offices in London, Paris, Rome, New York, etc.
A company WAN will enable staff from different offices to share files and resources stored on the network.
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What area do WANs cover?
WANs cover a large geographical area
224
What is a WAN?
A WAN is two or more LANs connected together
225
Who owns the infrastructure for a WAN? Why?
Organisations hire infrastructure from telecommunications companies, who own and manage the WAN.
This is because a WAN is much more expensive to set up than a LAN.
226
What is the largest WAN in existence?
The internet is the largest WAN in existence
227
LANs are connected to form WANs using different methods. Give two of these methods.
LANs are connected to form WANs using different methods, these include:
Fibre optic cables
Telephone lines
Satellite communication links
Microwave links
228
Give two disadvantages of networking
Disadvantages of Networking:
- Increased security risks to data
- Malware and viruses spread very easily between computers
- If a server fails, the computers connected to it may not work
- The computer may run more slowly if there is a lot of data travelling on the network
229
Give four advantages of LANs
Advantages of LANs:
- Resources and files can be shared by users on the LAN
- Users can log onto any workstation on the network because user accounts are stored centrally
- Peripherals, such as printers, can be shared by users on the LAN
- Backups can be made centrally
- The internet connection can be shared between every device connected to the LAN
- Software can be installed centrally
- Network users can access the same files and work collaboratively on them
230
Give two disadvantages of LANs
Disadvantages of LANs:
- Risk of network failure
- High cost
- Support staff needed
- Risk of viruses and malware
231
Give two advantages of WANs
Advantages of WANs:
- They enable LANs to be connected together
- They enable data to be shared between LANs
- They allow workers to collaborate, even if they are geographically far apart
232
Give three disadvantages of WANs
Disadvantages of WANs:
- Risk of network failure
- High cost - even higher than a LAN
- Larger risk of viruses and malware
- Support staff needed
- More expensive to set up than a LAN
233
Describe, in detail, how packets are sent
Sending Packets:
1. Data sent between networks is split into equal-sized packets.
2. Every data packet has a header — this contains the control information. The control information includes the packet's destination address, the source address, and the packet number.
3. The data packet's payload is the thing a person is likely to read, and the whole reason the data packet has been sent in the first place. The payload might be part of an email, document, web page or streamed video.
4. Packets are also likely to include a checksum number — a form of validation used to check that the payload data hasn't been corrupted during transit. The sending and receiving devices both calculate a checksum value by performing a function on the payload data. If the values match then the data has been received correctly.
234
Describe, in detail, the process of packet switching
Packet Switching:
1. The sending device splits the data into packets to be sent across the network. Each packet is given a packet number to show the order of the data.
2. Each router reads the packet header and decides which way to send the packet next, according to the IP rules
3. The way the data is sent changes depending on network traffic, so the packets can take different routes. If a router receives too many packets at once, it may prioritise some over others.
4. As the packets take different routes, they can arrive in the wrong order. The receiving device uses the packet numbers to reassemble them in the right order.
5. Sometimes, packets go missing in transit, so the receiving device checks periodically that all packets have been received. If it hasn't received them within a certain time, it sends a timeout message back to the sending device.
6. If all the data is received and the checksums match, a receipt confirmation is sent to the sending device.
235
Why is packet switching used by routers?
Packet switching is used by routers to direct data packets on the Internet and other IP networks
236
What device is packet switching used by?
Packet switching is used by routers
237
Why is packet switching an efficient use of a network?
Packet switching is an efficient use of a network because there are so many possible routes that data can take — packets can reach their receiving device even if there's heavy traffic
238
Give two factors that can affect the performance of networks
Factors affecting the Performance of Networks:
- Network performance is how well data is transmitted throughout a network.
- The speed of a network is measured in 'bits per second'
- The two types of connection that can be used, when connecting to a network are wireless and wired.
- Choice of hardware other than cables, and network topology also have a big effect.
239
What is bandwidth?
Bandwidth is the amount of data that can be sent and received in a given time
240
Describe the relationship between bandwidth and network performance
The greater the bandwidth, the better the network can perform
241
What is bandwidth measured in?
Bandwidth is measured in bits per second
242
What is bandwidth often called?
Bandwidth is often called bit rate
243
Between users, what is done to available bandwidth?
Available bandwidth is shared between users of a network
244
If there are too many users, or the network is being used heavily, what can happen?
If there are too many users, or there is heavy use - for example streaming videos - it can cause congestion and slow the network
245
If there are too many users or the network is being used heavily, it can lead to congestion and a slower network. What is the solution to this?
You can limit the available bandwidth for individual users
246
Networks are built to support many users. The bandwidth has to be shared amongst the users. Does this have to be done equally?
Bandwidth does not always have to be shared equally amongst users on a network
247
What is the contention ratio used to measure?
The contention ratio is used to measure the ratio of users compared to the available bandwidth
248
What does the type of cable or signal chosen for a network, have an impact on?
The type of cable or signal chosen can affect the network performance
249
Give two disadvantages of Wi-Fi
Wi-Fi has a lower bandwidth compared to Ethernet cables so less data can be supported
Data may be transmitted at a slower rate, thus affecting network performance
Wi-Fi is prone to more errors with interference from other signals and packets becoming lost.
250
What is the main advantage of Wi-Fi?
Wi-Fi allows devices to be moved around. It is a wireless network. The devices do not have to be connected by a cable
251
Wi-Fi has two radio frequency bands. What are they?
2.4GHz and 5GHz
252
In terms of range, compare Wi-Fi's 2.4GHz and 5GHz bands
2.4GHz has a greater range and is better at getting through walls and other obstructions.
5GHz is faster over short distances.
253
Describe how the Wi-Fi bands are split
The bands are split into numbered channels that each cover a small frequency range
254
What happens to the channels in the 2.4GHz Wi-Fi band?
The channels in the 2.4GHz band overlap
255
What is Wi-Fi performance affected by?
Wi-Fi performance is affected by interference between networks using adjacent channels
256
Wi-Fi performance is affected by interference between networks using adjacent channels. How is this problem avoided, using Wi-Fi bands?
To avoid problems, only certain channels that are spaced apart tend to be used.
The 5GHz band has more non-overlapping channels than the 2.4GHz band, so there's less chance of interference.
257
The 5GHz Wi-Fi band has more non-overlapping channels than the 2.4GHz band. Why is this an advantage?
More non-overlapping channels results in a lower chance of interference
258
What is error rate?
Error rate is the number of errors that occur during data transmission
259
Describe when an error can happen, when sending data
An error can happen when, for example, a binary 1 is sent across the network, but instead, a binary 0 is received
260
In the event of an error when sending data, what must happen?
In the event of an error, the data must be re-sent
261
What are the two reasons why an error can happen, when sending data?
An error can occur due to:
Interference
Weak signal
262
If a cable, or switch, is placed in close proximity to electrical equipment, for example motors, what can happen?
Interference from the equipment may cause the bits to flip randomly.
263
Interference from equipment may cause bits to be flipped randomly. What can be used to reduce this problem?
Shielded cables can be used to reduce the problem
264
As the cable length gets longer, what can happen to the signal? Why is this a problem?
As the cable length gets longer, the signal can become too weak and errors can begin to creep in
265
What is latency?
Latency is how much time it takes for a packet of data to travel across the network
266
Why is latency not really a problem, on a small LAN?
On a small LAN, latency is not really a problem because all of the nodes are near one another
267
Why can latency be more of an issue on a larger network, like a WAN?
Every cable, switch, and router on the network adds a delay (latency), to the connection
268
What are high latency networks?
High latency networks are networks with long delays
269
Give an advantage and disadvantage of a wired connection
Wired networks are better because they can carry data directly to the device, resulting in a faster speed and less interference because it cannot be blocked by walls, and doesn’t need to find Wi-Fi signals.
But, they are less portable, the cable has to be plugged into the device.
270
Wired networks are better because they can carry data directly to the device. Why is this an advantage?
It results in a faster speed and less interference because it cannot be blocked by walls, and doesn’t need to find Wi-Fi signals
271
What two things can cause interference?
Walls and electrical objects can cause interference
272
On a wireless network, other than interference, what can a weak signal be caused by?
A weak signal can be caused by being too far away from the router
273
What is the data packet's payload?
The data packet's payload is the thing a person is likely to read, and the whole reason the data packet has been sent in the first place.
The payload might be part of an email, document, web page or streamed video
274
Packets are likely to include a checksum number. What is a checksum number? Describe how it is used
A checksum number is a form of validation used to check that the payload data hasn't been corrupted during transit.
The sending and receiving devices both calculate a checksum value by performing a function on the payload data.
If the values match then the data has been received correctly.
275
Describe how the sending and receiving devices calculate a checksum value. How do they use it to determine if the data has been correctly received?
The sending and receiving devices both calculate a checksum value by performing a function on the payload data.
If the values match then the data has been received correctly
276
Every data packet has a header. What does a header contain?
The header contains the control information.
The control information includes the packet's destination address, the source address, and the packet number.
277
During packet switching, if the receiving device hasn't received packets in a certain time, what happens?
The receiving device sends a timeout message back to the sending device
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