1.3 - Computer networks, connections and protocols (Part 2)

Wired vs Wireless

- Wired connections are physical cables that connect two devices together.
- Wired connections are generally more reliable and faster than wireless connections, but wireless connections are more secure and can be used over longer distances.
- The most common type of wired connection is the twisted pair cable, explained in 3_1, and Ethernet is the most common use of twisted pair cables for LANs, as it is standardised and well-supported.
- Ethernet can send and receive data simultaneously, through each pair of wires, at speeds of up to (most commonly) 10 Gbps (gigabits per second).
- Wireless connections are a type of network connection that uses radio waves to transmit data between devices.
- Wireless connections use radio waves to transmit data, and are more flexible and can be used in more situations.
- Wireless connections can be used in places where wired connections are not possible, such as in the open air, or in areas with poor or no coverage.

Feature Wireless Wired
Mobility High mobility, can move freely Limited by cable length
Setup Complexity Usually simpler, no cables required Can be complex with multiple cables
Interference Prone to interference from other wireless devices Less prone to interference
Data Transfer Speed Can be slower due to signal loss or interference Generally faster and more stable
Power Consumption Higher, especially for portable devices Lower, as it typically relies on device power
Reliability Can be affected by distance and obstacles More reliable due to direct connection

Types of Wireless Connections

- For GCSE, you need to know about WiFi and Bluetooth.
- WiFi, Wireless Fidelity, or 802.11, is a very common standard for wireless connections, and is most common to connect to devices such as laptops, smartphones, tablets, and TVs.
- Clients using WiFi connect to a Wireless Access Point (WAP), which can be its own thing but is most commonly part of a router.
- Bluetooth is another standard for wireless connections, and is used for connecting devices together, such as a laptop and a mouse.
- It is much less commonly used for internet connections than WiFi.
- Bluetooth is only typically used for a connection between just two devices.

Feature Wi-Fi Bluetooth
Range Up to 100 meters Typically up to 10 meters
Data Transfer Speed Up to 1 Gbps (Wi-Fi 6) Up to 3 Mbps (Bluetooth 5.0)
Power Consumption Higher Lower
Use Cases Internet connectivity, file transfer, streaming Peripheral connections (headphones, keyboards), file transfer
Interference Can be affected by other Wi-Fi networks Less susceptible to interference, but can be affected by physical obstacles
Security Higher security with WPA2/WPA3 Lower security, but still secure with pairing

Encryption

- Encryption is the process of converting data into a code that can only be read by someone with the correct key.
- Encryption is used to protect data from being read by unauthorised parties.
- Encryption is important on both wired and wireless networks, but it is needed more on wireless networks due to man-in-the-middle attacks where someone can pretend to be the router and intercept data.
- Encryption is used to protect data in transit, and is also used to protect data at rest.

How is data encrypted?

- Encryption is done using a key, which is a piece of data that is used to encrypt the data.
- The key is used to encrypt the data, and the encrypted data is sent to the recipient.
- The key is kept secret, and only the recipient has the key to decrypt the data.
- Encryption is done using a specific algorithm, which is a set of rules that define how the data is encrypted.

Types of Encryption

- Symmetric encryption is where the same key is used to encrypt and decrypt the data.
- Asymmetric encryption is a different key is used to encrypt than to decrypt the data. This is also known as public key cryptography, and is what your computer is using to visit this website (assuming HTTPS, the 'S' stands for 'Secure').
- Hashing is a type of encryption where the data is converted into a fixed-length string of characters, which is called a hash.
- Hashing is used to verify the integrity of the data, and is also used to create digital signatures.

Encryption on wireless networks

- Encryption on wireless networks is done using WPA2/WPA3, however older standards like the original WAP still exist.
- When your computer connects to a wireless network, it will ask you for a password. This password is used, along with the network's SSID ('Service Set Identifier', or the network name), to encrypt the data by turning it into 'ciphertext' and back out again.
- The master key is sent to any device able to provide the correct password.
- The lack of encryption is the reason unsecured networks (ones without a password) are dangerous to use without another encryption standard. For websites this is TLS (Transport Layer Security) over HTTPS (although many websites that require you to enter passwords force you to use HTTPS to stay compliant with data protection laws).
- Encryption on wireless networks is used to protect the data from being intercepted by someone who is not the owner of the network, and is also used to protect the data from being read by someone who is not the owner of the network.

Encryption on wired networks

- Encryption on wired networks is done using WEP, which works in a similar way to WPA2/WPA3.
- It is a weaker standard than WPA2/WPA3, and so WEP should not be used for wireless networks which are easier to intercept.


IP addresses and MAC addresses

- IP and MAC addresses are used to identify devices on a network, and are used to route data between devices on a network.

IP addresses

- An IP address is a unique identifier for a device on a network.
- It is used to route data between devices on a network.
- It stands for 'Internet Protocol Address', and there are both internal and external IP addresses.
- An external IP address is the IP address that is visible to the internet, and is used to connect to websites and other services.
- An internal IP address is the IP address that is used to connect to devices on the same network, and is used to connect to services on the same network.

IPv4 vs IPv6

- IPv4 is the older commonly used IP address version.
- In IPv4, addresses are represented as a series of numbers separated by full stops, for example 81.0.246.142. They are 1 byte (8 bits) per block, so 32 bits overall.
- IPv4 requires internal IP addresses due to there not being enough addresses for each computer to have its own external IP address. This works through NAT (Network Address Translation), which is a process where the router translates the internal IP address to an external IP address, and the external IP address is visible to the internet.
- IPv6 is the newer commonly used IP address version.
- In IPv6, addresses are represented as a series of numbers separated by colons, for example 2a02:c204:2208:8374::1.
- IPv6 is needed due to there only being 4.3 billion IPv4 addresses available, which we ran out of in November 2019 (at least for RIPE NCC, who are the organisation that manages IP addresses for Europe, the Middle East and Central Asia. They were the last regional registry to run out.)
and so the number of IPv6 addresses is much higher (2^128 addresses, or, uh, 340,282,366,920,938,463,463,374,607,431,768,211,456.)
- If you get asked for an IPv6 in an exam, you may write '::1' which is simply the loopback address, which is the address of the computer itself, or an alias for 'localhost'.
- IPv6 addresses are varying length because ':0000:' can be compressed to just :: as many times over as needed, but only once per address (for example, 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is the same as 2001:0db8:85a3::8a2e:0370:7334, but if you had 2001:0db8:85a3:0000:0000:8a2e:0000:7333 you couldn't compress it to 2001:0db8:85a3::8a2e::7333, just 2001:0db8:85a3::8a2e:0:7334). Consecutive 0s can be compressed to just one 0.

If you are struggling to understand this, that's totally fair and don't stress about it too much, just remember ::1 is valid in case it comes up and remember that this is only a small part of the overall paper 1. Feel free to skip this section.

MAC addresses

- A MAC address ('Media Access Control Address') is a unique identifier for a device on a LAN.
- A MAC address is static, and one is usually assigned to a NIC at the factory and doesn't change no matter what network it's on.
- A MAC address is 12 hex digits (48 bits), grouped into pairs for readability. The first three pairs are the Organisation Unique Identifier (OUI), which is a unique identifier for the manufacturer of the device. The last three pairs are the Device Identifier, which is a unique identifier for the device itself.
- There are 281 trillion MAC addresses.
- An example of one is 00:0C:29:D5:B1:C8.


Standards

- I've talked quite a bit about standards already, so what actually are they?
- In computing, a standard is a set of guidelines that define how something should be done, and how it should be done.
- Standards allows hardware/software to interact across different manufacturers/producers.
- A standard is usually defined by a body, such as a committee or a group of people.
- They allow different hardware and software to be interchangeable, interoperable, and compatibility and allow for greater consistency and reliability.
- There are many standards bodies in computing.
- For example, IEC 60417-5009 is the name of the standard for the standby symbol, HTTP/2 (made by the IETF) is one of the HTTP versions you're most likely using to view this webpage (more on HTTP later), and the USB standards (by the USB-IF) define how USB devices should work.
- (you don't need to know this for GCSE, but the IEC stands for 'International Electrotechnical Commission', the IETF stands for 'Internet Engineering Task Force', and the USB-IF stands for 'USB Implementers Forum').


Protocols

- A protocol is a (standard) set of rules that define communication between two or more devices.
- The ones you need to know about are:

TCP/IP

- TCP/IP is the set of two protocols that allow computers to communicate with each other over the internet.
- TCP (Transmission Control Protocol) is the protocol that allows data to be sent without errors, or if there are errors, they are detected and corrected.
- IP (Internet Protocol) is the protocol that tells systems at the internet layer how to route data between computers. This is why IP addresses exist, or the internet layer would have no idea where to send traffic.

HTTP(S)

- HTTP allows clients and servers to communicate with each other with standard error codes and headers to view websites and access web resources.
- HTTP allows 'methods' to allow data to be transferred. For example, GET is used when requesting a resource, and POST is used when sending data to a server.
- (sidenote: if you press F12, go to the 'Network' tab, and reload, you can see the GET requests your computer is making for the resources on this page, and the (hopefully) 200 OK responses it gets back.)
- HTTPS is the same as HTTP, but it is encrypted so that no one except the intended recipient can read it.

FTP

- FTP is a standard optimised for file transfer between computers.
- Uploading/downloading files is often done through FTP due to its greater efficiency, and the ability to pause/resume downloads helps reliability, so you don't have to restart everything if you lose connection (like you might when downloading a large file over HTTP).
- Programs like FileZilla can be used to transfer files over FTP.

POP, IMAP and SMTP

- POP (Post Office Protocol) is a standard for email.
- IMAP (Internet Message Access Protocol) is a standard for email.
- SMTP (Simple Mail Transfer Protocol) is a standard for email.
- POP, IMAP and SMTP are all used to send and receive email.

(ok, to be more specific...)

- You use SMTP to send emails to your SMTP server, which then uses SMTP to communicate with the recipient's POP/IMAP server through the internet. The recipient can then access the emails on their POP/IMAP server through their email client.
- SMTP is for communication between email servers and email clients, and between different email servers so you can send emails to people on other providers. You send emails over SMTP.
- IMAP is a protocol for downloading email to your email client, and so is POP. The difference is that POP deletes email after it has been downloaded, whereas IMAP does not.

Protocol Advantages Disadvantages
POP (Post Office Protocol)
  • Emails are downloaded to local storage
  • Works well with limited server storage
  • Can access emails offline
  • Emails are not synced across devices
  • Limited to one device for viewing emails
  • Risk of losing emails if local data is lost
IMAP (Internet Message Access Protocol)
  • Emails are synced across multiple devices
  • Messages are stored on the server
  • Organize and manage folders server-side
  • Requires constant internet connection for access
  • Consumes more server storage space
  • Potentially slower performance with large mailboxes

Layers (networks)

- A layer aims to represent different sub parts of a task to make it easier and more manageable.
- Layers are used to separate concerns, and make it easier to maintain/work on just one layer at a time.
- They allow for more flexibility and easier development, and allow people to specialise on working with the layer they have the most experience with.
- They make it easier to build on top of lower layers, and reuse existing infrastructure for different purposes.
- The TCP/IP protocol uses a 4-layer model (stack):