Networks

• A network is a collection of devices that are connected to one another.
• A LAN has a smaller geographical area and is owned/maintaned by a single person or organisation. It is faster, cheaper, easier to manage, leads to less congestion, and typically has higher bandwidth but has a limited geographical range.
• A wired connection has faster transfer speeds and is less susceptible to interference but is more expensive and there's a lack of freedom of range of movement for devices.
• A wireless connection has greater range, it's easy to add new nodes, and you can move wherever within the range but it is weak to electromagnetic interference, wall blockages, and is more interceptable
• TCP stands for Transmission Control Protocol and IP stands for Internet Protocol.
• Wireless connections have slower transfer rates, they may be affected by interference from other sources (e.g. microwaves), and security issues such as unauthorised access.
• Network data speeds are measured in bits per second
• 1 byte = 8 bits
• Protocols are rules for communication amongst devices to ensure that devices can communicate and interact with one another. Especially when they are made by different companies.
• Examples of network protocols include: wifi, ethernet, HTTP(S), FTP, TCP, and IP
• Wifi is a wireless connection whereas ethernet is a wired connection
• HTTP is for accessing web pages made with HTML. Users type in a URL and the protocol conducts a request to the web server for the page. The page is then sent back into browser if found.
• URLs follow this format: protocol, domain name, page name
• HTTPS stands for Hypertext transfer protocol secure
• Wireless networks use radio waves to transmit data between devices
• HTTPS is used by websites that deal with sensitive information as it encrypts information so it is not understandable by eavesdroppers.
• HTTPS does not gurantee a website isn't trying to scam you, as any website can use HTTPS it just means the connection is secure.
• FTP, which stands for file transfer protocol, uses a client server model to send files to (uploading) and receive files from (downloading) the FTP servers.
• HTML stands for hyper text markup language
• IP stands for internet protocol
• IP is the protocol that deals with sending data from one computer to another. It is in charge of: routing and addressing data packages so they arrive at the intended recipient/computer.
• There are 4 layers in the network model: Application, transport, internet, and link
• Application layer uses HTTP(S), SMTP, POP3, IMAP, FTP.
• In the application layer apps create data to be sent by encoding and decoding it.
• In the transport layer, a connection between two computers is created. Data is then broken down into packets and those packets are assigned numbers. Lost packages also get resent.
• The transport layer uses tcp
• TCP does packet switching. On a packet, there are sections of data. The header which contains the IP address, packet number, number of packets, and protocols used.
• On the payload of a packet the part of the message or data in the packet is contained.
• Routing packages (and so routers operate on this layer) occurs on the intternet layer. There's the source and destination of packages.
• Packets can take different routes from one computer to another because they have multiple paths available. This means that if one path fails, the package will go through an alternative route.
• IP addresses are unique identifiers given to devices connected to the internet. They consist of four sets of digits separated by dots. Each set has values ranging from 0-254.
• IP is used on the internet layer
• On the Link layer: MAC/Ethernet/Wifi is used and transfer of packets between nodes on network occur here.
• The relevant email procotols are: 1. SMTP 2. POP3 3. IMAP
• POP3 is good for travelers or people who don't always have internet connectivity as the emails received through POP3 are downloaded onto a device and always readily accessible.
• In pop3, changes made to emails aren't shown on other devices. Furthermore emails must be downloaded before they can be read.
• IMAP allows users to access their emails across multiple devices without having to download them first. Changes made to an email will show up on all devices that use the same account. However it requires constant connection to the server which may not be possible if there isn't any internet connectivity.
• IMAP is good for people who use multiple devices interchangeably to handle emails.
• Emails get sent to mail server using SMTP and then are forwarded by more SMTP servers till it reaches the destination mail server. Computers will then use either POP3 or IMAP to access the email.
• Network topologies include bus topology, star topology, and mesh topology.