MYP Design Networks and the Internet Notes

A Network Is Just Devices That Agreed on Rules

1. A network is two or more devices connected so they can swap data, and the agreed rules for swapping it are called a protocol.
2. A LAN, local area network, covers one site such as your school or your flat, and the owner controls the cabling.
3. A WAN, wide area network, links sites across towns or continents over infrastructure somebody else owns, and the internet is the largest WAN there is.
4. The internet is a network of networks, while the web is only one service running on top of it, sitting alongside email, video calls and game servers.
5. Inside a LAN, a switch moves data between local devices and a router decides what leaves for the outside world.
6. Going wireless does not turn a LAN into a WAN, so the Wi-Fi at home is still a local area network.

Clients Ask, Servers Answer

1. A client is any device doing the asking: your phone, your laptop, the browser tab open in front of you.
2. A server is a computer whose job is to wait for requests and send back replies, usually a plain machine in a rack rather than anything exotic.
3. One server handles thousands of clients at once, which is why a popular site crawls when a lot of people ask at the same moment.
4. Peer to peer networks drop the middle: every device is both client and server, which is how file sharing and some video calls move data.
5. When your CAD tool saves to the cloud, your laptop is the client and a server in a data centre is holding the model.
6. Plenty of faults you blame on your own laptop are the server end being down, so check the service status page before you restart anything.

IP Addresses and Domain Names: Numbers People Cannot Remember

1. Every device on a network carries an IP address, a numeric label such as 192.168.1.14 that says where to deliver data.
2. Addresses beginning 192.168 or 10 are private, handed out by your own router and reused in millions of other buildings.
   1. Everything in your house usually shares a single public IP address, and that is the one a website actually sees.
3. The older IPv4 scheme ran out of numbers, so IPv6 exists with addresses long enough for every device on the planet to have its own.
4. A domain name such as ibo.org is a label people can remember that points at one of those numbers.
5. The domain name system is the lookup service that turns the name into the number, which is how a site can change servers without changing what you type.

What Actually Happens When a Page Loads

1. You type a name, and your device asks a domain name server for the matching IP address, which usually comes back in a few milliseconds.
2. Your browser opens a connection to that address and sends an HTTP request naming the page it wants.
3. The S in HTTPS means the whole conversation is encrypted, so anyone listening on the café Wi-Fi sees scrambled bytes rather than your password.
4. The server replies with HTML, and the browser then fires off fresh requests for every stylesheet, script, font and image that HTML mentions.
   1. A page carrying 80 photographs sets off roughly 80 more round trips, so shrinking your images changes load time far more than shortening your writing.
5. Data crosses the network in packets, small numbered chunks that may take different routes and get put back in order at the far end.

Wired or Wireless: The Trade You Are Making

1. Ethernet cable gives steady speed, low delay and no interference, and charges you for it by tying the device to a socket.
2. Wi-Fi gives freedom of movement and pays for it by sharing the air with every other device, thick wall and microwave oven nearby.
3. The 2.4 GHz band reaches further and passes through more walls, while the 5 GHz band is faster and gives up sooner.
4. Wireless capacity is shared, so twenty tablets on one access point each get a slice of whatever the cable behind it delivers.
5. Bluetooth is short range and low power, built for one device talking to one other, which suits a sensor reporting to a phone and not a file transfer.
6. Anything that must never drop out, such as a CNC machine receiving a job or a live presentation, belongs on a cable.

Bandwidth and Latency Are Two Different Complaints

1. Bandwidth is how much data fits through per second, measured in megabits per second, and it decides how long a big file takes.
2. Latency is the delay before the first bit arrives, measured in milliseconds, and it decides how responsive everything feels.
3. A satellite link can carry plenty of data and still have 600 ms of latency, which is fine for downloading a film and painful on a video call.
4. Games and calls break because of latency; a 2 GB component library downloads slowly because of bandwidth.
5. Home connections usually upload at a fraction of their download speed, which is why sending your folder takes far longer than browsing someone else's.

Cloud Storage Is Someone Else's Computer, and That Cuts Both Ways

1. Cloud storage keeps your files on a company's servers and syncs a copy onto every device you sign in on.
2. It fixes the real nuisance of design work: opening the same model on a studio desktop and a home laptop without a USB stick going missing in between.
3. Version history is the feature that rescues projects, because you can roll a broken assembly back to yesterday's working file.
4. A synced folder is not a backup: delete a file on one device and the deletion travels to every other device in seconds.
   1. Keep one copy that sync cannot reach, on a USB drive or an external disk, so a single bad click cannot end the project.
5. Cloud files also mean someone else is holding your work, so read what the terms say about who can see it and what happens when an account lapses.

Sharing Work With a Teacher or a Client

1. Send a link with view only permission when you want feedback, and edit permission only when you want changes made.
2. Check the link works from a signed out browser window, because a link that only opens on your own account is a link nobody else can use.
3. Export a flattened PDF of your folder alongside the live files, so the work survives a service going offline on the day it is read.