IB Digital Society 3.4B Components of Computing Networks Notes

3.4B Components of Computing Networks

The Building Blocks

1. A network depends on specialised components that move data; most are invisible (in a cupboard or street cabinet) yet nothing online works without them.
2. Components split into two kinds: edge components (modem, router) sit at the boundary with the outside world; internal components (switch, wireless access point) connect local devices to each other.

Modem and Router

1. A modem is the bridge to the outside world: it converts between the home network's signals and those on the provider's line, so it actually connects a household to the internet.
2. A router directs data between networks and shares one connection among many devices, working out where each piece of data should go so a phone, laptop, and TV can all use it at once.
   1. Often combined in one box, but the roles are distinct: the modem gets you onto the internet; the router shares and directs that access inside the home.

Hub and Switch

1. A hub broadcasts any data it receives to every connected device, whether or not it was the intended recipient: cheap and simple, but wasteful and less private.
2. A network switch reads each piece of data's destination and sends it only to the intended device: cuts traffic, speeds the network up, and keeps data private.
   1. Privacy difference: on a hub any device could listen in; a switch keeps each message to its intended path.
   2. Hubs have nearly vanished: signals collide and must resend as devices join, whereas a switch gives each device a dedicated path so many conversations run at once.

Wireless Access Points

1. A wireless access point lets wireless devices join a network and extends coverage, broadcasting over radio waves so phones and laptops connect across a room or building.
2. One access point covers a limited range, so large spaces use several with overlapping coverage; a moving device hands off from one to the next, ideally unnoticed.
   1. Trade-off: a wireless signal spreads into the air, reaching further than intended and easier to intercept than a wire, so wireless networks lean heavily on encryption.

Clients, Servers, and the Whole Journey

1. A client requests data or services (e.g. a phone loading a page); a server is the powerful computer that stores and provides them.
2. Full journey: a request leaves the client, passes a switch or access point to the router, out through the modem, across the internet to a server, and the reply travels all the way back.
3. One server answers many clients, so popular services run on many machines; too many requests at once overwhelm a server, which is why sites buckle under a surge of visitors.
   1. A failure at any link (dead modem, downed router, overloaded server) breaks the conversation, so knowing the components helps locate a problem.

Components, Infrastructure, and Power

1. Because all of a home's, company's, or country's data flows through a few components, those components are also points of control. Whoever owns the routers, cables, and access points can monitor the flow or cut it off.
2. This concentrates power in ISPs and sometimes governments. A single gateway that everyone's traffic passes through is a chokepoint that can be throttled or switched off entirely.