A collection of web pages stored on computers all over the world, accessed via the Internet, with no central storage or owner
URL (Uniform Resource Locator)

A web address, all of which are unique
Parts of a web address

1. www
2. .abc
3. .co
4. .uk
5. /images/logo.jpg
Domain names

Top Level Domains (TLDs) such as .uk, .fr, .es, .de, .cz, .com, .org, .gov, .edu
HTTP (HyperText Transfer Protocol)

A protocol, a set of rules that web browsers and servers use to exchange information. If everyone follows the same set of rules, everything works.
Data Packets

Data transmitted over the Internet is broken down into smaller chunks or packets to be sent, with the destination and sender's addresses added, and each packet numbered and put in the right order again at the other end
Packet switching

Each knot is a node or router, and packets go the fastest way, not the shortest, which may differ for each packet
Sending images as packets
IP Addressing

Every computer in the world has a separate, unique address, so data can be sent to these addresses to request or display a web page
DNS (Domain Name Server)

A DNS converts a web address or URL into the correct IP address for the computer that the web site sits on, making it easier to remember than the IP address
The three main types of network topologies are bus, star, and ring.
Network topology refers to the physical layout or arrangement of nodes (devices) and connections within a computer network.
Network topology refers to how nodes are arranged within a network
A network is a collection of devices connected by communication links.
The internet is the largest computer network, connecting millions of computers worldwide
Bandwidth

The amount of data that can be carried at a time
Calculating download speed

1. Get file size and speed into same unit
2. Divide file size over speed
Calculating download speed

1 MB file on 8Mbps connection: 1 second
10 MB file on 8Mbps: 10 seconds
700 MB music CD on 8Mbps: 11.66 minutes
700 MB music CD on 2Mbps: 46.66 minutes
Connection Speeds

Measured in Mbps (Megabits per Second)
1 megabit is 10^6 or 1,000,000 bits
Run a speed test: www.speedtest.net
Upload vs Download Speed

Download speeds are faster than upload speeds because most users spend more time downloading than uploading
Broadband

A high-speed connection to the internet that has superseded the use of dial-up connections
Fibre optic glass thread is used in modern cables, with up to 1,000 fibres in a single cable
Potential bandwidth can be many terabytes per second
Buffering

Occurs when a movie or music track plays faster than it downloads
Computer stores some of the file in a buffer until it can begin playing the whole thing
Wireless connectivity

Must be close to a WiFi hotspot or router
Slower than a wired connection
Interference from walls and furniture
Greater security risk
No need to be physically connected
Can connect mobile devices
First cable, 2,500 miles long, was laid across the Atlantic, after many difficulties including storms and cable breakages

1858
For each mile of cable, 133 miles of copper and iron wire was needed
Total weight of the cable was one ton per mile
Advantage of wireless connectivity
There is no need to be physically connected
Purpose of buffering

Temporarily store downloaded data (e.g. a film or music)
Network topology

The arrangement of the elements (links, nodes, etc.) of a communication network
Types of network

LAN (Local Area Network)
WAN (Wide Area Network)
LAN (Local Area Network)

Usually operates on a single site or within a single building
WAN (Wide Area Network)

Cover a large geographical area
Use cables, telephone lines, satellites and radio waves to connect
Used by international organisations
Bus topology

Failure of one node does not affect the rest of the bus network
Star topology

Easy to install and expand with extra nodes
In a ring network

Cable failure anywhere will affect the whole network
In a ring network

Need to 'break' the ring in order to add a new node
All nodes must be switched on in a ring network for the nodes to communicate
Router

Traffic policeman for data packets, sends them on their way in the best direction