# Computing - Structure of the Internet

> Source: https://ollybritton.com/notes/a-level/computing/topics/structure-of-the-internet/ · Updated: 2024-08-25 · Tags: computing, networking

##### What is the largest network in the world called??
The Internet.

##### What is the World Wide Web??
The collection of resources that can be accessed via the Internet.

##### What is main part of the Internet called??
The backbone.

##### What is the backbone??
The set of connections that connect large networks at various points on the globe.

##### If the backbone is at the bottom of the hierarchy of the Internet, what is next??
Regional networks.

##### Who controls regional networks??
ISPs

##### What goes on top of regional networks in the hierarchy of the Internet??
Home networks.

##### What protocol is used to uniquely identify devices on a network??
The Internet Protocol

##### What does an IPv4 address consist of??
$4$ octet values.

##### What is an octet??
Numerical values described by $8$ bits.

##### In an IPv4 address, how many bits are used for each component??
$8$ bits.

##### How many unique addresses do IPv4 provide??
$3.4$ billion.

##### What is the purpose of a URL??
To specify how and where you can access a resource across a network.

##### What are the two components of a URL??
* The protocol
* The domain name

##### What does URL stand for??
Uniform Resource Locator

##### What is the purpose of DNS??
To convert domain names to their IP addresses.

##### ![PHOTO DNS MISSING ROOT](paste-35f570baa663eab7e12978878cec06050b72cea0.jpg) What is missing??
`root`

##### ![PHOTO DNS MISSING GENERIC TLD](paste-b6b3c7a2625de11301af710015d5e9810ebf42ca.jpg) What is missing??
Generic TLDs

##### ![PHOTO DNS MISSING COUNTRY TLD](paste-4477ba0b53275ac728d3074feeb8ebfd243b58fd.jpg) What is missing??
Country TLDs

##### ![PHOTO DNS MISSING 2LD](paste-cd41e96ee5263bc15708517801c6eb79cd6a6f20.jpg) What is missing??
2LDs

##### ![PHOTO DNS MISSING 3LD](paste-663300f8ecb0d58a7e30311fdce12529e5f5cecb.jpg) What is missing??
3LDs

##### Who controls which domain names are allocated to which IP addresses??
Internet Registries

##### What do internet registries work together to maintain??
A database of domain names and their corresponding addresses.

##### If a client has no cached record of an IP address for "www.google.co.uk", what will it do??
Sends a query for that domaint to a DNS server.

##### If a DNS server knows about a certain domain name, what two things can it respond with??
* An error saying it's not found
* The IP address

##### If a DNS server doesn't know about a certain domain name, what does it response with??
A referal to a lower-level DNS server.

### 2021-02-11
##### In "https://www.google.co.uk/search", what is "www.google.co.uk" called??
The fully-qualified domain name.

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