1. Topic 5: Communication and the Internet

2. Communication and the Internet: The Internet
What is the Internet?
It’s safe to say that communication, and the way we communicate, has come a long way the past few decades
Where we originally had to physically travel (or send messages) to communicate over vast distances
Now we can send a message that arrives almost instantly
We also have access to vast sources of information, education, and entertainment
How can we do all this?
Communication and the Internet: The Internet

3. Communication and the Internet: The Internet
What is the Internet?
This is all because of The Internet
We know that a LAN is a connection of multiple devices together
Over a relatively small area
A WAN is the same, except over greater distances
The Internet is a WAN that connects millions of LANs together
All over the world
Communication and the Internet: The Internet

4. Communication and the Internet: The Internet
What is the Internet?
As the Internet reaches across the entire globe
It allows us to communicate with any device
Even over different countries/continents
It is a vast web of communication
However, how does it all work?
How can we communicate with a device in a different country?
Communication and the Internet: The Internet

5. Communication and the Internet: The Internet
Addresses
First, it’s important to understand one very important feature of any network (LAN or WAN)
Every device has an address
Addresses, like in the world, should be unique for every device
They exist to help network managers (the backbones of LANs and WANs) work out where to send data
Such as: If we search for “Cute kitten photos”, where should that request be sent?
Communication and the Internet: The Internet

6. Communication and the Internet: The Internet
Addresses
These addresses are known as IP (Internet Protocol) addresses
Used in the TCP/IP stack (which we saw before)
Each address is a series of binary digits
Usually shown in decimal, with dots separating each major component
For example, this is an IP address
Communication and the Internet: The Internet

7. Communication and the Internet: The Internet
Addresses
Each component in this address can have a maximum value of 255
Making each component 1-byte long
Devices will use these addresses to work out where to send any relevant data
The Internet will also uses these addresses to work out which LAN to send data to
We’ll see more on this later
Communication and the Internet: The Internet

8. Communication and the Internet: The Internet
Routers
Let’s move on to the smallest part of the Internet
The LANs that are connected together
LANs, in this case, are made up of the devices and a router
The devices can by anything from computers to mobile devices
The router, however, is a bit more special
Communication and the Internet: The Internet

9. Communication and the Internet: The Internet
Routers
A router is a small-ish device that acts as the backbone of a LAN
Typically, all other devices on the LAN connect to it
It is this router that gets connected to all other routers on the Internet
Each router keeps track of any outbound and inbound information
In the form of packets
Based on the address information in these packets, it forwards (or routes) them to different devices
Thus the name router
Communication and the Internet: The Internet

10. Communication and the Internet: The Internet
Routers
Each packet of data contains information such as
What protocol is being used (like HTTP or FTP)
The data that is being sent
The address to send the data to
This address will be the IP address we mentioned earlier
The router will look at the IP address of the destination
Then forward the packet to the device with that IP address
Communication and the Internet: The Internet

11. Routers Over the Internet, we connect these routers together
Forming something like a router tree
The individual LANs are at the very bottom of the tree
Homes, businesses, schools, etc.
They will all be connected together using another router
This process repeats until we have all routers connected together
Router
International
National
Regional
Local
Networks in companies, schools, colleges, etc.
Communication and the Internet: The Internet

12. Routers
Each router on a LAN will have its own IP address (known as a public IP address)
This IP address will be given to it by a company
More on that in a little bit
However, unique 4-byte numbers are finite
To easy the number of IP addresses used, we differentiate between public and private IP addresses
Router
International
National
Regional
Local
Networks in companies, schools, colleges, etc.
Communication and the Internet: The Internet

13. Communication and the Internet: The Internet
The IP Address Problem
To give some context here, the Internet originally had multiple devices connect to all other devices
Instead of using a router
IP addressing was still a thing
However, due to the extremely large number of devices that could potentially connect
We would run out of IP addresses!
Communication and the Internet: The Internet

14. Communication and the Internet: The Internet
The IP Address Problem
To get around this, IP addresses were separated into two
One group for public IP addresses
One group for private IP addresses
Public IP addresses are the ones that routers use to communicate over the Internet
This is the address we see when searching for our IP address online
Communication and the Internet: The Internet

15. Communication and the Internet: The Internet
The IP Address Problem
Private IP addresses are handed out by a router (or similar device) to devices
Any device that connects to it on a LAN
These addresses typically start with
Each LAN will have its own set of private IP addresses
Need to be unique within the LAN
But different LANs can use the same private IP addresses
Communication and the Internet: The Internet

16. Communication and the Internet: The Internet
The IP Address Problem
However, even with this difference between public and private IP addresses, we still have a problem
We are running out of public IP addresses
The current version of IP address, IPv4, is the one that uses 4-bytes for its addresses
The version we’re slowly shifting over to is IPv6
Which has 16-bytes for every address
Communication and the Internet: The Internet

17. The IP Address Problem IPv6 addresses now have 8 components to them
With each component having 2 bytes of information
IPv6 addresses are also shown in hexadecimal (not decimal)
As it makes the address string smaller
IPv6 addresses always have 16 bytes of information (even if fewer are shown).
That’s because we assume that the remaining components of the address are all 0
So the example on the right is actually:
aabb:ccdd:eeff:0011:0000:0000:0000:0000
aabb:ccdd:eeff:0011
Communication and the Internet: The Internet

18. Communication and the Internet: The Internet
The IP Address Problem
By moving over to an address with more available bytes, we’re allowing more unique addresses
Which solves the ‘crisis’ of not having enough addresses for all the LANs connecting to the Internet
However, routers, servers, and other devices need to adopt this change in address
And not all have yet
Which they will need to do at some point
Communication and the Internet: The Internet

19. Internet Service Providers
Each LAN needs to be connected to the Internet somehow
Done through Local, Regional, and higher-up routers
For this to work, cables (or other mediums) need to be set up to connect the LAN
A lot of cable infrastructure is already in place
Once in place, a company then leases lines from a network they manage
These companies are called Internet Service Providers (ISPs)
Communication and the Internet: The Internet

20. Internet Service Providers
ISPs are given public IP addresses that they can lease to customers
When a customer signs up, they assign an available IP address to them
This lets the customer access all other LANs on the Internet
Including web servers and other services
Communication and the Internet: The Internet

21. Domain Name Service (DNS)
An initial problem with IP addresses is that any communication required them
Not an initial problem (as there were a small number of them).
However, became more of a problem as more IP addresses were added
Made communicating between computers more ‘complex’
Thus the Domain Name System (DNS) was created
Invented for users to identify
Networks
Network hosts
Use of a memorable name reference
Communication and the Internet: The Internet

22. Domain Name Service (DNS)
Domain names consist of the following:
A root (the top-most directory in the hierarchy)
The network domain or website
A domain
Observe the root hierarchy (i.e. include it)
Examples: funtech.co.uk, rbwm.gov.uk
Each domain identifies a network of computers located at that location
A host address
The first section of the domain (most-significant)
Examples: mail.google.com
Communication and the Internet: The Internet

23. Domain Name Service (DNS)
Routers need some way of converting between domain names and IP addresses
As the IP address is the actual address
The domain name is just a representation of it
This is where DNS servers come in
They help translate domain names into IP Addresses
Most routers (whether local or regional) have DNS servers running
Communication and the Internet: The Internet

24. Communication and the Internet: The Internet
The World Wide Web
All of these ISPs, IP Addresses, Domain Names, LANs, and WANs come together to form the Internet
Note that the Internet is only the network itself
However, we often hear of another term
The World Wide Web
These are not the same things
The Internet is the network itself
The World Wide Web is hosted on the Internet
Communication and the Internet: The Internet

25. Communication and the Internet: The Internet
The World Wide Web
The World Wide Web is a series of interconnected webpages
A type of document that can be rendered via web browsers
Each webpage is created using HTML (Hyper-Text Markup Language)
A scripting language that is interpreted by a web browser
Formed of entities and attributes
<html>
<head>
<title>Hello World</title>
</head>
<body>
<h1 style=“font-size:2em;”>Hello World</h1>
</body>
</html>
Communication and the Internet: The Internet

26. Communication and the Internet: The Internet
The World Wide Web
These webpages will be hosted on web servers
Servers that allow clients to request HTML files
Usually via HTTP or HTTPS
These web servers need to be publicly accessible, which means they need a public IP address
Rather than getting users to browse these web servers using IP addresses
They let users find them via domain names
These domain names are entered in a web browser
Contained in something called a URL
Communication and the Internet: The Internet

27. Communication and the Internet: The Internet
The World Wide Web
URL stands for Uniform Resource Locator
It displays information on
The protocol the request is using
The domain name of the web server to access
Which file to request
Here is an example:
Protocol Domain Folders/File
Communication and the Internet: The Internet

28. Communication and the Internet: The Internet
The World Wide Web
When a web browser (the application we use to view the web) requests a webpage
Using the URL we enter in the address bar
It sends a HTTP/HTTPS request to that web server
Containing information like our address, what we’re requesting, and more
When the browser receives a response (in HTML form), it renders that HTML on the application’s window
Communication and the Internet: The Internet

29. Communication and the Internet: The Internet
Other Network Devices
Although the router is arguably the most important device on a network for connecting to the Internet
It’s not the only device for that
In fact, routers don’t work without a modem
A modem will translate electrical signals coming from the leased network cables
Into a form that the router can understand
This translation is both ways
Translates electrical signals coming into and out of the LAN
Although sometimes found on their own, most routers come with a built-in modem these days
Communication and the Internet: The Internet

30. Communication and the Internet: The Internet
Other Network Devices
While a modem and router is required for connecting/talking to the Internet
We may need other devices for managing/connecting devices internally on the LAN
One such device that can help with that is a switch
Switches help connect multiple physically- connected devices to a single cable
The single cable usually leads to a router
Each device needs its own physical cable to connect to the switch
Communication and the Internet: The Internet

31. Communication and the Internet: The Internet
Other Network Devices
We tend to find switches in areas with lots of physically-connected devices
Like a school or business
Switches are designed to switch electrical signals to the correct device
Most large switches are long, cuboidal devices
However, the router also acts as a switch
As it can also connect multiple devices together at once
Communication and the Internet: The Internet

32. Communication and the Internet: The Internet
Other Network Devices
If we want to connect multiple devices wirelessly, we can use a Wireless Access Point (WAP)
These perform the same function as Switches
Except using radio waves instead of electrical signals
Also like Switches, most routers have wireless functionality built into them
Except WAPs can extend the range of a wireless signal
Communication and the Internet: The Internet