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ICT (EGT103)
The Internet
What is the internet?
Introduction
The internet is a global network of computers that any computer can join. It is a WAN - which is a series of connected LANs.
Data Transfer
Data packets are sent between computers using protocols that manage how data is sent and received. The internet also uses different models - such as the client-server model and the P2P model - to connect computers in different ways. The internet is leading to more and more people using cloud computing to store files and use web applications online.
Technologies and services available over the internet include:
web pages – HTML documents that present images, sound and text accessed through a web browser
web applications - web software accessed through a browser
Techs & Services
native apps - applications developed for specific devices (such as smartphones) and accessed without the need for a browser
voice calls
file sharing
streaming audio and video
Web browser
A web browser is a piece of software that enables the user to access web pages and web apps on the internet. There are a range of browsers available, and they are usually free to download and install.
Web browser
The internet of things
IoT
The 'internet of things' is the concept of networking lots of devices so that they can collect and transmit data. The idea that any object or living being can be uniquely identified on the internet is central to the concept. By automating the capture of information, greater quantities of it can be stored and processed.
The 'thing' in the
'internet of things'
could include:
sensors monitoring conditions on a farm
the contents of a fridge
an object or person being tracked with an RFID tag
IoT Components
Information gathered from such systems can be used to intelligently respond and adapt to the needs of an environment. For example, if a system detects that a room is empty, lights and heating can be automatically switched off to reduce waste.
Connecting to the Internet
To connect a computer or a device to the internet, you need:
- an ISP
- a modem or router (wired or wireless)
- a web browser or app
- a connection to the network (through a copper wire or a fibre optic cable)
Connecting to the internet
Fibre optic cabling is made from glass that becomes very flexible when it is thin. Light is passed through the cable using a transmitter. Light travels quickly through the light-reflecting internal wall of the cable.
Fiber Optic
Fibre optics
The transmitter in the router sends light pulses representing binary code. When the data is received, it is decoded back to its binary form and the computer displays the message.
Advantages
- the individual cables are thinner, so larger quantities of cable can be joined together compared to copper
- there is less interference than copper
- there is less chance for degeneration
- the UK telephone network still has areas that use copper cable
- replacing copper with fibre optic cabling is expensive
Disadvantages
Copper cable
Copper cable uses electrical signals to pass data between networks. There are three types of copper cable: coaxial, unshielded twisted pair and shielded twisted pair.
Shielded twisted pair (STP)uses copper shielding around the twisted wires to make them less susceptible to interference.
Copper cable
Coaxial degenerates over long distances.
Unshielded twisted pair (UTP) is made by twisting the copper cables around each other and this reduces degeneration.
Advantages
- a cabled telephone can be powered directly from the copper cable, so the phone will still work if there is a loss of power
- copper can be cheaper to set up than fibre optic cabling
Advantages
Disadvantages
- degenerates over long distances
Disadvantages
Broadband connections
The internet is transmitted both on physical wires and wireless connections. Broadband internet is transmitted on physical wires that run underground and under the oceans.
Download speeds tend to be faster than upload speeds.
Broadband connections
Connection Media
ADSL
ADSL (asymmetric digital subscriber line) provides connection speeds of up to 24 Mbps and uses a telephone line to receive and transmit data.
The speed that data can be transferred is dependent on a number of factors:
ADSL
- Signal quality can vary between phone lines and whilst it doesn't affect voice signals, it does affect data transmissions.
- The distance between the modem and the telephone exchange has an effect on the speed at which data is transferred. A distance of 4 km is considered the limit for ADSL technology, beyond which it may not work.
- An ADSL modem or router is needed for broadband internet access over ADSL. This is usually provided by the ISP.
Cable
Cable companies do not use traditional telephone lines to provide broadband internet access. They have their own network which is a combination of co-axial copper cable and fibre optic cable. Copper wires connect a house to the nearest connection point - usually a green cabinet in a nearby road. From there, the cables to the telephone exchange will be fibre optic.
With their purpose-built infrastructure, cable companies are able to provide speeds of up to 200 Mbps - considerably faster than the highest available ADSL speed (24 Mbps).
A cable modem or router is needed for broadband internet access over cable. This is usually provided by the ISP.
Cable
The making and receiving of phone calls is not affected because the telephone line is not used.
3G and 4G
The wireless 3G and 4G networks can be accessed through a smartphone without the need for a WiFi router. The data is transmitted through the cellular phone network rather than the physical cabled network of broadband. This enables anyone to connect to the internet as long as there is a 3G or 4G connection available.
3G allows for up to 6 Mbps to be downloaded and 4G allows for up to 18 Mbps.
3G and 4G
Advantages
Advantages
- it provides an internet connection on the move
- there is the ability to transfer data fairly quickly with 4G
Disadvantages
Disadvantages
- it can be expensive to download data
- some areas don't have 3G or 4G connections
Protocols
The internet is similar to a road network in that it has rules (protocols) that you need to follow and only a certain number of vehicles (data) can get through at a time (bandwidth). If too many vehicles try to go down the same road you get congestion (reduced bandwidth).
Protocols
When two devices send messages to each other it is called handshaking - the client requests access, the server grants it, and the protocols are agreed. Once the handshaking process is complete, the data transfer can begin.
Protocols establish how two computers send and receive a message. Data packets travel between source and destination from one router to the next. The process of exchanging data packets is known as packet switching.
Protocols manage key points about a message
- speed of transmission
- size of the message
- error checking
- deciding if the transmission is
synchronous or asynchronous
Protocols manage key points about a message
TCP/IP
(transmission control protocol/internet protocol)
TCP/IP (also known as the internet protocol suite) is the set of protocols used over the internet. It organises how data packets are communicated and makes sure packets have the following information:
source - which computer the message came from
TCP/IP
destination - where the message should go
packet sequence - the order the message data should be re-assembled
data - the data of the messag
error check - the check to see that the message has been sent correctly
Internet protocols
Within TCP/IP there are several key protocols. These include the following.
- IP Address
- FTP
- HTTP/HTTPS
- SMTP and POP3
- VOIP
Internet Protocols
Did you know?
The 32-bit IP address system is also known as IPv4. It allows for just over 4 billion unique addresses. IPv6 is now coming into use. IPv6 uses 16 bits for each section of the address, creating a 128-bit address. This allows almost 80 octillion unique IP addresses.
IP
Every device on the internet has a unique IP address. The IP address is included in a data packet. IP addresses are either 32-bit or 128-bit numbers. The address is broken down into four 8-bit numbers (each is called an octet). Each octet can represent a number between 0 and 255 and is separated by a full stop, eg 192.168.0.12.
To find your IP address you can use the ipconfig command line tool.
Home and small business routers often incorporate a basic dynamic host configuration protocol (DHCP) server which assigns IP addresses to devices on a network.
IP
FTP
FTP is used to transfer large files. It is often used for organising files on a web server for a website. You can have private access to an area on an FTP server where you can upload your files. You can then give another user access to download the documents that you have shared.
FTP
HTTP/HTTPS
HTTP transfers web pages from web servers to the client. All web page addresses start with http. An https address is a secure web address which has been encrypted. An https address is used for sites holding bank details and secure information.
When adding an authentication layer to HTTP it becomes HTTPS.
HTTP/HTTPS
SMTP and POP3
Email uses these protocols to communicate with mail servers. SMTP is used to send the email; POP is used to receive email. Most email clients allow for transfers of up to 10 MB.
SMTP and POP3
VOIP
VOIP is a set of protocols that enables people to have voice conversations over the internet.
VOIP
Web addresses
Every website address has a URL with an equivalent IP address. A web address contains (running from left to right):
- http(s)
- the domain name - the name of the website
- an area within that website – like a folder or directory
- the web page name – the actual page that you are viewing
Web addresses
Example URL
http://www.bbc.co.uk/nature/life/frog
In this example from BBC Nature:
- http is the protocol
- www.bbc.co.uk is the domain name stored on a DNS
- /nature/life/ is the folder structure leading to where the web page is located
- frog is the requested web page
Example
URL
Name Servers
Name servers are used to host and match website addresses to IP addresses. DNS is the main system over the internet that uses the name server.
Fetching a Web Page
When you type in a URL, the ISP looks up the domain name, finds the matching IP address and sends it back.
The web browser sends a request straight to that IP address for the page or file that you are looking for.
Every website has a URL with an equivalent IP address.
Streaming
Streaming high-quality images, music and video requires a lot of data. Compression reduces file sizes whilst keeping the high quality of the original media.
Streaming
Music and video
Compression is important for reducing music and video file sizes. Music and video files can both be either downloaded as permanent files or streamed temporarily.
A downloaded file creates a file you can store permanently. Streamed files are not stored permanently. Streaming allows data to be used immediately but the whole file is not downloaded. Popular streaming sites include BBC iPlayer, Spotify and YouTube.
Music and video
Data is streamed by the service to the client. The client could be a web application, web browser or native app. A browser needs to use HTML5 or a plug-in to decode the audio or video. HTML5 is a new version of HTML which makes it possible for compatible browsers to stream audio and video without the need for plug-ins.
Buffering
A buffer is a temporary storage space where data can be held and processed. The buffer holds the data that is required to listen to or watch the media. As data for a file is downloaded it is held in the buffer temporarily. As soon as enough data is in the buffer the file will start playing.
Buffering
When you see the warning sign 'buffering' this means that the client is waiting for more data from the server. The buffer will be smaller if the computer is on a faster network.