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In this lesson we will…
• Examine the difference between the Internet, the Web and the Intranet.
• Cover packet switching and how the Internet enables the Web.
Starter Activity
What do you do online?
OMG
How would you feel if you couldn’t do any of this?
How would you cope?
Internet
Web
Intranet The Internet houses the Web but why does the intranet overlap both?
How do these intercept? What are their functions?
The Internet, the Web and the Intranet
The Internet • This is a global system of networks which are connected
together using a particular protocol called the TCP/IP . This is a procedure which controls how computers send information to each other. One important feature of this system is its decentralised structure. Because there is no central point on which communications depend, the system can continue to function well even when some connections break down.
The World Wide Web • This application, which was created in 1989, sits on top of the
Internet. It contains information resources in many forms (documents written in HTML, images, music, video, etc.) which can be linked together. Users can access information via a browser (which helps them find information, entertainment or services), or navigate between documents by clicking on hyperlinks.
• Each information resource has a unique URL and these resources
can be transferred using another protocol called HTTP.
Intranet • Many companies want to take advantage of the
networking capabilities of computers, but also need to keep their information restricted and secure. For this reason they often use a internal network to help them communicate, share information, provide computing services, or create internal websites. Employees of organisations can access the information in these systems, but external access is controlled or blocked.
Communication and the Internet…
• Protocols: Set of rules for communication
• Transmission Control Protocol (TCP) and Internet Protocol (IP): Protocols for communicating across the Internet
TCP and IP
• TCP: underlying layer of the Internet ensuring delivery of information
• IP: Responsible for providing addresses for sending information
IP Packets
• Items that are transferred across the networks• IP Packet:
HeaderActual Data
• Source IP Address, • Destination IP Address, • Packet Number, • Number of packets that make up
that item
• Foundations of communicating across the Internet:– Protocol are a set of rules– TCP: delivering the information– IP: Providing the addresses– Information is broken into IP Packets
Questions?
So far…
Digital Post Office
• Write the Letter• Sign the Letter• Put it in an envelope• Write the Address of Destination on Envelope• Place a Stamp on the Envelope• Place Letter in Post Box• Local Post Man picks up letter amongst others from post
box• Letter goes through Sorting Office• New local Post Man delivers letter to destination
Activity 2
Together, organise the slips which represent the steps for packet switching into the correct order – think about the post office analogy to help you
Packet Time To Leave (TTL)
• Data packets have TTL number • TTL is number of server-to-server hops before
the packet is no longer forwarded (hop limit).• A server receiving a packet reduces TTL by 1
before passing it on.• A server receiving a packet with TTL discards it
and sends a re-send message to the originating server (i.e. send packet again)
Point A
Point B
HE LL O
10
9
8
7
6
9
9
5 4 3 2 1
8
7 6 5
4
3
8 7 6 5
4
3
2
1
Packet Switching
0Request new packet
9
8
7 6 5 4
3
10
IP Address
• A unique label assigned to each device in a computer network that uses the Internet Protocol.
• Does anyone know what is the most common form of IP Address and what is the newer IP Address?
IPv4
• Most common Internet Protocol• Limited number of IP addresses• IPv6 – newer version (to be discussed at a
later date)
IP Addresses
0 to 255 0 to 255 0 to 255 0 to 255
192 192 158 1581 chunk
1 byte1 chunk1 byte
1 chunk1 byte
1 chunk1 byte
IP Addresses
Are these IP addresses on the same network?
1) 126.203.123.123 and 126.203.100.100
2) 126.203.123.123 and 123.123.126.203
3) 126.203.97.54 and 126.203.123.123
IP Addresses
Are these IP addresses on the same network?
1) 126.203.123.123 and 126.203.100.100 - YES
2) 126.203.123.123 and 123.123.126.203 - NO
3) 126.203.97.54 and 126.203.123.123 - YES
Summarise…
• Can you individually write 4 or 5 points that you have learnt and can take away with you today…
• Internet is the foundation• Web uses the Internet• Intranets are private networks• Communicating across the Internet:– Protocol are a set of rules– TCP: delivering the information– IP: Providing the addresses– Information is broken into IP Packets
• Methodology used for communicating IP Packets across the Internet is called Packet Switching
To Summarise…
To Summarise…
• IP Addresses are used to identify a device on a network
• IPv4 is most commonly used IP Address• IP Addresses are made up of 4 chunks, 32-bits– First 2 Chunks = Network Identifier– Second 2 Chunks = Host Identifier
*Key Terms Handout
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