The Structure of the Internet

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? 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

Activity 1 Now we are going to fill in the gaps …

The Internet… The Resilience of the Internet

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…

Now to get your brains working that little bit more….

Post Office Analogy When you send a Letter in the Post what is the process…

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 Switch Networks - 1 Moving a File from A to B

Packet Switching Point A Point B

Now Lets Give it a Go….

Packet Switching Point A Point B

Packet Switch Networks - 2 Routing around missing servers

Packet Switching Point A Point B

Packet Switch Networks - 3 Packet order

Packet Switching Point A Point B HE LL O

Packet Switch Networks - 4 Time-To-Live (TTL)

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 LLO Packet Switching 0 Request new packet

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)

IPv4 32-bits (4 bytes) = 2^32 different values (this is binary which will cover at a later date)

Bits/Bytes If 32 bits = 4 bytes, so how many bits are there in 1 byte?

Fun Fact… Half a Byte (4 bits) is called a Nibble!

IP Addresses 0 to chunk 1 byte 1 chunk 1 byte 1 chunk 1 byte 1 chunk 1 byte

IP Addresses Network IdentifierHost Identifier

IP Addresses Are these IP addresses on the same network? 1) and ) and ) and

IP Addresses Are these IP addresses on the same network? 1) and YES 2) and NO 3) and 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…

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

Any Questions?