CS51 : The grid

It's OK connecting computers together in a local environment, but it's much more fun (and potentially quite dangerous) communicating with other computers around the globe. But how does that even work?

We are learning ...
  • About the ways in which data is transferred across a global network
So that we can ...
  • Describe the physical structure of the Internet
    - Cable infrastructure
    - Routers / switches
  • Describe methods of data transfer
    - Circuit switching
    - Packet switching
    - The role of IP Addresses
    - The role of Internet Registrars
    - Uniform Resource Locator (URL)
    - The Domain Name System and the use of domain names

Activity 1 The Physical Structure of the Internet 

The Internet (with a capital 'I') is defined as 'A publicly accessible network of networks'. The term internet (with a lower case 'i') literally derives from inter (between) and net (network) and can be used to describe any group of networks whether public or private.

Early attempts to link computers together were driven by the need to share resources between powerful mainframe computers and terminals in research institutes. The Internet, as we know it, began life in the late 1960s as ARPANET, part of an effort to connect together American military computer systems in the United States of America as a secure way of transferring sensitive data during the Cold War. ARPANET was the first network to implement the TCP/IP Protocol.

During the 1980s, the network was expanded to include universities and research centres. The Internet uses a globally unique address space of IP Addresses based on TCP/IP (Transmission Control Protocol / Internet Protocol) to allow public access to services like web pages.

Yes, the structure of the Internet today is extremely complicated. The physical components of the Internet are owned by many hundreds of companies, some of whom have resources all over the world. For the purposes of routing traffic from one place to another, however, the Internet is divided into physical Autonomous Systems, each allocated an Autonomous System Number (ASN). AS Numbers are assigned in blocks by the Internet Assigned Numbers Authority (IANA) to the five Regional Internet Registries (RIR) who manage allocation to organisations in their regions. We'll explore the RIRs in more detail later in this topic.

Click to enlarge (Source)

As of May 2017, the three biggest companies (full list) who manage the physical Internet infrastructure are ...
These, along with the hundreds of other companies involved, provide the backbone of the Internet.

If you really want one, have a look here ...

Task 1.1
Submarine Cable Map

Stage One

Make some notes on this section, paying particular attention to the words in bold.

Stage Two

It may surprise you to learn that there are over half a million miles of network infrastructure cable under the sea. The Submarine Cable Map website charts all the currently known undersea cables.

Click the visit the Submarine Cable Map website

Visit the website and investigate some of the cables. 

Stage Three

You also might want to buy a book by Andrew Blum called Tubes : Behind the Scenes at the Internet. It explains how the Internet is structured and 'where' it is.

OUTCOME : Notes on the structure of the Internet

Circuit switching

In the infancy of analogue communication, clients were connected to other clients using circuit switching in a telephone exchange.

In a circuit switched network, physical connections were made between nodes in a network either by a human (telephone operator), mechanically, or more recently, electronically. 

Telephone Operator - an early 'switch' (1:32)

Circuit switching is a connection-oriented service where the 'caller' must first establish a physical connection to the 'callee' before any communication can begin. This is a time consuming and resource heavy operation involving routing the 'call' to a locally available node or switch allocating network resources as required. These resources could be frequency bands in Frequency Division Multiplexing (FDM) or time slots in Time Division Multiplexing (TDM) schemes. The connection stays active during the duration of the communication, even if the connection is idle.

A stylised circuit switched network. The dotted lines show potential connections.

In a circuit switched network various technologies are used to minimise the connection time and handle network interruptions, therefore, they are still useful in situations where a long lasting connection is required. Don't get confused with virtual circuits - these are packet switched networks which emulate circuit switched networks.

Task 1.2
 Circuit switching history lesson

I've started a YouTube playlist of various historic videos about early telephone exchange technology including the development of the PSTN (Public Switched Telephone Network). Watch the videos, no need to take notes, just be aware of the change from manual exchanges to electronic exchanges and how circuit switching technology is still used today at the ends of your phone connections.

Click to view the playlist on YouTube

OUTCOME : No specific outcome.

Yes, but even though circuits switched networks have these advantages (high capacity, reliability, quality of service, simple user control), they also suffer from some serious disadvantages as well ...
  • State maintenance : the circuits require monitoring to ensure that they are still operating and reactive maintenance should there be a problem or breakdown in the circuit (such as re-routing).
  • Establishment overhead : Before any circuit is established, the optimal route from sender to receiver must be established. This 'handshaking' operation can take time.
  • Wasted capacity : If a certain frequency or timeslot is occupied by a circuit which is not currently in use, it is unavailable for use by any other circuit thereby wasting capacity.
  • Blocking : If there are no available circuits, the sender must wait until a circuit is free.
Whilst there is no real choice for voice communication (other than VOIP), data transfer does not require this dedicated line approach since, it doesn't really matter what order the data arrives at the destination as long as it's put back into order before it's delivered to the receiver. In the mid 1960s, computer scientists in America (Kleinrock and Baran) and the UK (Davies) began development of a packet switched network later to become the basis for the ARPANET.

Packet Switching

In a packet switched network, there is no need to establish a circuit before transmission begins. Packet switching is a connectionless service.

OK, OK, there are always exceptions to the rules.

The data is broken up into small chunks called packets before 'hopping' between special switches, called routers. The routers use dynamic routing algorithms to send the packets on the next step depending on the network load. 

Click to enlarge

Apart from the actual data (the important stuff), the packets also contain lots of other information which enable them to make their way towards their destination and be reassembled correctly when they get there. These 'headers' are added by software on the sending computer as the packet is prepared for transmission and stripped off when the packet is received.

Click to enlarge (and print for your folders)

Yes, OK, this looks a little complicated doesn't it? I've tried to give you the essence of the structure of these little 'boxes' that are travelling around the Internet.

Points to note ...
  • The frame is constructed and deconstructed in the TCP/IP software stack (which we'll learn about in the next topic that we study).
  • It's called a 'frame' because it surrounds the IP datagram.
  • The IP datagram is often known as an IP packet.
  • As I mentioned in the diagram, TCP (Transmission Control Protocol) is a connection-oriented service which guarantees safe delivery of its packets. TCP is used for transmission of data which we require to be complete such as documents, binary files, archives etc. The alternative, UDP (User Datagram Protocol) does not deal with 'lost' packets and is used mainly for video and audio transmission.

Task 1.3
 The Warriors of the Internet

It's the blockbuster you've been waiting for - the Internet as you've never seen it before. Yes, it's the world famous and widely watched 'Warriors of the Net'. Supported by a cast of millions, come with us as we journey into 'the Net'.

Warriors of the Net HD (12:59)

Now, using the diagram of the structure of the Ethernet frame and what you have learnt by watching the video, write a story called 'A day in the life of an Internet packet'. I would also like you to come up with 5 extra questions you would like to know the answer to so you can quiz your teacher at the end of the lesson. If your teacher can answer the questions, you can leave early!

OUTCOME : A story about a day in the life of an Ethernet packet and an early lunch!


Packets are routed across the global Internet using a combination of their destination IP address and their hardware MAC addresses. Packets will only be routed outside their local network if the destination IP address is considered not to be part of the local network. The host / router knows, through use of routing tables, where the packets should be sent. If the local host / router does not know of the destination for a packet, it sends the packet to the default gateway which passes the packet onto the next router in the network.

All this might seem a little confusing, so there are a number of ways in which you can 'see' the route that the packets are taking across the Internet. For instance, if we want to trace the route taken from our computer to google.co.uk, here are three ways we could achieve this ...
  • Using the Windows 'tracert google.co.uk' command


  • Using a free piece of software called eToolz from www.gaijin.at

  • Using a free piece of software called 'Open Visual Traceroute' from visualtraceroute.net

Task 1.4
 Where on Earth ... ?

Use any of the three tools to trace the route from where you are now to the following websites ...
  • stackoverflow.net
  • amazon.co.uk
  • github.com
  • ebay.co.uk
  • samsung.com
You might find that some of the traceroute operations take a long time and can timeout. Be patient and if you can't get these to work, have a go at some of your own. Look carefully at the route the requests take across the globe. Sometimes it's amazing how far they physically travel!

Take a screenshot of the results of one of the traces (if you can get one working) and stick this into your notebooks / folders as proof that you've had a go :)

OUTCOME : Awareness of the route which traffic can take across the globe.

Finally, the diagram shows the relationship between some of the routers you might have seen in the trace operations. Hierarchically, the closest router to your computer is likely to be a 'Residential / SOHO (Small Office / Home Office) routers'. Next in the line are your Internet Service Providers (ISP) 'Edge' routers (which you can see named in the traces) which connect their equipment to the 'Core Routers' on the Internet Backbone. The core routers are insane!

Click to enlarge (and print yourself a copy if you want)

Activity 2 Addressing the Internet 

When I showed you the Ethernet frame structure, I mentioned the use of Internet Protocol (IP) addresses and Media Access Control (MAC) addresses and their role in controlling the destination / routing of packets. We've seen list of IP addresses in the 'traceroute' results from the previous task but, what actually are they?

Don't panic!

IP Addresses

Every device connected to the public Internet needs an identifier. IP (Internet Protocol) addresses are numerical addresses which are used to uniquely identify every piece of hardware within the global address space of the system. Internet Protocol addresses come in two flavours - IPv4 and IPv6 (the 'v' stands for 'version').

An example of an IPv4 address

The IPv4 address is normally written in dotted decimal notation where each octet is represented by a decimal number between 0 and 255 (although some values are restricted - see later). IPv4 provides 232 individual addresses within the address space or 4,294,967,296 unique addresses. In IPv4, we can miss out leading zeros from the decimal octet value if we need to, so, we would write instead of (obviously).


An example of an IPv6 address. I've split the binary version onto two lines 'cause it wouldn't fit!

An IPv6 address has a very different format. There are 128 bits grouped in 16s and written as hexadecimal. So, there are 2128 or 340,282,366,920,938,463,463,374,607,431,768,211,456 IPv6 addresses (so we'll never run out, nanobot). You'll notice in this particular address, there are lots of zeros. There are two alternative ways we can write this address, either suppressing leading zeros and writing it as fe80:0:0:0:f026:992e:167b:39ad or by compressing them and writing it as fe80::f026:992e:167b:39ad (which is OK as long as we only do it once per IPv6 address).

The IP addresses of my local Ethernet port

So here is a screenshot of the IP address allocation on the Ethernet adapter in my laptop. Notice that IPv4 and IPv6 addresses as you would expect. The IPv6 address is followed by '%13' which is simply an identifier for the adapter (scope ID) on Windows machines (on a Linux machine, it would be %eth0 or similar) which is required because multiple adapters can have the same type of IPv6 address and this helps with routing.

Task 2.1
 Your IP Addresses

View the IP address allocation for your network adapter on your laptop or desktop.
  1. Click the 'Start' button.
  2. In the 'Run' textbox, type 'cmd' and press the  ENTER  key.
  3. At the prompt, type 'ipconfig' and press the  ENTER  key.
  4. Look for 'Ethernet adapter' or 'Wireless LAN adapter'
Write down your full IPv4 and IPv6 addresses (if present) in your notebook.

OUTCOME : IPv4 and IPv6 addresses from your computer.


All IP addresses are split into two parts - a network identifier and a host / interface identifier. Device IP addresses with the same network identifier are said to be on the same subnetwork or subnet which is useful for administration and routing purposes. IPv4 addresses use a subnet mask or CIDR (Classless Inter-Domain Routing) notation to identify which part of the IP address is the network ID and which part is the host / interface ID.

IP Address  : 11000000.10101000.00000001.11001111 (
Subnet Mask : 11111111.11111111.11111111.00000000 ( (N.N.N.H)
Network ID  : 11000000.10101000.00000001.00000000 (   (N.N.N.0)
Host ID     : 00000000.00000000.00000000.11001111 (     (0.0.0.H)

The '1' in the network mask indicates which bit in the IP address are to be treated as the network ID. A '0' in the subnet mask indicate which bits are treated as the host / interface ID. In practice, we perform a bitwise AND operation on the IP address using the subnet mask to give the network ID. 

Alternatively, you can write the IP address in CIDR notation as which tells you that the left most 24 bits form the Network ID and the remaining 8 bits represent the host / interface ID. Since the introduction of CIDR in 1993, the network mask must be contiguous. CIDR prefixes can range anywhere between 

The length of the host ID part of the IP address determines how many hosts / interfaces are available on the network. For instance, for my home network ...

First host : 11000000.10101000.00000001.00000000 (
Last host  : 11000000.10101000.00000001.11111111 (

Actually, host 0 and host 255 are not allowed so that leaves us with 254 available hosts / interfaces.

Task 2.2
 Network classes and subnetting

Firstly, download the Old fashioned classful subnetting infosheet and print it out for your folders. Read through it with your teacher before you attempt this task.

STAGE ONE : Read this!

In the early days of IPv4, there were five classes of network, A, B, C, D and E into which all IP addresses were segmented. The leftmost bits in the IP address determined to which network class a particular IP address belongs (see Infosheet) and consequently which network mask to apply to determine the Network ID and the Host ID.
  • Default Class A network mask :
  • Default Class B network mask :
  • Default Class C network mask :

As you can see, the IP address for my Ethernet adapter is a Class C address (starts with binary 110) and is therefore assigned a default classful network mask of Hardware still uses these concepts today so it's important that we understand them. However, this scheme caused problems with administration, Internet routing and availability of IP addresses.

With classless subnetting (introduced in 1993), you define the length of the network mask explicitly using 'slash' notation (called a class prefix) as a Variable Length Subnet Mask (VLSM). For instance, a classful class A IP address / could be represented as as a classless address indicating that the leftmost 8 bits of the IP address represent the network ID. You are free to increase or decrease the number of mask bits but if you reduce the default mask length on a publicly routable network, you are asking for trouble!

STAGE TWO : Answer these!

For each of the following classless IP addresses, state ...
  1. The number of bits in the subnet mask
  2. The network ID
  3. The range of host IDs
  4. The number of potential hosts on the network (exclude 0 and 255 from each octet)
You may want to use this fab IP Calculator Tool to help you but you'll have to figure out how to use if first! For a fun little extension task, you can try looking up the IP address portion (i.e. without the CIDR prefix) on ipinfo.io to see who is the registered keeper.
  •    (ipinfo)
  •     (ipinfo)
  •     (ipinfo)
  •   (ipinfo)
  •   (ipinfo)
  •  (ipinfo)
I'd like to see that you understand what these numbers mean. That will involve you either a) writing lots about each IP address and / or b) talking to your teacher about what you have found out.

EXTENSION : If you compare the actual IP addresses I've given you with the old fashioned classes and look at the subnet masks you have derived from the CIDR prefix, you will see that they bare little resemblance to the default classful subnet masks that you would have got had you used to old fashioned method. Interesting, eh?

STAGE THREE : The real world!

The screenshot below shows the IP address allocation for my Internet Service Provider, Internet Central.

Click image to visit Internet Central page at ipinfo.io

As you can see, Internet Central has been assigned just over 17,000 IPv4 addresses. Your task is to prove how the values in the 'Num IPs' column has been arrived at and state the range of IP addressed available in each block. You'll also see that Internet Central have some IPv6 addresses as well - in fact, it appears as though they have a /29 address which gives them management rights to 34,359,738,368 subnets each with 18,446,744,073,709,551,616 IPv6 addresses! In fact, that's such an unbelievably crazily large number, that I might have to give them a ring to check that that is correct ... Watch this space!

OUTCOME : Clear demonstration of understanding of IPv4 subnets.

Good question, but not entirely on the specification so this is extension work. In IPv6, there is no concept of network classes, merely scopes which identify the type of address and fixed portions of the address that represent the global network identifier and the private network identifier. There are always 64 bits available for the host identifier.

Click to enlarge

Some IPv6 address prefixes are reserved for special purposes ...
  • 2001:db8::/32  is reserved for documentation
  • 2002::/16      is reserved for special IPv6 to IPv4 routing prefix
  • fd00::/8       is reserved for local unicast (private) addresses
  • fe80::/10      is reserved for local addresses (like my Link-local IPv6 address)
  • ff00::/8       is reserved for multicast addresses
All other IPv6 addresses starting with 2 (0010) or 3 (0011) are unique global unicast addresses (i.e. public ones).

No, probably not ... yet.

Public and Private IP Addresses

There are certain IPv4 addresses that are reserved and never publicly issued. These are called non-routable IP addresses and form a private address space (as opposed to a public address space) for use internally in private networks. You'll probably find that you have a 192.168.x.x or a 172.16.x.x network at home or in school.
  • - (10/8)            ... 16,777,216 host IDs (the '24-bit' block)
  • - (172.16/12)     ... 1,048,576 host IDs (the '20-bit' block)
  • - (192.168/16)  ... 65,536 host IDs (the '16-bit' block)
  •                                   ... Loopback address (this machine)
Also, any IP address where the host ID is 0 or 255 is reserved and not available for use either. Routers flatly refuse to route requests to these addresses outside their local network. In other words, if I try to send a packet to, a router will never route the packet onto the public Internet. This behaviour reserves IP addresses in these ranges for use internally in as many locations as are necessary.

Task 2.3
 Non-routable IP addresses

Using the resources provided, explain the meaning of the term non-routable address in your own words. 

OUTCOME : Definition of non-routable IP address

What's the point?

What seems like a long time ago, I mentioned routing as a method for passing a packet through a network towards it's ultimate destination. Routing only occurs if the packet needs to pass out of the local network and the router is responsible for forwarding the packet in that instance.

Task 2.4
 IP Address Calculator

Download the IP Address Calculator spreadsheet and save it in a suitable place in your documents. When you open the spreadsheet, you will have to accept the macro security warning or else the sheet won't work correctly.

Unfortunately, the spreadsheet is based on classful subnetting of IPv4 networks so it's not entirely appropriate but it should help you to learn how and when routing will be required. Try the following settings and state whether routing is required or not (look at the sheet) and, more importantly, explain why ...
  • Class A / 0 Subnets / Source : / Destination :
  • Class B / 0 Subnets / Source : / Destination :
  • Class C / 0 Subnets / Source : / Destination :
  • Class C / 4 Subnets / Source : / Destination :
  • Class C / 8 Subnets / Source : / Destination :


OUTCOME : To route or not to route.

The end-to-end principle

The end-to-end principle basically pushes the ultimate responsibility for packet delivery out to the edges of the Internet. The Internet itself runs on the IP protocol which provides unreliable packet delivery (i.e. doesn't care) whereas the machines communicating at the edge of the Internet run the TCP protocol, a connection-oriented, guaranteed delivery service.

What is the end to end principle? (4:50)

So, the end-to-end principle ...
  • means the responsibility for packet delivery lies with the edges of the Internet
  • keeps in the core Internet simple and fast
  • allows innovation to happen at the edges without changing the core

The end-to-end principle

Task 2.5 Net neutrality

The end-to-end principle is sometimes seen as the direct precursor to net neutrality, the principle that the Internet infrastructure should transport packets without bias, treating all data equality. Here are a few useful links which you should read carefully ...
In your notebooks : Write a paragraph explaining the concept of net neutrality using the end-to-end principle in your answer. You should try to avoid bias in your response (difficult since this is a very emotive issue). Write no more than 250 words.

OUTCOME : 250 words on net neutrality

Activity 3 Internet Registrars 

All this talk of IP addresses and no one seems to have explained where they come from? Since the Internet is publicly accessible, it makes sense that the allocation of IP addresses should be centrally managed, and indeed it is. The boss is called IANA or the Internet Assigned Numbers Authority. Underneath that lie five Regional Internet Registries (RIR) who work under the supervisory umbrella of the Number Resources Organisation (NRO).


Until October 2016, IANA was managed under the stewardship of the Internet Corporation for Assigned Names and Numbers (ICANN). All the RIRs serve 'members' or Local Internet Registries (LIR). Two of the RIRs have special members called National Internet Registries (NIR) for management of IP address allocation at a country level. LIRs can be Internet Service Providers (ISP) or organisations which manage their own IP Addresses such as banks, governments or universities.

History of the RIRs (2:56)

Task 3.1 Investigation and Acronyms

STAGE ONE : Research!

Visit the websites of all parties concerned and spend 5 minutes looking around to see what interesting information you can find. Write up what you have learnt in your notebooks.
  • ICANN - The Internet Corporation for Assigned Names and Numbers
  • IANA - The Internet Assigned Numbers Authority
  • NRO - The Number Resources Organisation
  • AFRINIC - The African Network Information Centre
  • APNIC - The Asia Pacific Network Information Centre
  • ARIN - The American Registry for Internet Numbers
  • LACNIC - Latin American and Caribbean IP Address Regional Registry
  • RIPE NCC - Réseaux IP Européens Network Coordination Centre
Share what you have found with the rest of the class.

STAGE TWO : Acronyms!

There are plenty of acronyms in this section. Make a list of all of them in your notebooks.

OUTCOME : Notes on the Internet Registry hierarchy

Click to read more!

One man

In the early days of the ARPANET and the fledgling Internet, it fell to one man to manage, organise and catalogue the allocation of internet numbers. For 30 years, the 'Czar' of assigned numbers, Jon Postel, personally issued internet numbers to members of the internet community and, allegedly, recorded them in a scrappy notebook.

Jon Postel is the Internet Assigned Number Authority, no joke.
  • First mention of Jon Postel recording number assignments - RFC739 (1977)
  • First mention of standard 32 bit IP addresses and network classes - RFC790 (1981)
  • Joyce Reynolds takes over assignment duties - RFC870 (1983)
  • First mention of IANA - RFC1060 (1990)

Activity 4 URLs, URIs and the DNS 

In the early days of the Internet, 'services' (i.e. computers running useful software remotely) were accessed by their IP Address. When there were only a few services available, this wasn't really an issue but as the Internet grew, humans (inherently bad at remembering lists of numbers) needed a more user friendly way of remembering where their favourite service was located, so, in 1983, the Domain Name System (DNS) was invented.

DNS Explained (6:03)

You can think of the DNS as a big address book where the service names are mapped to an IP address. These 'service names' not only tell us where a resource is located on the Internet but what it's called as well. In fact, as part of the effort to conserve the ever dwindling IPv4 address space, multiple services running on a private IP address space can be mapped to a single public IP address using Network Address Translation (NAT).

Task 4.1 Network Address Translation

Click me!

As the lady says 'Click me' and read about Network Address Translation. Write yourself some notes in your notebook or folder to explain a) how it works and b) why is it used. You must include ...
  • One image
  • Two application
  • Three advantages
OUTCOME : Network Address Translation

URLs and URNs

Uniform Resource Names (URN) tell us what a resource is called. Uniform Resource Locators (URL) tell us what a resource is called and where it is located. Together, URNs and URLs are called Uniform Resource Identifiers (URI).

We are most commonly used to using URLs to access resources on the Internet from web servers (let's call them 'web pages' for the sake of familiarity). The structure of a WWW URL is fairly simple ...

Click to enlarge and print a copy

The most important distinction is between a Domain Name and a Fully Qualified Domain Name (FQDN) which includes the host name. We can identify the components of a URL from the DNS Hierarchy (my best shot at it in any case) ...

Click to enlarge (dashed lines indicate alternatives)

In the diagram, TLD stands for Top Level Domain and SLD stands for Second Level Domain.

Task 4.1 DNS animation ('cause the one you've seen isn't good enough)

STAGE ONE : What a difference an 'FQ' makes!

In your own words, describe the difference between a Domain Name and a Fully Qualified Domain Name (FQDN).

STAGE TWO : Research!

To be honest, the video you watched should have cleared up most of the concerns about how the DNS operates. However, there are plenty of other great resources which will help you make sense of this. Spend some time looking over the following resources before you attempt the remainder of the task ...

New gTLDs : The Dot has new friends! (0:54)

STAGE THREE : Perform a DNS Trace

This is a very interesting challenge which shows in principle, how DNS requests traverse the logical structure of the DNS hierarchy. There aren't many working DNS trace tools online, but this one works very well ...

Click me to perform a DNS trace

Clicking this rather cute image will take you to the W3DT (stands for World Wide Web Domain Tools) website. There are plenty of tools on here that you can use to query the DNS. Click the cute picture and fill in the form in the following way ...

You can click me as well if you want!

Make sure that you tick the 'Trace from root-servers.net' box to make sure that the DNS Root Servers (.) are included in the trace results. Print out the results of the trace for your notebooks / folders. Highlight the Root server in  YELLOW , the TLD DNS servers in  ORANGE  and the 'Authoritative' IP Address in  BLUE .

STAGE THREE : Your own animation!

Use Powerpoint or a suitable animation package to create an animation to show how the DNS works.

OUTCOME : Animation to show how the DNS works.

Activity 5 The Dark Net (and the Dark Web)  INTERESTING EXTENSION

Even though this is not strictly on the specification of any examination board, it's still a subject that crops up a lot in conversation so (in my humble opinion), it's important that I devote at least a little real estate to it.

Click to enlarge

Interesting facts about the darkness of the net and the darkness of the web ...
  • Surface web : indexed by search engines. What 'Google' sees.
  • Deep web : Portion of the web not indexed by search engines – often buried deep within websites behind authentication pages or within databases.
  • Dark web : Portion of the web only accessible via special search engines like TOR (The Onion Router Project).
  • Dark net : either ‘lost’ hosts due to router malfunctions (dark address space) or unreachable hosts due to deliberate obscuration (Freenet).

  • Around 95% of internet traffic is TCP – lossless, connection-oriented packet transmission
  • Around 5% is UDP - connectionless, lossy traffic from streaming services
  • Less than 1% of other transmission protocols like ICMP

Task 5.1

There are plenty of interesting articles to read about this topic ...
OUTCOME : No specific outcomes, it's just interesting.

Extension Activities 

You could seriously spend the rest of your career on this topic alone. There are millions of hours of extension work should you wish to partake. However, here are some selections ...

How about these?
  • The Kingfisher Information Service website lists all the cables and offshore renewables around the UK so you don't accidentally snag them with your anchor.

  • Interesting YouTube video ...

    Who Invented the Internet (6:32)

  • When the ARPANET was finally decomissioned on February 28, 1990, Vint Cerf, co-architect of the TCP/IP stack, wrote this poem. Read it and weep.

  • If you are interested in learning more about IPv6 addresses, it's well worth reading through this document from SURF, the collaborative organisation for ICT in Dutch education and research.

  • Read more about IPv6 network address structure
    - Oracle documentation
    - RFC2374 IPv6 Global Unicast Address Format
    - MSDN IPv6 Addressing

  • Request for Comments 2468 remembering Jon Postel, the original 'IANA'.

  • TED Video reflecting on the first 5000 days of the Internet.

  • Detailed history of the Internet and the development of the Regional Internet Registries on APNICs website.

  • Visit the Internet Hall of Fame Internet Timeline - it's great!

  • Get your cap on backwards and watch Internet Class on YouTube!

What's next?

Before you hand your book in for checking, make sure you have completed all the work required and that your book is tidy and organised. Your book will be checked to make sure it is complete and you will be given a spicy grade for effort.