Some Interesting Questions. Why do we have an Internet? How did it start? What is the difference between the Internet and the Worldwide Web?

Transcription

1 Some Interesting Questions Why do we have an Internet? How did it start? What is the difference between the Internet and the Worldwide Web?

2 And even more questions What is a Browser? What is a Search Engine? What is a link? What does at the start of a link mean? Why do some addresses start with

3 Remember these two?

4 Intercontinental Ballistic Missiles ICBM Mutually Assured Destruction

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6 Twelve Atlas F intercontinental ballistic missile sites were planned and constructed around parts of eastern Nebraska

7 THE ATLAS ICBM

8 The nuclear face-off in October 1962

9 How could NATO and the Western world ensure mutually assured destruction?

10 The key was indestructible and flexibly adaptable communications between missile sites

11 Genesis of The INTERNET The Internet started as ARPANET, a 1960s defence force project in the US which had the objective of connecting several super-computer sites in the country with one another so that if any one of them was destroyed by a nuclear explosion, for example, then the remaining computers would continue to function.

12 ARPANET ARPANET was the network that became the basis for the Internet. Based on a concept first published in 1967, ARPANET was developed under the direction of the U.S. Advanced Research Projects Agency (ARPA). In 1969, the idea became a modest reality with the interconnection of four university computers. ARPANET established the first ever computer-to-computer link on 29 th October 1969.

13 Packets and Protocols The Advanced Research Projects Agency Network (ARPANET) was an early packet switching network and the first network to implement the protocol suite TCP/IP. Together these technologies became the technical foundation of the Internet.

14 ARPANET LOGICAL MAP MARCH 1977

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16 Let s go back a bit Dial up communications the MODEM MODEM is a portmanteau word comprising MODulater and DEMODulater The MODEM is used to convert your message into a digital format which can be sent OUT over an analogue phone line and to convert INBOUND digital messages into a format that you can use

17 Dial up communications the MODEM MODEMs arrived long before the Internet and were used for dialling up a connection to (e.g.) bureau computing services The first MODEMs were associated with a phone handset The user had to dial up a service number; waiting until the right connection tone was established. Speeds were very low

18 BITs and BYTES The smallest atom of data is a BIT short for binary digit A BIT can either have value of 0 or 1 A BYTE is formed of 8 BITS, so can have a value between 0 and 255 So one BYTE can represent 255 different characters MODEM raw speeds are measured in BITS per second (bps) One megabit is 1,048,576 BITS One Kilobyte is 1024 Bytes One Megabyte is 1,048,576 Bytes One Gigabyte is 1,073,741,824 (or 2 30 ) Bytes or 8,589,934,592 bits Typically your PC will have a 4 megabits of random access memory

19 How many bytes do you really need? 1 Kilobyte will store 2 or 3 text paragraphs 1 Megabyte will store 873 pages of 1200 per page plain text 1 Gigabyte will store 4,473 books of 200 pages plain text OR 640 Web pages (1.6 Mb average size) OR 340 digital photos (3 Mb average size) OR 256 audio MP3 files

20 How fast is fast? bps The very first MODEM, used for linking Teletype machines bps AT&T introduce the first commercial computer modem 1980s 1200 bps First internal PC modem bps Hayes smart modem introduced. No more dial-up and wait 1980s onwards 4800 bps IBM dominate the scene but more 2400 modems come to market 1990s bps to bps Voice over IP. Modem prices continue to fall 1990s bps Theoretical limit reached for analogue phone lines 2000s ADSL arrives Asymmetric Digital Subscriber Line

21 How fast is fast? Between 1958 and the 2000s the speed has increased by a factor of over 500 and that s before FIBRE!

22 Going fully digital Asymmetric Digital Subscriber Line = ADSL The digital telecommunications signal is separated from the analogue phone signal by really clever techniques, which assure faster and faster rates of transmission and reception The line is ASYMMETRIC allowing for faster DOWNLOAD of data FROM the Internet but relatively slow UPLOAD of data TO the Internet

23 The ADSL filter The BT connection has just two wires to carry both phone and internet signals

24 And so to FIBRE - I Glass monomode fibres with diameter ten times narrower than a human hair are capable of transmitting data in the form of light. These fibre cables can transmit data many times faster than the copper wires used heretofore. BT Openreach has a massive distribution infrastructure of twisted pair copper cables from domestic premises which terminate in the familiar (light or dark) green boxes.

25 Inside the old fashioned BT street cabinet

26 Inside the new FTTC BT street cabinet

27 Fibre dimensions 1 mm = 1,000 microns Or 1,000 µm

28 Twisted pair dimensions Compared with monomode fibre

29 Fibre vs Copper Glass fibres are not subject to electromagnetic interference Attenuation of signals is many times less than that experienced with copper pairs Cross talk between fibres is eliminated Massively increased bandwidth available Elimination of security tisk cannot be tapped Great care needed to align junctions between fibres or at fibre terminations

30 And so to FIBRE - II FTTC Over the past fifteen years or so BT have been replacing the copper pair lines which carry signals between the green boxes cabinets and the exchange with optical fibre. This is a massive investment, known as FTTC, or Fibre to the Cabinet. It is FTTC which gives you speeds of up to 34 MB. Over 26 million homes or businesses now have FTTC Fibre.

31 The ultimate FIBRE connection FTTP. To replace the lines which travel between those green cabinets and your house is another much larger and more expensive step. This is known as FTTP, or Fibre to the Premises otherwise as Superfast fibre. FTTP can give download speeds of up to 1 Gbps. BT Openreach have already rolled out 345,000 installations and plan to meet two million by 2020

32 What is the Ethernet - I Ethernet is the most widely installed local area network (LAN) technology. Ethernet is a link layer protocol in the TCP/IP stack, describing how networked devices can format data for transmission to other network devices on the same network segment, and how to put that data out on the network connection.

33 What is the Ethernet - II Ethernet was developed at Xerox PARC* between 1973 and The idea was first documented in a memo that Metcalfe wrote on May 22, 1973, where he named it after the disproven lumeniferous ether as an "omnipresent, completely-passive medium for the propagation of electromagnetic waves". *Xerox PARC = Palo Alto Research Center

34 What is the Ethernet - III We now use the term very loosely when referring to Ethernet connections; Ethernet cables, etc An Ethernet cable is formed of 8 colour coded wires split into four Twisted pairs. The pairs are twisted in order to minimise crosstalk between adjacent pairs Signal carrying capacity is determined by the technical quality of the cables. The specifications refer to CAT5, CAT6, which specify if the cables are capable of carrying CAT5 can carry signals up to 100 Mbps CAT5E will work up to 1,000 Mbps (1 Gigabit) CAT6 still has four twisted pairs, but they are individually screened, so will work up to 10 Gigabit

35 An RJ45 Ethernet connector

36 Packets or Datagrams TCP/IP TCP Transaction Control Protocol IP Internet Protocol IEEE 802.x The international standard for packet switching

37 Think of it as sending POSTCARDS Each individual packet is like a postcard and has: A HEADER, which contains: A sender s address The recipient s address The date it was sent A sending number sequence Lots of other data about the type of postcard The header is followed by the CONTENTS Some information in a standardised format

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39 But each postcard is like an individual page of a novel being sent separately Random arrivals the post is often delayed The postcards can get routed by different paths around the Internet That is why each packet has an individual packet number as reference. When they are received they are all reassembled in the right order

40 But each postcard is like an individual page of a novel being sent separately Sometimes a packet gets lost (there is a page missing) If page 453 is received followed by page 455 the recipient needs to ask for a retransmission of page 454 Can you please confirm that you have received what I sent? Confirmation of receipt needed

41 But each postcard is like an individual page of a novel being sent separately Maybe there is a blot of ink on the postcard Page 11 was unreadable. Can you please resend it? Can we please keep our conversation secure? A massive can of worms - literally

42 Internet growth 1993 to 2016 (Worldwide Internet growth)

43 So much for the structure of the Internet But Tim Berners-Lee made it useful for all in 1989

44 The Worldwide Web Conceived by Tim Berners-Lee at CERN in 1989 Free to all. Three key concepts or tools Made it all possible

45 The three key tools of the WEB 1. HTML: HyperText Markup Language. The markup (formatting) language for the web. 2. URI: Uniform Resource Identifier. A kind of address that is unique and used to identify to each resource on the web. It is now commonly called a URL or Uniform Resource Locater. 3. HTTP: Hypertext Transfer Protocol. Allows for the retrieval of linked resources from across the web.

46 What is a BROWSER? A BROWSER is a software program. It is the entity that connects you to the WEB. You may be familiar with Microsoft s Internet Explorer, but other names may be familiar, such as Chrome; Safari; Firefox; Opera, and Microsoft s Edge. MS Windows PCs will default to Edge with effect from the introduction of Windows 10

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49 The SEARCH ENGINE The SEARCH ENGINE works in tandem with the BROWSER. Google is by far and away the most popular search engine

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54 Where is the data stored? Everything is stored in a DATA CENTRE. These data centres are all over the planet They will typically be in a highly secure building They consume an enormous amount of electricity Google has by far and away the largest number of data centres. Then there s Facebook, Amazon, Apple etc

55 Internet growth 1993 to 2016 (Worldwide Internet growth)

56 The Cloud aka many Data centres

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58 Save it to the cloud But at a cost!

59 No such thing as a free lunch!

60 The elephant in the room? Data centres are consuming 2% of global electricity

61 The elephant in the room? Internet connectivity is now becoming a significant contributor to global climate change

62 Google being cool...

63 Data centre images