Lecture 3: Introduction to Net-centric Computing

1. Lecture 3: Introduction to Net-centric Computing CSCI102 - Introduction to Information Technology B ITCS905 - Fundamentals of Information Technology

2. Overview • This Week • Background and history of networking and the Internet • Network architectures • The range of specializations within net-centric computing • Networks and protocols • Networked multimedia systems • Distributed computing • Mobile and wireless computing

3. Background Discussion Topics • Definitions • Describing a telecommunications system • Requirements for voice and data communications • History of telecommunications • Forces for change

4. Definitions • Communication • “A process which allows information to pass from a sender to one or more receivers” • “The science of transmitting information, especially symbols” • Tele • At a distance

5. Definitions • Telecommunications • “Communications over a distance”

6. Definitions • Circuit: • " A path over which two-way communications in any media occurs" • Line: • " A communications circuit which invariably uses a physical wire connection" • Link: • "A communications circuit is subdivided into segments known as links ”

7. Definitions • Channel: • A general definition would be "the part of a communications system that connects a message source with the message sink" • In this context a channel is "a one-way communications path“

8. Sound • If a tree falls in a forest far from any sound detector (such as a human ear or a microphone), does the tree's crash make any noise?

9. Sound • Sound depends on three things • There must be a vibrating source to set up sound waves • A medium (such as air) to carry the waves • A receiver to detect them

10. Sound • If a tree falls in a forest far from any sound detector (such as a human ear or a microphone), does the tree's crash make any noise?

11. Sound • The answer, of course, depends on how sound is defined

12. Sound • If it is thought of as the waves that are carried by the air, the answer is yes • Wherever there are sound waves there is sound • However, if sound is defined subjectively, as a sensation in the ear, for example, the answer must be no • In that case sound does not exist unless there is a receiver present to detect it • The two definitions are equally correct

13. Transmission Types • Analog: • " An analog signal is represented in the form of continuously varying physical quantities"

14. Transmission Types • Characteristics of analog signals: • Frequency (constant or varying over time) • Frequency range or bandwidth ( difference between the upper and lower frequencies) • Amplitude (varying over time)

15. Transmission Types • Analog signals are affected by a number of different types of noise and interference • These affect the signal clarity and include • White noise • Impulse noise • Signal to noise ratio • Distortion • Crosstalk

16. Transmission Types • Amplification of analog signals is necessary to counter signal distortion and attenuation • Transmission cables are likely to act as antennas and pick up background noise • This background noise is amplified as well as the signal • This noise is cumulative so the further an analog signal travels the more amplifiers it travels through  increased noise

17. 1 1 0 0 1 1 1 1 1 1 0 0 0 0 0 0 1 1 Transmission Types • Digital: • "A signal whose states are discrete intervals apart“ • Characteristics of digital signals: • Discrete and discontinuous • Unipolar or bipolar

18. Transmission Types • Any distortion that occurs while transmitting digital signals is recovered by regeneration using repeaters • Advantages of digital transmission: • Lower signal error • Lower noise levels • Increases line capacity • Less complexity • Integration of voice, data and images

19. Transmission Types • What type of signals are sound waves?

20. Describing a Telecommunications System • A telecommunications system can be described by its key components • Transmitter • Medium • Receiver • Communication network

21. Transmitter • Telephone, voicebox, terminal etc

22. Medium • Cable, air, data circuits etc

23. Receiver • Telephone, ear, computer etc

24. Requirements for Voice and Data Communications • Voice communications • Fast • < 200ms delay • Telco’s <70ms round-trip-delay • Speed more important than integrity • Data communications • Data integrity vs real-time

25. History of Telecommunications 1837 – Wheatstone and Cooke • five needle telegraph 1838 - Govt declines use of telegraph 1843 - First demonstration of Telegraph and FAX in US 1845 - Morse forms company 1851 - 50 telegraph companies operating 1856 - Western union telegraph (WUT) established

26. History of Telecommunications 1876 - WUT becomes the largest communications company - Alexander graham bell - patent on telephone 1876 - WUT decline to pay $100,000 for telephone 1877 - Bell company formed 1878 - Worlds first telephone exchange - Bell sues WUT and takes it over 1885 - AT&T established interconnections between regional telephone companies 1889 – First automatic telephone system

27. History of Telecommunications 1893/94 - Bell’s patent expires - Independent telephone companies enter the market 1911 - Bell associated companies formed 1913 - Vacuum tube patent

28. History of Telecommunications 1943 - Amplifiers and repeaters 1947 - Transistors 1956 - First trans-Atlantic cable laid 1957 - Launch of first satellite 1977 - Internet services provided by public carriers

29. History of Telecommunications 1984 - Divestiture in the US 1988 - Internet provides multimedia services - Global digital interconnectivity standards converge 1993 - Formation of global consortium for the development of global satellite and optical digital networks

30. What Caused the Internet ? • Sputnik I  • US government felt vulnerable  • Creation of Advanced Research Projects Agency

31. The Early Years • 1961 - First paper on packet-switching (PS) theory • 1962 - J.C.R. Licklider & W. Clark, MIT: "On-Line Man Computer Communication“ (August) • 1962 ARPA opened a computer research program and appointed to its head John Licklider to lead it • 1964 - Packet-switching networks;no single outage point

32. The Early Years • 1966/67 - plan for computer network system called ARPANETpublished • Independent teams at MIT, the National Physics Laboratory (UK) and RAND Corporation had all been working on the feasibility of wide area networks • Their best ideas were incorporated into the ARPANET design

33. The Early Years • Final requirement was to design a protocol to allow the computers to send and receive messages and data, known as an interface message processor (IMPs – see RFC 1) • Work on this was completed in 1968 • In October 1969, IMPs installed in computers at both UCLA and Stanford.

34. The Internet – 1969

35. The Internet – Later that year • see RFC 4: Network Timetable

36. LOG ERROR MESSAGE: The First Login

37. The Early Years • UCLA students would 'login' to Stanford's computer, access its databases and try to send data • The experiment was successful and the fledgling network had come into being

38. The Early Years • By December 1971 ARPANET linked 23 host computers to each other

39. From Arpanet to Internet • 1972, direct person-to-person communication that we now refer to as e-mail • host-to-host protocols (Telnet) • In October 1972 ARPANET went 'public'

40. TCP/IP design concepts • Crucial concept was that the system should have an 'open architecture‘ • Each network should be able to work on its own, developing its own applications without restraint and requiring no modification to participate in the Internet • Within each network there would be a 'gateway', which would link it to the 'outside world'

41. TCP/IP design concepts • The gateway software would retain no information about the traffic passing through • Packages would be routed through the fastest available route

42. TCP/IP design concepts • The gateways between the networks would • always be open • route the traffic without discrimination • Operating principles would be freely available to all the networks

43. Going Global - 1973 • First international connections to the ARPANET: university college of London (England) via NORSAR (Norway) • Ethernet • RFC 454: file transfer specification • Christmas day lockup

44. The Rest of the Seventies • 1974 - transmission control protocol/internet protocol (TCP/IP) • 1975 • Operational management of Internet transferred to DCA (now DISA) • First ARPANET mailing list is created by Steve Walker • 1978 - TCP split into TCP and IP (March)

45. The Rest of the Seventies • 1979 • Computer science department research computer network • Usenet • First MUD, MUD1 • Internet configuration control board (ICCB) • Packet radio network (PRNET) experiment starts with DARPA funding • April 12 emoticons

46. 1980’s Expansion • The 1980’s saw a period of expansion in the internetworking community • 1981 • BITNET, the "because it's time network" • CSNET (computer science network) • True names by Vernor Vinge • RFC 801: NCP/TCP transition plan

47. 1980’s Expansion • 1982 • DCA and ARPA establish the transmission control protocol (TCP) and internet protocol (IP), as the protocol suite for ARPANET • DoD declares TCP/IP suite to be standard for DoD

48. 1980’s Expansion • 1983 • Cutover from Network Control Protocol (NCP) to TCP/IP (1 January) • 1984 - Domain Name System (DNS) introduced

49. 1980’s Expansion • 1986 • NSFNET created (backbone speed of 56Kbps) • Internet Engineering Task Force (IETF) • Internet Research Task Force (IRTF) • 1987 • Number of hosts breaks 10,000

50. 1980’s Expansion • 1988 • 2 November - Internet worm • CERT (Computer Emergency Response Team) • DoD chooses to adopt OSI and sees use of TCP/IP as an interim