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Prepared by: Saatchi, Seyed Mohsen1 Arab Open University - AOU T171 You, Your Computer and the Net: Learning and living in the information age Session.

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Presentation on theme: "Prepared by: Saatchi, Seyed Mohsen1 Arab Open University - AOU T171 You, Your Computer and the Net: Learning and living in the information age Session."— Presentation transcript:

1 Prepared by: Saatchi, Seyed Mohsen1 Arab Open University - AOU T171 You, Your Computer and the Net: Learning and living in the information age Session 7 Section 4 & 5

2 Prepared by: Saatchi, Seyed Mohsen 2 From ARPANET to the Internet Module 2 - Section 4 Book reference: A brief history of the future, Chapter 10

3 Prepared by: Saatchi, Seyed Mohsen3 Arab Open University - AOU Main ideas covered in this section are: 1. Gateways 2. Transmission Control Protocol (TCP) 3. Internet Protocol (IP)

4 Prepared by: Saatchi, Seyed Mohsen4 Introduction Although the host computers connected to the ARAPNET were diverse, the actual network itself – that is the subnet of IMPs - was highly homogenous The IMPs were identical Run the same software This had made the process of monitoring, controlling and rebooting them from a control room is possible and easy The Internet is highly diverse and heterogeneous Links all kinds of different networks into one apparently seamless whole

5 Prepared by: Saatchi, Seyed Mohsen5 Introduction This section covers the story of how the transition was made from the homogenous ARPANET to the heterogonous Internet? The key was a new set of protocols,mainly TCP- Transmission Control Protocol IP- Internet Protocol Generally referred to as TCP/IP Because they (TCP,IP) highly linked together

6 Prepared by: Saatchi, Seyed Mohsen6 Casting the Net Beside ARPANET, several other packet-switched networks (systems) started operating The British NPL network (set up by Donald Davies) Cyclades network in France ALOHA packet-radio network in Hawaii The satellite network SATNET

7 Prepared by: Saatchi, Seyed Mohsen7 Casting the Net Although they were all packet-switched networks 1 - They were incompatible: Using different platforms. 2 - There was a serious problem in connecting these networks together: How to let them communicate and interact together, and comprehend each others?

8 Prepared by: Saatchi, Seyed Mohsen8 Casting the Net Vint Cerf had come up with a good solution to solve this problem, and connect those incompatible networks: 1- Using computers known as Gateways ( later known as Routers) between different networks 2- Making hosts responsible for end-to-end transmission of packets, together with error correction and retransmission if necessary 3- Devising the protocols necessary for performing the previous two tasks

9 Prepared by: Saatchi, Seyed Mohsen9 Casting the Net The required protocols were TCP IP Were developed by Vint Cerf and Robert Kahn The critical feature of TCP/IP was its open architecture Allowed the linking of any network to the rest of the networks via a gateway computer. TCP/IP enabled the huge growth of network connectivity to the Internet

10 Prepared by: Saatchi, Seyed Mohsen10 Anatomy of a packet Long messages are broken into smaller, equal-sized chunks called packets Switched through routers until they reach their destinations Software associated with the TCP/IP family of protocols takes care of the assembly, disassembly and addressing of packets

11 Prepared by: Saatchi, Seyed Mohsen11 Anatomy of a packet Packet Structure: packet is a string of bits divided into different segments

12 Prepared by: Saatchi, Seyed Mohsen12 Anatomy of a packet Those segments could be classified as follows: Headers (depend on the layers protocols) Application layers header Transport layers header Network layers header Source IP address Destination IP address Total length of the packet Time to live(time allowed for the packet to persist in the internet before being discarded by a router or host) Link layers header Payload or the data segment It is the core (chunk of the original message) Trailer

13 Prepared by: Saatchi, Seyed Mohsen13 Anatomy of a packet So in order to allow the payload (data segment) to pass through the Internet Extra information are added to it in a form of headers and trailer Each layer in the stack adds its own header to an outgoing packet and strips off (removes) the appropriate layers header from incoming packet

14 Prepared by: Saatchi, Seyed Mohsen14 Anatomy of a packet In the case of the packet illustrated in the diagram, for example, there are 4 layers of header. Reading from left to right the might correspond to the headers added by 1- An application (SMTP) Simple Mail Transfer Protocol 2- TCP 3- IP 4- Ethernet

15 Prepared by: Saatchi, Seyed Mohsen15 Anatomy of a packet

16 Prepared by: Saatchi, Seyed Mohsen16 Anatomy of a packet At more detailed level, each header it self has a specific structure, For example: 1- The TCP header

17 Prepared by: Saatchi, Seyed Mohsen17 Anatomy of a packet 2- The IP header May contain the following information Some miscellaneous information related to IP E.g., version The Internet address of the sending machine The Internet address of the destination machine Time to live To specify how long (in seconds) a packet is allowed to persist in the Internet before being discarded by a router or a host

18 Prepared by: Saatchi, Seyed Mohsen18 Anatomy of a packet Note! The protocols which underpin the Net have to specify things at a very detailed level But once they are agreed and tested, they can then become effectively invisible to us, the users, because computers handle them effortlessly in the background

19 Prepared by: Saatchi, Seyed Mohsen19 TCP/IP and your computer Any computer connected to the Internet has to speak the language of the networks protocols TCP/IP family of protocols (software) should be installed into the computer for accessing information (browsing) TCP/IP lunched when you initiated a dial-up connection In the early days of the Net, TCP/IP software had to be obtained separately or written specially for the operating system of a specific machine But nowadays, it comes with the operating system Windows, Unix, Linux, and Apple Mac

20 Prepared by: Saatchi, Seyed Mohsen20 TCP/IP and your computer The original version of TCP protocol was joining both TCP and IP features It was then split into two protocols TCP : To deal with their assembly and disassembly IP : To handle packet addressing

21 Prepared by: Saatchi, Seyed Mohsen21 TCP/IP and your computer The design philosophy behind this was the belief that it was better to have many specialized protocols Each did one job They co-operated with each others Rather than having one monolithic protocol That tried to do everything hard to be controlled and modified This is called the modular design

22 Prepared by: Saatchi, Seyed Mohsen22 TCP/IP and your computer Some Internet protocols used by your computer are Hypertext Transfer Protocol (HTTP) Allows you to get pages from Internet, and to communicate with the web (i.e. WWW) in general Simple Mail Transfer Protocol (SMTP) Used for sending and receiving Point-to-point protocol (PPP) Governs the transmission of IP packets over serial lines like the one running from a user modem to ISPs modem Others

23 Prepared by: Saatchi, Seyed Mohsen23 TCP/IP and your computer These protocols are designed and operated using layered approach Layered model of communications Each layer performs a specified Job and cooperates with the next layer Packets travel vertically up and down through the layers The protocols at each layer process the packets Pass them to the next layer / protocol

24 Prepared by: Saatchi, Seyed Mohsen24 TCP/IP and your computer For this reason, the TCP/IP software running on your computer is called TCP/IP stack When youre communicating with the Net, packets are going up and down through the stack

25 Prepared by: Saatchi, Seyed Mohsen25 Link Responsible for communicating with the hardware which connects your machine to the Net (e.g. the Ethernet card which connects you to the LAN and via a router to the Net, or the modem If you are using dial-up access). PPP LayerFunctionProtocols used Application Deals with applications programs used by the end-user. The protocols which reside at this level are embedded in the particular applications programs you use. SMTP, HTTP, FTP, Telnet Transport Deals with the disassembly and reassembly of packets, error detection and correction, etc. (i.e. the reliability and integrity of messages). TCP Network Deals with the addressing of packets (i.e. figuring out how to get packets to their destination). It gives no guarantees about whether packets will get through, it just decides where they will be sent. IP TCP/IP stack layers look like the following

26 Prepared by: Saatchi, Seyed Mohsen26 How a stack works? TCP/IP stack works by passing packets up and down from layer to layer Each protocol layer does something to the packet in order to achieve its purpose For example Each protocol layer in the stack adds its own header to an outgoing packet and strips off its own header from an incoming packet

27 Prepared by: Saatchi, Seyed Mohsen27 How a stack works? The link layer (bottom layer) The lower layer Responsible for communicating with the hardware which connects your machine to the Internet It can be an Ethernet card Connects you to a local area network (LAN) and via a router to the Internet

28 Prepared by: Saatchi, Seyed Mohsen28 How a stack works? In case of dial-up access the hardware is the modem which connects you to the Internet via an ISP (Internet Service Provider). Example: Point-to-Point Protocol (PPP) For an incoming packet: The link layer takes packets from the network wire (Local Area Network or modem) Removes any link layer header information (e.g., Ethernet information) Pass them to the network layer

29 Prepared by: Saatchi, Seyed Mohsen29 How a stack works? The Network layer Deals with addressing of the packets IP resides Responsible for figuring out how to get packets to their destination It gives no guarantees about whether packets will get through or not It just decides where they will be sent

30 Prepared by: Saatchi, Seyed Mohsen30 How a stack works? Example: Internet Protocol (IP) For an incoming packet: Checks whether the packet is corrupted or not If it is, discards it If it is OK It strips away any network layer header information Passes it to the Transport Layer

31 Prepared by: Saatchi, Seyed Mohsen31 How a stack works? The Transport Layer TCP resides Deals with the disassembly and reassembly of packets, error detection and correction, etc It ensures the reliability and integrity of messages Process them to and from the application layer above

32 Prepared by: Saatchi, Seyed Mohsen32 How a stack works? Example: Transmission Control Protocol (TCP) For an incoming packet: Checks to see if the packets have arrived in the order which they were sent (appropriate order of the packets) Reassembles them in the correct order, if they were unordered If a packet is missing E.g., because IP has rejected it as corrupted It requests a retransmission When the complete assembled packets is obtained, TCP passes them up to the Application layer

33 Prepared by: Saatchi, Seyed Mohsen33 How a stack works? The application layer At the top of the stack This is where the user interact with the network Deals with application programs used by the end-user The protocols which reside at this level are: SMTP: embedded in the particular application program you use to send and receive Telnet: embedded in the particular application program you use to login to a remote machine FTP: embedded in the particular application program you use to transfer files HTTP: embedded in the particular application program you use to browse web pages

34 Prepared by: Saatchi, Seyed Mohsen 34 Mass networking and its culture Module 2 – Section 5 Book reference: A brief history of the future, Chapters 11,12 and 13

35 Prepared by: Saatchi, Seyed Mohsen35 Introduction Users of the original ARPANET/ Internet were mainly the scientists and researchers (little social and political discussions) They were not open for the public However, the number of Internet users today is extremely large Almost everyone can have access to the Net

36 Prepared by: Saatchi, Seyed Mohsen36 Introduction Some of the factors that led to this critical change in the nature of the Net were: Usenet news Because it brought to networking large groups of people who felt that the proper function of the Net was to argue, discuss and enthuse about all topics that people interested in The global system of discussion groups Usenet emerged from the community of researchers and programmers who used the UNIX operating system Fidonet Network was built by hobbyists and enthusiasts An alternative to the Net

37 Prepared by: Saatchi, Seyed Mohsen37 Growth of alternative networks So the Usenet news was a way of exchanging news and opinions among large number of people It was emerged from the community of researchers and programmers who used the Unix Operating System Unix is a Multi-user time sharing operating system A Multi-user operating system allows more than one user to work on the machine at the same time A time-sharing system is a system that shares the CPU time among the users of the machine

38 Prepared by: Saatchi, Seyed Mohsen38 Growth of alternative networks Unix was created at Bell Labs The central research and development facility of AT&T company It was written by Ken Thompson and Denis Ritchie Denis Ritchie is the inventor of C language In 1974, AT&T decided to sell Unix for research institutions and universities for very cheap price Moreover, AT&T send the source code (the actual program written to produce the software) of UNIX with a license to change the source code

39 Prepared by: Saatchi, Seyed Mohsen39 Growth of alternative networks The Unix operating system spread rapidly among computer science department around the world So the main features that distinguished Unix from other operating system are as follows 1- It was the only powerful OS which could run on the minicomputers used in most universities 2- the source code was included, and the AT&T license included the right to alter the source code and share changes with other licensees

40 Prepared by: Saatchi, Seyed Mohsen40 Growth of alternative networks One major advantage of UNIX is the existence of Kernel An isolated small piece of code that can be easily placed in another machine, which will then run Unix Kernel is the core of OS Final stages of Unix was written in C language It is a high level language, that have the following advantages a- Easy to understand and modify (by computer scientists and also students) Made it easy for a programmer to add new function to the operating system b- C language is allowing UNIX to be Portable

41 Prepared by: Saatchi, Seyed Mohsen41 Growth of alternative networks As compared to Assembly language Low level language a- Difficult to understand and modify b- Machine specific If you have an assembly program running on one machine, it cant be used on another machine with a different architecture (not portable)

42 Prepared by: Saatchi, Seyed Mohsen42 Growth of alternative networks With the continual extensions and improvements to UNIX being made by its users, a need arose to incorporate these changes into updated versions and distribute them to the UNIX community So there was a need to be able to exchange new releases and features of Unix This need was achieved by developing a new program called UUCP (Unix-to-Unix copy program) Enabled users of Unix to import new Unix programs and releases As well as exchange some common discussions through a phone line (this was done for the first time)

43 Prepared by: Saatchi, Seyed Mohsen43 Growth of alternative networks UUCP leads to the creation of Usenet News It is a program that enabled people to post articles and notes to a shared location It can be read by other people that have access to that shared location Very close to nowadays conferencing system Each shared location was called a Newsgroup Which people can join based on their Interests

44 Prepared by: Saatchi, Seyed Mohsen44 Growth of alternative networks Usenet News spin-off Its main intention was as a utility device Used to exchange information about problems and solutions within the user community Now, it is used as a never-ending world wide conversations in all the topics

45 Prepared by: Saatchi, Seyed Mohsen45 Growth of alternative networks Unix and its Usenet News Was available for universities For students and academic staff And for industrial laboratories and business firms For researchers Available for Minicomputer users, not for PC users

46 Prepared by: Saatchi, Seyed Mohsen46 Growth of alternative networks PC users seek to create a networking system of their own ! This lead to the creation of Fidonet Build by hobbyists and enthusiasts It emerged from bulletin board technology as an alternative to the Net It was the first system, that allowed PC home users to receive and store information Then send it to other nodes in the network through phone lines This had increased the number of network users so rapidly

47 Prepared by: Saatchi, Seyed Mohsen47 Intellectual Property Intellectual Property is used to protect the right and companies to profit from their ideas products and books Intellectual property includes: Patents: which is mainly for new inventions Trade mark: which is used to identify and distinguish products Design: which is mainly for shape and appearance Copyright: which includes protection for books, music, fimls and software.

48 Prepared by: Saatchi, Seyed Mohsen48 Open source Open source was established by Richard Stallman, its main idea to have the software and its source code free and available for programmers to benefit from and improve in a cooperative manner. Intellectual property includes: Patents: which is mainly for new inventions Trade mark: which is used to identify and distinguish products Design: which is mainly for shape and appearance Copyright: which includes protection for books, music, fimls and software.

49 Prepared by: Saatchi, Seyed Mohsen49 The Open Source With new, commercial ideas, a tension occurs whether to to keep them private, for yourself Or share them with the world Registering the new product in a patent Protects it but… Reveals its details and makes it available for anyone who cares to examine the applications lodged with the Patent Office Not registering the product, in order to keep the design secret Rather than revealing how it works via a patent Threatened by the reverse engineering process Secrets will be revealed and might be stolen

50 Prepared by: Saatchi, Seyed Mohsen50 The Open Source So all of the previous assumes a commercial model – that the originator of a bright idea wants to profit from its exploitation Its source was hidden and no more open for improvements and change This was a shock for the computer research community The availability of Unix OS with its source code, was a very important factor in the development of the Internet

51 Prepared by: Saatchi, Seyed Mohsen51 The Open Source movement For non-commercial products, Open Source movement appeared Established by Richard Stallman It is main idea is to have the software and its source code free and available for programmers to benefit from and improve in a cooperative manner Where an originator is happy for others to closely examine and suggest improvements to the original concept; where profit is not a motivating factor but finding more 'elegant' solutions to a problem is more important e.g. the development of the UNIX operating system

52 Prepared by: Saatchi, Seyed Mohsen52 The Open Source movement Richard Stallman and the Free Software Foundation 1. The discovery that it was software which sold hardware rather than vice versa further reinforced the notion that the intellectual property embodied in a program could be exceedingly valuable 2. As software became commercially important, companies began to copyright their software and keep secret the source code at its heart 3. T his ran counter to the 'cooperative improvement' culture of the early users of the Internet

53 Prepared by: Saatchi, Seyed Mohsen53 The Open Source movement 4. In reaction to this and in an attempt to preserve the research culture of openness, Richard Stallman launched the Free Software Foundation, based on a new 'copy left' licensing system Grants to users of a program the right to alter its source code, provided they pass on the right to alter the revised code under the same terms

54 Prepared by: Saatchi, Seyed Mohsen54 The Open Source movement So, open source movement was established with an idea was To have the software and its source code free and available for programmers to benefit from and improve in a cooperative manner Its main intention Wasnt profit Rather finding solutions to problems, enhancing the product and coming up with more elegant version And preserving the research culture of openness (The early use of Internet)

55 Prepared by: Saatchi, Seyed Mohsen55 The Open Source movement The UNIX operating system was one of the key pieces of software at the heart of the development of the Internet, and a symbol for the practice of constantly making and distributing improvements to source code When UNIX became a commercial product and thus subject to protection from alteration, it sent a shockwave through the computer research community

56 Prepared by: Saatchi, Seyed Mohsen56 The Open Source movement The challenge was taken up first by Richard Stallman (again) and then, with greater long-term success, by Linus Torvalds and others Linux is a clear example of Open Source software Developed by Linus Torvalds Linux is an alternative operating system based on cooperative development and the copy left principle It is the PC version of Unix OS It is one of the best networking operating system Available free of charge Collectively this approach became known as the Open Source movement

57 Prepared by: Saatchi, Seyed Mohsen57 The Open Source movement In the last few years, the Open Source movement has attracted a great deal of attention in the computing industry and the media. The increased visibility of Open Source software is a product of several factors: 1. The current dominance of Microsoft in the software market has been challenged by the US Department of Justice 2. The decision in January 1998 by Netscape to release the source code of their browser 3. The discovery (by the mass media) of Linux, and its subsequent adoption in corporate applications 4. Promotion of the benefits and philosophy of the Open Source movement by influential figures 5. The realization that many key pieces of networking and web server software are in fact Open Source creations

58 Prepared by: Saatchi, Seyed Mohsen58 Values, theories and facts Values Facts are statements that people generally agree to be true Values are expressions of what they believe to be right, good, worthwhile, etc It's possible to have a rational argument about facts, but much more difficult to have one about values For example Two people might disagree about whether Bach was born before Beethoven - but both will probably agree that there is a neutral way of resolving the dispute by consulting a reference source that both accept as reliable But there is no analogous way of resolving a dispute about whether Beethoven was a better composer than Bach, because that dispute is really about values, not facts

59 Prepared by: Saatchi, Seyed Mohsen59 Values, theories and facts Values play a role in discussions about Open Source There are people, for example, who favor Open Source software simply because it is not made by Microsoft This may be because they believe that it's better than Microsoft's products, but such is their dislike of the micro software giant that some would probably choose an inferior product if it was the only non- Microsoft software that happened to be available

60 Prepared by: Saatchi, Seyed Mohsen60 Values, theories and facts Theories Then there are people whose views about Open versus Closed Source software are colored by their theoretical beliefs For example Economists tend to be suspicious of market dominance by a single company because they regard it as an impediment to the operation of free markets (e.g. it is very difficult for any company to enter the spreadsheet software development since Microsoft Excel is a de facto standard)

61 Prepared by: Saatchi, Seyed Mohsen61 Values, theories and facts Facts Given that software is an engineering construct, you would have thought that the easiest disputes to resolve would be those about the supposed technical superiority of Open Source software. Surely this at least is an empirical question that can be settled by experiment? It is not that simple. In late 1998, an internal Microsoft paper analyzing the Linux phenomenon was leaked to the Net. The paper suggested that the company saw Linux as a serious threat to its Windows NT (now Windows 2000) network operating system

62 Prepared by: Saatchi, Seyed Mohsen62 Values, theories and facts However, some experiments to compare NT and Linux were conducted by some company which shows that windows NT outperformed Linux These findings attracted a storm of protest from the Open Source community. Critics pointed out that the tests were paid for by Microsoft However, the company rejected these criticisms To the confused observer caught in the crossfire, it is difficult to know what the facts are

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