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Lecture 01

Lecture 01. We begin our lecture to ask ourselves a few simple questions for this subject such as: Have you used telecommunications? Examples! How do define “telecommunications”? why do we need it for? can we survive without it? Different modes of telecomm applications!

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Lecture 01

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  1. Lecture 01 • We begin our lecture to ask ourselves a few simple questions for this subject such as: • Have you used telecommunications? • Examples! • How do define “telecommunications”? • why do we need it for? • can we survive without it? • Different modes of telecomm applications! • The concept of convergence (to p2) (to p9) (to p13) (to p14) (to p15) (to p28)

  2. Examples of TelecommunicationApplications (to p3) 1) telephone, mobile phone Figure 1-5 2) use of Internet, web browser Figure 1-6 3) airline reservation systems • with combination of applications such as dial-up line as shown in Figures 1-7 & 1.8 4) ATM, Octopus Figure 1-9 5) automated remote water meter reading Figure 1-10 (to p4) (to p5) (to p7) (to p8) (to p1)

  3. FIGURE 1-5 Simplified diagram of the components of a standard telephone call. (a simple version) (to p2) (Note: we will learn more on how a telephone company works in the later lecture!)

  4. FIGURE 1-6 The telecommunications between a home computer and an Internet access provider. A version of dial-up service via telephone co Question: How does it differ, say, if you have subscripted a broadband service in HK? (to p2)

  5. FIGURE 1-7 The telecommunications connections between a traveler and an airline reservation computer through a local area network. Note: This dial-up approach still applied to most travel agents in HK, however its structure has changed substantially in this Internet age. How and why? (to p6) . More example

  6. FIGURE 1-8 The telecommunications connection between a traveler and an airline reservation computer through a leased line. Another version of dial-up application but -- This special line will provide a high speed and secure of Information retrieval. (to p2)

  7. FIGURE 1-9 An ATM connected to a computer by a telecommunications line. Note: This is a simple version of ATM Question: What competitiveness has this application received ? How does ATM work in HK? (to p2) .

  8. FIGURE 1-10 Remote reading of a water meter using telecommunications. Electricity Question: What adv has this application brought to Businesses? Can it applied to all cities over the world? (to p2) reserved.

  9. Telecommunications and Networking • What is Telecommunications? • Tele- • Communications • Telecommunications (to p10) (to p11) (to p12) (to p1)

  10. Definitions • Tele- • means by distance or distance apart (to p9)

  11. Definitions • communications • information pass from one place to another (to p9)

  12. Definitions • Telecom refers as comm between parties over a distance through electrical or electromagnetic means (conventionally!) • (note: we will spend more time to discuss more to understand what does it meant for through e means) (to p9)

  13. Why do we need Telecommunications? 1) merging of IS and networking to transmit information for business competitive power 2) obtaining information at the right place at a right time, eg digital phone to acquire local temperature 3) allowing geographic dispersion of facilities and people, such as telecommuting and e-commerce 4) allowing on-line marketing such as airline ticketing systems so that selling products can conduct directly, eg eBay, TaoBao (espeicall on Nov 11 in China) (to p1)

  14. Answer! Yes: If you like to live in a primitive form of a life style No: If you live in an modern society or an Informative world (to p57) (to p1)

  15. Way to classifying telecommunication applications • Consider Figure shown in the slide 16, we can classify each of these applications by their: • geography • Mode of connection (to p17) (to p23) (to p1)

  16. (to p15)

  17. geography • Local area network (LAN) • Metropolitan area network (MAN) • Wide area network (WAN) • Backbone • Personal Area Network (to p18) (to p19) (to p20) (to p61) (to p22) (to p15)

  18. Local area network (LAN) (device used to share resource between PCs in a Lab) (device used to connect LANs together) It composes of nodes And communication links (to p17) Server

  19. Metropolitan area network (MAN) (to p15)

  20. Wide area network (WAN) • covers a large geographic area and uses circuits provided by a common carrier • many made up of a combination of switched or leased, terrestrial and satellite, and private microwave circuits • typically span hundreds or thousands of miles and provide data transmission rates from 64Kpbs to 2Gpbs • Semantic view (to p21)

  21. (to p15)

  22. Personal Area Network A network of a few meters, interconnecting wireless devices such as PDA, Laptops, and other devices (to p15)

  23. Modes of connection • Fixed line connection • Wireless connection • Question: which mode should be acquired? And why? • Examples: home devices pic1, pic2, pic3 • Question: how to evaluate each of them above? (to p24) (to p25) (to p61) (to p62) (to p63) (to p15)

  24. Fixed line connection • Example: (to p23)

  25. Wireless connection • Wireless telephone connections • Satellite and microwave connection (to p26) (to p27) (to p23)

  26. Wireless telephone connections (to p25)

  27. Satellite and microwave connection (to p25)

  28. Convergence of technologies • Convergence, which refers to coming together of two areas or two companies, is happening at all levels in telecomm: • Products (local phone company Vs other phones in market such as BO; USB devices ) • Companies (IBM and Apple for PC or notebooks) • Technologies (fixed line vs Bluetooth or wireless) • How to connect them together? (to p29)

  29. Network Architecture • A reference model that describes the layers of hardware and software necessary to transmit data between two points or for multiple devices / applications to interoperate • Reference models are necessary to increase likelihood that different components from different manufacturers will converse • Two models to learn: OSI model and TCP/IP protocol suite (to p30)

  30. Standard models (to p31) • OSI • Compatibility • TCP/IP • Others • Mobile network • Concept of logical and physical connections in action (to p48) (to p49) (to p51) (to p60) (to p52)

  31. OSI • a worldwide organization known as ISO (International Standard Organization) established rules and standards to oversee all these issues for vendors whose wish to develop their products • In 1978, ISO proposed a telecomm architecture called: • Open System Interconnection (OSI) • The ISO-OSI model • the purpose of this model is to allow information/data interchange between different brands of devices • provides a basis for interconnecting dissimilar system/devices • How it works (to p32)

  32. ISO/OSI Model(cont.) • OSI uses an architecture of layer approach (a total of 7 layers) to represent the components of the total process of communication • (See Figure 3.2, p91) (to p32)

  33. (to p44) Level 1: Physical connection Levels 2-7: Logical connection (exist in the software only) (to p42) (to p41) (to p39) (to p37) (to p35) (to p34) (to p30) (to p47) Semantic view of their functions

  34. Layer 1: Physical link control layer • Layer 1: Physical link control layer • connectivity on physical linkage • allow bit streams from a device to flow onto the network • defines the electrical standards and signaling, that is how connections could be established and terminated • the only layer in which data transmission between devices takes place (to p33)

  35. Layer 2: Data link control layer • Layer 2: Data link control layer • defines standards for structured data into frames and sending frames across the network • it answers questions such as • 1. Where a frame starts or ends • 2. How errors are detected and corrected • 3. How to handle polling and addressing • 4. How machines are addressed (to p36)

  36. Layer 2: Data link control layer • Layer 2 (cont.) • it requires to work closely to devices such as modem/FEP • it controls the situation when data is received from the circuit faster than the receiver can handle it (it will slow down the transmission until further notice … this process is known as pacing) • note: IEEE fully subscribes to OIS architecture for the 802 standards for LANs (to p33)

  37. Layer 3: Network control layer • Layer 3: Network control layer • primary functions are network addressing and routing • generates acknowledgements that an entire message has been received correctly • responsible to break down messages end from layer 4 that suit for data transmission (to p38)

  38. Layer 3: Network control layer(cont.) • Layer 3 (cont.) • it decides which communication circuit to transmit data • it assembles data from blocks of bits before passing them up the level 4 (to p33)

  39. Layer 4: Transport control layer • Layer 4: Transport control layer • selects the route (if more than one is availble) the transmission will take between two devices • converts user addressing that is meaningful to network software and hardware • controls the flow of messages so that it will not over/under run of the speed of other devices • prevents the loss or duplication of entire messages (Note: Layer 2 is for frames) (to p40)

  40. Layer 4: Transport control layer (cont.) • Layer 4 (cont.) • multiplexing several streams of messages from higher levels onto one physical circuit and adding appropriate headers to messages to be transmitted to recipients • eg. Operators sends computer down time to all users in one command (to p33)

  41. Layer 5: Session control layer • Layer 5: Session control layer • temporary connection between machines/programs for exchange of messages • maintains and breaks a session between two systems/users • assign and control of priority to access and passing message to the systems (such as icq icon) (to p33)

  42. Layer 6: Presentation layer • Layer 6: Presentation layer • deals with the way data is formatted and presented to the users at the terminal • performs constant format for data transmission so that lower level would understand it • software perform data transformation to meet users’ need (such as different font size, characters per line etc.) (to p43)

  43. Layer 6: Presentation layer (cont.) • Layer 6 (cont.) • perform code conversion, data compaction, and data encryption • except data encryption, most aforementioned tasks are done by software in the host computer (to p33)

  44. Layer 7: Application or user layer • Layer 7: Application or user layer • is the ultimate end or data transmitted within the network • consists of application programs, and performs the communicating commands such as data editing, file editing etc • performs the following 6 major functions • 1. Common application service element (CASE), that is define standard events such as logon, password id. (to p45)

  45. Layer 7: Application or user layer(cont.) • Layer 7 (cont.) • 2. Job transfer and manipulation (JTM), defines standard to transfer batch jobs between devices • 3. File transfer, access and management (FTAM), defines standard for transfer of files between systems • 4. Message oriented interchange system (MOTIS), defines standard for interconnecting different system in the word • 5Office document architecture/office document interchange facility (ODA/ODIF), provides (to p46)

  46. Layer 7: Application or user layer(cont.) • Layer 7 (cont.) • 5. (cont.) a standard to allow the transfer, edit and return of documents across system from multiple vendors • 6.Virtual terminal services (VTS), defines the virtual terminal concept, including characters, graphics, image, colors etc (to p33)

  47. (to p33)

  48. Telecomm Arch. & Standards(cont.) The following two giants’ machines can also be linked to the telecomm. standards of ISO/OSI: • IBM developed the SNA (Systems Network Architecture) • DEC developed the DNA (Digital Network Architecture) (Note: many textbooks review these two architectures and we do not cover in this subject!) (Students who wish to gain a copy of these architectures can come to see me later!) (to p30)

  49. Telecomm Arch. & StandardsTCP/IP (cont.) • TCP/IP (Transmission Control Protocol/Internet Protocol),developed by USA Department of Defense, is also a commonly practiced now in industry • it consists of 5 (or 4) layers (namely, physical, network access, Internet, transport and application) (to p50) (to p30)

  50. Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer The OSI Model TCP/IP • Provides communications services for end user applications Application or Process Layer • Supports the accomplishment of telecommunications sessions • Supports the organization and transfer of data between nodes in the network Host-to-Host Transport Layer • Provides appropriate routing by establishing connections among network links Internet Protocol (IP) • Supports error-free organization and transmission of data in the network Network Interface Network Access • Provides physical transmission of data on the telecommunications media in the network Physical Layer (to p30) (to p59) Alternative view of 4 layers

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