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Networks & Networking

Networks & Networking. MSI Lecture on 15th February 2003 By Dr.I.Sarafis. Computer Networks Concepts. Objectives describe components of telecommunications system calculate capacity of telecommunications channels & evaluate transmission media compare types of networks & network services

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Networks & Networking

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  1. Networks & Networking MSI Lecture on 15th February 2003 By Dr.I.Sarafis

  2. Computer Networks Concepts • Objectives • describe components of telecommunications system • calculate capacity of telecommunications channels & evaluate transmission media • compare types of networks & network services • compare alternative network services • identify applications for supporting electronic commerce, business

  3. Management challenges • Telecommunications revolution • Components, functions of telecommunications system • Communications networks • Electronic commerce & electronic business technologies 1. MANAGING LOCAL AREA NETWORKS: Must be carefully administered, monitored, vulnerable to interruption, data loss, viruses 2. MANAGING BANDWIDTH: While costs per unit are dropping and capacity is growing, sudden demand can overwhelm system

  4. Connection Types • Need for communication • Communication between 2 devices • Point-to-point • Multi subscriber communication • 3 -> 6 devices , 3 lines • 4 -> 12 devices , 6 lines

  5. The need for networks • Ν subscribers • Ν-1 devices • (Ν-1)/2 lines

  6. Communication Network Communication Node Terminal Node

  7. Network Uses

  8. Benefits of Networks • Resource sharing • Reliability • Money savings • Communication

  9. An example

  10. Convergence between I.T. & Telecommunications • No significant difference between processing of data (computers) and of telecommunication signals (communication equipment) • Unification between data, voice, video communications • Hard to distinguish between uni-processor computers, multi-processor systems, local area networks, wide area networks

  11. Network Services • Voice Networks • Information Transfer • Signaling • Call waiting, Caller ID, call redirection etc. • Data Networks • File, printer sharing • E-mail, ftp, chat, web • Videoconference, multimedia streaming • Unification of Services

  12. Communication Categories • Synchronous • Asynchronous Bit Series Network Bit Errors Packets Network

  13. Asynchronous communication categories • Connection oriented • Connectionless Network Connection oriented: packets are transmitted with the right order Network Connectionless: packets are transmitted with arbitrary order and without guarantied delivery

  14. Switching

  15. Multiplexing Multiplexer De-multiplexer Using multiplexing multiple sources are transmitted through the same physical medium

  16. Circuit Switching

  17. PBX Networks(Public Branch eXchange) Switching Node Public Telephone Networks are circuit switched

  18. Public circuit-switching network

  19. Packet Switching In packet switching information is broken in packets. Each packet is routed independently

  20. Switching techniques comparison • Circuit switching • Continuous channel occupation • Compatibility of transfer rate • No information processing • Packet switching • Better bandwidth allocation • Transfer rate conversion • Continuous operation under load • Packet priority techniques

  21. Asynchronous Transfer Mode (ATM) • New technology • Combines advantages of both techniques • Guarantied packet delivery (circuit switching) • Quality of Service (QoS) (circuit switching) • Effectiveness, flexibility (packet switching)

  22. Autonomous Packets (datagram)

  23. Digital & Analog sources Digital Source Digital Source Analog Source Analog Source

  24. Digital & Analog signals Amplitude Amplitude Time Time Digital Signals Amplitude Amplitude Time Time Analog Signals

  25. Advantages of Digital Technologies • Use of cheap digital circuits • Application of Integrated Circuits techniques • High security with the use of data cryptography • Integration of a variety of information (data, voice, video, text) • Easy signal repetition over long distances • Disadvantages • High bandwidth • Synchronization

  26. Data Coding

  27. Communication Protocols • What is it? • Specific procedures between devices • Followed with specific order • The “language” of communicating • Every day protocols example • Waiting for someone to finish talking before we start talking • Expressing pleasure when seeing someone after long time

  28. Network Architecture • Use of independent structural elements • Layered architecture • Layers/ levels • Transparent communication • Differences between architectures • Communication between incompatible devices • Is very complicated to handled by a single protocol • Use of layered & structured architecture

  29. Layered Architecture

  30. Layers, protocols & interfaces

  31. What Goes Wrong in the Network? • Bit-level errors (electrical interference) • Packet-level errors (congestion) • Link and node failures • Messages are delayed • Messages are deliver out-of-order • Third parties eavesdrop

  32. Advantages of Layered Architecture • Partitioning the problem • To small ones and • Easier to handle • Easy upgrade / addition of services • Since the necessary changes concern one layer only • General advantages of using modules

  33. The interface • Defines • The basic operations and services • That a layer offers to the higher one • Defines • The messages between neighbouring layers • Should be • Clear & explicit

  34. Architectures standards • System Network Architecture (SNA), IBM • Open Systems Interconnection (OSI), ISO • TCP/IP • Transfer Control Protocol / Internet Protocol • Architecture is • The collection of protocols, layers & interfaces

  35. OSI Model

  36. OSI Layers Application Layer Provides access to network services for the users Presentation Layer Cares for the proper data representation Session Layer Controls the communication process. Starts, ends and manages sessions and connections

  37. OSI Layers Transport Layer Cares for the reliable data transfer, for data flow control and for error correction Network Layer Isolates higher layers from transfer and switching technologies. Cares for data transfer through the proper route Data link Layer Ensures reliable information transfer on the physical media. Transfers frames with synchronization, flow control & error correction Physical Layer Deals with cabling issues and physical (electrical) bit transfer

  38. Network Categories(geographical) • Local Area Networks (LANs) • Wide Area Networks (WANs)

  39. ComparisonLAN / WAN • Different area size • Different implementation techniques • Different organizations • Different transfer rates (speeds)

  40. Standardization & Standards • What is it? • Benefits : • Independence from companies • Independence from architectures • Competitiveness Example: TCP/IP is a de facto standard and is documented with a large number of RFCs (Request for Comments). Despite the fact that it is not approved by any specific organization, TCP/IP is been used in the largest implemented network in the world, the Internet, instead of OSI which is official.

  41. Standardization Organizations • ISO (International Standards Organization) • ITU (International Telecommunication Union ) • IETF (Internet Engineering Task Force) • IAB (Internet Architecture Board) • ETSI (European Telecommunications Standards Institute) • ΕΛΟΤ (Greek Standards Organization) Note: Official standards firstly are been developed and then companies are trying to comply. On the other hand, de-facto standards are not becoming standards until they are recognized for their usability and efficiency.

  42. Integrated Services Networks • Integrated Services Digital Network, ISDN • narrowband ISDN • broadband ISDN ήB-ISDN • ΑΤΜ

  43. Integrated Services Networks Note: A Wide Area Integrated Network should provide high-speed integrated services (voice, data, video, images). It is expected that there will be a variety of applications that will take advantage of such networks. Applications like video-on-demand, video-conference and other bandwidth-intensive applications. To realize the consequences of high speed transfer rates, here is a simple example: a high resolution image (109 bits) would need over 4 hrs to be transferred through a 64 kbps line, 11 minutes through a 1.5 Mbps line and only 7 seconds through a 150 Mbps ATM line.

  44. Data Rate Requirements

  45. Network Topologies • Linear Bus - Ethernet/IEEE 802.3 10Base2 and 10Base5 • Star Wired Ring - Token Ring/IEEE 802.5 • Star Wired Bus - Ethernet/IEEE 802.3i 10BaseT • Dual Counter Rotating Ring - FDDI/ANSI X3T9.5 • Wireless - Product Specific

  46. Central Hub Star topology Node Node Node Node

  47. Node Data direction Transmitter Receiver Node Node Repeater Node Ring Topology

  48. Bus Topology Node Node Node

  49. Star-wired Bus Topology Node Node Node Node Node Node Concentrator Hub

  50. Physical Media • Physical media provide the connections between network devices that make internetworking possible. • There are four main types of physical media in widespread use today: • Coaxial Cable • Twisted Pair • Fiber Optic Cable • Wireless Media

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