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computer networks

computer networks. Communication Requirements for a network Topologie of computer networks ISO / OSI reference modell Variety of cables fiber optic cable Twisted Pair coaxial cable WLAN Wi-Fi transmission methods Ethernet Token Ring TCP / IP. Attributes of Communication.

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computer networks

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  1. computer networks • Communication • Requirements for a network • Topologie of computer networks • ISO / OSI reference modell • Variety of cables • fiber optic cable • Twisted Pair • coaxial cable • WLAN Wi-Fi • transmission methods • Ethernet • Token Ring • TCP / IP

  2. Attributes ofCommunication • Participants • Human to human • Application system to application system • Human to application system • Direction • Unidirectional versus bidirectional • Dialogue

  3. Attributes ofCommunication • Distribution • Number of recipient • Contextual recipient • Nature • Oral, written, image • Standard of communication • Distance (size / performance = time) • Trigger • Push or pull

  4. Requirements of a network • The speed must saisfy the partners. • The management of the components and the end devices as terminals, printers, ... must be simple • The operating expenses must be economically justifiable.

  5. Basic elements of a network • Computers and nodes which are connected • Infrastructure components which connect the computers • wiring

  6. Client / Server Offer resources and services to the public. One server can get orders from several Clients sends orders to a service provider. A Client can address several servers Netz

  7. Categories of networks

  8. Categories of networks Private networks Public networks Local Area Network LAN Metropolian Area Network MAN Wide Area Network WAN Dimension Campus ca. 500 m Region ca100 km unlimited Speed 10 - 100 Mbits/s 1 Gbits/s 155 - 622 Mbits/s bis 64 Kbits/s bis 2,5 Gbits/s Data Images Application Data MM Data Speach Data Images Data, Video Speach Technologie Ethernet Token Ring FDDI DSL Ethernet DSL analog ISDN DSL

  9. transmission methods • Direct connection between Client and Server • Store and Forward network • Broadcast network

  10. Telephone: direct connection

  11. Internet Local Network Local network Data packet Internet: Store and Forward

  12. Radio: Broadcast http://de.structurae.de/photos/index.cfm?JS=155487

  13. Topology of the computer connections Star Ring Bus

  14. Topologie • Star + When a cable breaks, only one component fails - Long cables • Ring + shortest cables, best transmission characteristic • When a cable breaks or one component fails, the whole transmission fails • Bus + most simple cabling - Problems with simultaneous transmissions

  15. Verkabelung http://www.aces.utexas.edu/infrastructure/main.htm

  16. Heinrich - Braun - Krankenhaus Zwickau http://www.hbk-zwickau.de/ http://www.hildebrand.at/Projekte/Krankenhausbau/body_krankenhausbau.html

  17. Zentralkrankenhauscentral - hospitalKlinikum Hannover Oststadt http://www.klinikum-hannover.de/osk/index.htm

  18. Pavillon – KrankenhausPavilion - hospital http://www.klinikum-hannover.de/nsk/index.htm

  19. Krankenhausverbundnetwork of hospitals

  20. Campus http://www.med.uni-heidelberg.de/

  21. Primärverkabelungprimary cablesbackbone

  22. ISO / OSIReferenzmodell International Standards Organization Open System Interconnect Reference Model consists of 7 layers, which realise the different tasks of the data communication.

  23. ISO / OSI layers http://www.interfacebus.com/Design_OSI_Stack.html

  24. Anwendung - Application Darstellung - Presentation Sitzung - Session Transport - Transport Netzwerk - Network Sicherung - Data Link Physikalisch - Physical ISO / OSI layers

  25. Cabling Primary cabling: between buildings Fiber optics Coaxial cable Radio relay system Secundary cabling: main cable in building Fiber optics Coaxial cable Tertiary cabling: within a floor (often a star) Fiber optics WLAN (radio network) Coaxial cable

  26. Fiber optics Sender or Source Analog / Digital Converter Driver unit LED Fiber Photo transistor Digital / Analog Converter Driver unit Receiver transfer rate: 200 Mbit/s to 1 Gbit/s

  27. Twisted Pair transfer rate : 1 Mbit/s bis 300 Mbit/s

  28. Coaxial cable transfer rate : 1 Mbit/s bis 600 Mbit/s http://en.wikipedia.org/wiki/Coaxial_cable

  29. transmission capacity

  30. WLAN Wireless local area networkWi-Fi Wi-Fi Alliance WECA (Wireless Ethernet Compatibility Alliance) Accesspoint

  31. Range of WLAN Up to 100 m outdoor, Limited by • Walls • Ferroconcrete, Metal • Water • Humide walls • Road-leaved trees • Interferences with other equipment

  32. Security of WLAN Without any precaution everybody in the range of communication can use the network an can put a trace on teh communication. Precaution: • MAC-Address: only dedicated equipment can use the network • WEP Wired Equivalent Privacy: 128 Bit Key, no more safe • WPA2 Wi-Fi Protected Access: 256 Bit Key

  33. Anwendung - Application Darstellung - Presentation Sitzung - Session Transport - Transport Netzwerk - Network Sicherung - Data Link Physikalisch - Physical ISO / OSI layers

  34. Ethernet • Bus with 10Mbit/s and 100Mbit/s • Segments up to 500 m • Connection of segments with repeaters • Bridges • Router (Weiterleiter) • Hub (Zentrum, Nabe)

  35. Ethernet CSMA/CD Carrier Sense Multiple Access with Collision Detect

  36. Token Ring • Before starting to transmit, the sender has to wait for a permission (Token). • All devices forward foreign packets. • When the data arrive at the receiver it will remove the data and forwards the empty token.

  37. Token Ring

  38. Connection elementsRepeater A Repeater works at the physical layer. It repeats and apmlifies signals into a second segment.

  39. Connection elements Hub A hub works at the physical layer. It is the center of a star topology which builds a logical bus.Like a bus, all connected devices get all transmitted information. Hubs can be cascaded.

  40. Connection elements Bridge A bridge works at the second level, the data link level. A bridge connects two segments. The bridge knows the addresses of both segments and forwards only those messages which are addressed to a device on the other side.

  41. Connection elements Router A router is a device with connections to at least two networks. It works at the third level, the network layer. A router can connect networks with different technologies.

  42. Anwendung - Application Darstellung - Presentation Sitzung - Session Transport - Transport Netzwerk - Network Sicherung - Data Link Physikalisch - Physical ISO / OSI Schichten

  43. TCP/IPObjectivs • Independent of the network technologie and the server technologie • All-purpose transmission • End – to – end connection • Standardised protocols

  44. Anwendung - Application Darstellung - Presentation Sitzung - Session Transport - Transport Netzwerk - Network Sicherung - Data Link Physikalisch - Physical ISO / OSI layers

  45. TCP/IPIP-Protokoll • Selection of the route • Converting the global address to a local address • Buffer of messages • Assemble fragmented messages • Avoiding infinite loops

  46. Anwendung - Application Darstellung - Presentation Sitzung - Session Transport - Transport Netzwerk - Network Sicherung - Data Link Physikalisch - Physical ISO / OSI Schichten

  47. TCP/IPTCP-Protokoll Main objective: safe transportation of data through the network • full-duplex virtual connection • Transmission as a stream • Sequenznumbers • sliding-Window-function • Controlled connection termination

  48. Anwendung - Application Darstellung - Presentation Sitzung - Session Transport - Transport Netzwerk - Network Sicherung - Data Link Physikalisch - Physical ISO / OSI Schichten

  49. Anwendungen • HTTP : transmission of HTML • FTP : Filetransfer • email : electronical mail • telnet : Terminalemulation • NFS : Networkdata

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