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Telemedicine WS 09/10Computer Networks - 1
WorzykFH Anhalt
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
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Attributes ofCommunication
• Participants– Human to human– Application system to application
system– Human to application system
• Direction– Unidirectional versus bidirectional
• Dialogue
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Attributes ofCommunication
• Distribution– Number of recipient– Contextual recipient
• Nature– Oral, written, image
• Standard of communication• Distance (size / performance = time)• Trigger
– Push or pull
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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.
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Basic elements of a network
• Computers and nodes which are connected
• Infrastructure components which connect the computers
• wiring
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Client / Server
Offer resources and services to the public.One server canget ordersfrom several Clients
sends orders to a service provider.A Client can address several servers
Netz
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Categories of networks Private Netze öffentliche Netze
Local Area Network LAN
Metropolitan Area Network MAN
Wide Area Network WAN
Ausdehnung Firmengelände ca. 500 m
Region ca. 100 km
unbegrenzt
Geschwin-digkeit
10 - 100 Mbit/s
1 Gbit/s 155 - 622 Mbits/s
bis 64 kbit/s bis 2,5 Gbit/s
Anwendung Daten, Bilder
Daten, MM Daten, Sprache
Daten, Bilder
Daten, Sprache, Video
Technologie Ethernert, Token Ring
FDDI, DSL, Ethernet
DSL analog, ISDN
DSL
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Categories of networks
Private networks Public networks
Dimension
Speed
Application
Technologie
Local Area NetworkLAN
MetropolianArea NetworkMAN
Wide Area NetworkWAN
Campusca. 500 m
10 - 100Mbits/s
DataImages
EthernetToken Ring
1 Gbits/s
DataMM
FDDIDSLEthernet
Regionca100 km
155 - 622Mbits/s
DataSpeach
DSL
unlimited
bis 64Kbits/s
DataImages
analogISDN
bis 2,5 Gbits/s
Data, VideoSpeach
DSL
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transmission methods
• Direct connection between Client and Server
• Store and Forward network• Broadcast network
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Telephone: direct connection
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Internet: Store and Forward
Local network
Local Network
Internet
Data packet
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Radio: Broadcast
http://de.structurae.de/photos/index.cfm?JS=155487
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Topology of the computer connections
Star Ring Bus
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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
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Verkabelung
http://www.aces.utexas.edu/infrastructure/main.htm
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Heinrich - Braun - Krankenhaus Zwickau
http://www.hildebrand.at/Projekte/Krankenhausbau/body_krankenhausbau.html
http://www.hbk-zwickau.de/
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Zentralkrankenhauscentral - hospital
Klinikum Hannover Oststadt
http://www.klinikum-hannover.de/osk/index.htm
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Pavillon – KrankenhausPavilion - hospital
http://www.klinikum-hannover.de/nsk/index.htm
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Krankenhausverbundnetwork of hospitals
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Campus
http://www.med.uni-heidelberg.de/
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Primärverkabelungprimary cables
backbone
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ISO / OSIReferenzmodell
International Standards Organization
Open System Interconnect Reference Model
consists of 7 layers, which realise the different tasks of the data communication.
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ISO / OSI layers
http://www.interfacebus.com/Design_OSI_Stack.html
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ISO / OSI layers
Sicherung - Data Link
Physikalisch - Physical
Netzwerk - Network
Transport - Transport
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
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CablingPrimary cabling: between buildings
Fiber opticsCoaxial cableRadio relay system
Secundary cabling: main cable in building
Fiber opticsCoaxial cable
Tertiary cabling: within a floor (often a star)
Fiber opticsWLAN (radio network)Coaxial cable
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Fiber optics
Sender orSource
Analog /DigitalConverter
Driverunit
LED ReceiverPhototransistor
Fiber
Digital / AnalogConverter
Driverunit
transfer rate:200 Mbit/s to1 Gbit/s
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Twisted Pairtransfer rate :1 Mbit/s bis300 Mbit/s
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Coaxial cabletransfer rate :1 Mbit/s bis600 Mbit/s
http://en.wikipedia.org/wiki/Coaxial_cable
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transmission capacity
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WLAN Wireless local area network
Wi-Fi Wi-Fi Alliance
WECA (Wireless Ethernet Compatibility
Alliance)
Accesspoint
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Range of WLAN
Up to 100 m outdoor, Limited by• Walls• Ferroconcrete, Metal• Water
• Humide walls• Road-leaved trees
• Interferences with other equipment
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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
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ISO / OSI layers
Sicherung - Data Link
Physikalisch - Physical
Netzwerk - Network
Transport - Transport
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
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Ethernet
• Bus with 10Mbit/s and 100Mbit/s• Segments up to 500 m• Connection of segments with
repeaters– Bridges– Router (Weiterleiter)– Hub (Zentrum, Nabe)
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Ethernet CSMA/CD
Carrier Sense Multiple Access with Collision Detect
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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.
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Token Ring
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Connection elementsRepeater
A Repeater works at the physical layer. It repeats and apmlifies signals into a second segment.
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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.
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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.
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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.
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ISO / OSI Schichten
Sicherung - Data Link
Physikalisch - Physical
Netzwerk - Network
Transport - Transport
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
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TCP/IPObjectivs
• Independent of the network
technologie and the server
technologie
• All-purpose transmission
• End – to – end connection
• Standardised protocols
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ISO / OSI layers
Sicherung - Data Link
Physikalisch - Physical
Netzwerk - Network
Transport - Transport
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
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TCP/IPIP-Protokoll
• Selection of the route• Converting the global address to a
local address• Buffer of messages• Assemble fragmented messages• Avoiding infinite loops
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ISO / OSI Schichten
Sicherung - Data Link
Physikalisch - Physical
Netzwerk - Network
Transport - Transport
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
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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
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ISO / OSI Schichten
Sicherung - Data Link
Physikalisch - Physical
Netzwerk - Network
Transport - Transport
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
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Anwendungen
• HTTP : transmission of HTML• FTP : Filetransfer• email : electronical mail• telnet : Terminalemulation• NFS : Networkdata
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Formats for data exchange
• XML• EDIFACT• HL 7 (Helth Level 7)• ADT (Abrechnungsdatentypen)• BDT (Behandlungsdatentypen)