Telemedicine WS 09/10 Computer Networks - 1 Worzyk FH Anhalt computer networks Communication...

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



Netzwerk - Network




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



Netzwerk - Network




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



Netzwerk - Network




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



Netzwerk - Network




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



Netzwerk - Network




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)

Telemedicine WS 09/10 Computer Networks - 1 Worzyk FH Anhalt computer networks Communication...

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