Download computer networks

computer networks
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Communication
Requirements for a network
Topologie of computer networks
ISO / OSI reference modell
Variety of cables
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fiber optic cable
Twisted Pair
coaxial cable
WLAN Wi-Fi
• transmission methods
• Ethernet
• Token Ring
• TCP / IP
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Attributes of
Communication
• Participants
– Human to human
– Application system to application system
– Human to application system
• Direction
– Unidirectional versus bidirectional
• Dialogue
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Attributes of
Communication
• 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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sends orders to a
service provider.
A Client can
address several
servers
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Netz
Client / Server
Offer resources
and services
to the public.
One server can
get orders
from several
Clients
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Categories of networks
Private Netze
öffentliche Netze
Local Area Netw ork
LAN
Ausdehnung Firmengelände
ca. 500 m
M etropolitan Wide Area Netw ork
Area
WAN
Netw ork
M AN
Region
unbegrenzt
ca. 100 km
Geschw indigkeit
10 - 100
M bit/s
1 Gbit/s
155 - 622
M bits/s
bis 64 kbit/s
bis 2,5
Gbit/s
Anw endung
Daten,
Bilder
Daten, M M
Daten,
Sprache
Daten,
Bilder
Technologie
Ethernert,
Token Ring
FDDI, DSL,
Ethernet
DSL
analog,
ISDN
Daten,
Sprache,
Video
DSL
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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
Application
Data
Images
Data
MM
Data
Speach
Data
Images
Data, Video
Speach
Technologie
Ethernet
Token Ring
FDDI
DSL
Ethernet
DSL
analog
ISDN
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
Internet
Local Network
Local network
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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
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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
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http://www.aces.utexas.edu/infrastructure/main.htm
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Heinrich - Braun - Krankenhaus Zwickau
http://www.hbk-zwickau.de/
http://www.hildebrand.at/Projekte/Krankenhausbau/body_krankenhausbau.html
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Zentralkrankenhaus
central - hospital
Klinikum Hannover Oststadt
http://www.klinikum-hannover.de/osk/index.htm
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Pavillon – Krankenhaus
Pavilion - hospital
http://www.klinikum-hannover.de/nsk/index.htm
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Krankenhausverbund
network of hospitals
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Campus
http://www.med.uni-heidelberg.de/
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Primärverkabelung
primary cables
backbone
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ISO / OSI
Referenzmodell
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
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http://www.interfacebus.com/Design_OSI_Stack.html
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ISO / OSI layers
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
Transport - Transport
Netzwerk - Network
Sicherung - Data Link
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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
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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
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Twisted Pair
transfer rate :
1 Mbit/s bis
300 Mbit/s
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Coaxial cable
transfer rate :
1 Mbit/s bis
600 Mbit/s
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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
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
Transport - Transport
Netzwerk - Network
Sicherung - Data Link
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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 elements
Repeater
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
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
Transport - Transport
Netzwerk - Network
Sicherung - Data Link
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TCP/IP
Objectivs
• 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
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
Transport - Transport
Netzwerk - Network
Sicherung - Data Link
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TCP/IP
IP-Protokoll
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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
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
Transport - Transport
Netzwerk - Network
Sicherung - Data Link
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TCP/IP
TCP-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
Anwendung - Application
Darstellung - Presentation
Sitzung - Session
Transport - Transport
Netzwerk - Network
Sicherung - Data Link
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Anwendungen
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HTTP : transmission of HTML
FTP : Filetransfer
email : electronical mail
telnet : Terminalemulation
NFS : Networkdata
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Formats for data exchange
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XML
EDIFACT
HL 7 (Helth Level 7)
ADT (Abrechnungsdatentypen)
BDT (Behandlungsdatentypen)
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