Transcript Management Information Systems

CLARK UNIVERSITY
College of Professional and Continuing Education
(COPACE)
Management Information Systems
Lection 04
Networks
Plan
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Basic terms
Classification of networks
Topology of networks
Model OSI
Types of environmental data
Basic terms
Computer network is a collection of
computers and other hardware
interconnected by communication
channels that allow sharing of resources
and information.
Basic terms
• Server
• Client
• Client-server
Basic terms
Computer entirely
dedicated to servicing
the requests of other
computers, plays the
role of a dedicated
server
Basic terms
Basic terms
The computer that combines the
functions of a client and a server,
is a peer node.
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Classification of networks
Speed of data
transfer
Environment data
transmission
Territorial
prevalence
Organization of
interaction of
computers
Classification of networks
Speed of data transfer:
Low speed
(less then 10
Мbit/sec)
Middle speed
(less then 100
Мbit/sec)
High speed
(more then 100
Мbit/sec)
Classification of networks
Territorial prevalence
Local networks
(LAN)
Speed:
10 Мbit/sec - 10 Gbit/sec
Global networks
(WAN)
Speed:
dozens Kbit/sec –
dozens Mbit/sec
Urban network
(MAN)
Speed:
dozens Mbit/sec
Classification of networks
Environment data transmission:
Wires network
Wireless
network
Classification of networks
Organization of interaction of computers:
Peer-to-peer
network
Network with
dedicated server
Hybrid network
Peer-to-peer network
Peer-to-peer network
Peer-to-peer operating systems include server
and client components of network services.
Examples:
 LANtastic
 Windows for Workgroups
 Windows NT Workstation
 Windows 95/98
Peer-to-peer network
Advantages:
1. Low price
2. Simplicity of installation and operation
Disadvantages:
1. Complexity of the information protection
2. Efficiency depends on the number of
computers
When do we use peer-to-peer networks?
1. Number of computers in the network
 10-20
1. Security problems are not critical
2. You don’t wait significant expansions of
your company
Network with a dedicated server
Network with a dedicated server
Advantages:
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Division of resources
Protection
Data backup
Big number of users
Disadvantages:
 Necessity of additional OS
for the server
 High complexity of
installation and
modernization of the
network
 Necessity of a separate PC
as a server
Hybrid network
Network topology
Network topology describes the
physical location of the computers,
cables and other network components
Network topologies
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Fully connected topology
Fully connected topology
It is the topology of a network in which each
workstation is connected to all the others.
The physical fully connected topology is generally too
costly and complex for practical networks, although the
topology is used when there are only a small number of
nodes to be interconnected
Bus topology
• Topology "bus" is a topology with a common cable
(called the bus), which is connected to all workstations.
• At the ends of the cable there are terminators to
prevent signal reflection.
Bus topology
When building large networks there is a problem if a
limited length of cables between nodes, in this case, the
network is divided into segments.
Segments are connected by various devices - repeaters,
concentrators or hubs. For example, the technology allows
the use of Ethernet cable up to 185 meters.
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Bus topology
Advantages:
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a little time of
setting up a
network
the cheapness
(requires less cable
and network
devices)
easy set-up
the failure of some
workstation does
not affect the work
of the whole
network
Disadvantages:
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any failures in the
network, as the cable
break, leads to the
failure of the whole
network
complex localization of
faults
The network
performance falls with
the addition of new
workstations
Star topology
"Star“ is the basic topology of a network in which all
computers are connected to the central node (usually a
switch or a hub), forming a physical network segment.
This segment can function
both individually and like
a part of a complex topology
as “tree”.
24-port switch
Advantages of star networks
• Better performance
• Isolation of devices
• We can increase the size of the network very
easily.
• Easy to detect faults and to remove parts.
Disadvantages of star networks
 failure of the central switch will result to an inability of
the network (or network segment)
 it often requires more cable than for most other
topologies
 number of workstations in the network (or network
segment) is limited by the number of ports in the central
switch
Ring topology
Ring is the basic topology of a network in which
workstations are connected sequentially to each
other, forming a closed network.
Advantages of ring topology
• ease of installation
• practically complete absence of the
additional equipment
• the possibility of stable work without a
significant drop in speed of data transmission
with heavy network traffic
Disadvantages of ring topology
 the failure of a single workstation, and other
problems (the cable break) leads to the
failure of the whole network
 the complexity of the configuration and
customization
 the complexity of troubleshooting
Star-bus (hybrid) topology
Tree topology
OSI model
• In 1984 the number of international standardization
organizations (ISO, ITU-T and others) developed the
Open System Interconnection model (OSI).
• The OSI model defines the different levels of
interoperability, gives them the standard names and
indicates which functions levels must perform.
OSI levels
Physical layer
It means the transferring of bits by
physical channels, such as a coaxial cable,
“twisted pair”, optic cable, wireless
networks.
Data link level
• This level is a very powerful and complete set
of functions for sending messages between
network nodes.
• It gives us the opportunity of detection and
correction of errors.
• Bits are grouped into sets called frames
Network layer
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Agreement of different technologies
simplification of addressing in large
networks.
Creation of reliable and flexible barriers
on the way of unwanted traffic between
networks.
Messages on this level are called
packages
Transport layer
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guaranteed delivery of data (it gives an
acknowledgement of reception of
packages)
detection of errors at the level of the
sender and recipient (it allows the host
system to detect bad packages)
Session layer
It manages the dialogue, i.e. it fixes which
side is currently active and provides the
synchronization
Presentation layer
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It works only with the form of data, without changing
the its content.
The information is always clear to the application
layer of another system.
Can overcome the syntactic differences in the data
models, or differences in the codes of characters,
such as ASCII codes
Encrypt data
Application layer
It gives a set of protocols which allow users an
access to shared resources, such as files, printers
or web-pages, and organizes their work together
Types of networks:
• Wires networks
• Wireless networks
Coaxial cable
Coaxial cable
Twisted pair
Optic fiber cable
Wireless networks
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The difficulty of cable laying
Mobility
Remoteness
Urgency
Bluetooth
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Bluetooth is designed for the construction of
personal wireless networks (Wireless
Personal Area Network, WPAN). The
coverage is up to 100 m
Line of sight is not required
Bluetooth works on the none-licensed in the
whole world frequency of 2.45 GHz, which
allows free usage of the bluetooth device.
The speed of 721 Kbps and the transfer of 3
voice channels
Wi-Fi
The most widespread technology of the organization of
wireless networks is WI-FI.
Speed of data transmission depends on the distance
between the points, and on other factors, for example,
on the level of interference.
At a speed of 54 Mbit/s, which is the limit for WI-FI, the
range is 30 to 50 m.
The distance increases up to several hundreds of meters
at a speed of 1 Mbit/sec.
IR-port
• IrDA (Infra red Data Association) allows you to
connect to peripherals without cables using
infrared waves.
• IrDA port operates at data rates 2400-115200
bit/sec.
• The main disadvantage is the need for direct
line of sight between the transmitter and
receiver.