Introduction to Networking Network Configuration Network Criteria Transmission Mode Network Topology

1. MTN 2013
Computer Network Technology
Chapter 2
Computer Network

2. Outline
1. Introduction to Networking
2. Network Configuration
3. Network Criteria
4. Transmission Mode
5. Network Topology
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3. 1. Introduction to Networking
• What is network?
• A network consists of 2 or more computers
connected together, and they can
communicate and share resources (i.e.
information)
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4. Why Networking?
• Sharing information — i.e. data communication
Do you prefer these?
Or this?
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5. Networking
• Sharing hardware or software
• E.g. print document
• Centralize administration and support
• E.g. Internet-based, so everyone can access the same administrative or support
application from their PCs
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6. How many kinds of Networks?
• Depending on one’s perspective, we can classify
networks in different ways
• Based on transmission media: Wired (UTP, coaxial
cables, fiber-optic cables) and Wireless
• Based on network size: LAN and WAN (and MAN)
• Based on management method: Peer-to-peer and
Client/Server
• Based on topology (connectivity): Bus, Star, Ring …
:
:
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7. 2. Network Configuration
• Form/arrangement/setup of network
parts/elements.
• Ways that computers can be connected
together to form networks.
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8. 3. Network Criteria
• To be considered effective and efficient, a network must meet a number
of criteria. The most important of these are performance, reliability, and
security.
Performance Reliability Security
Type of
Hardware Software
connection
Type of Frequency of
Catastrophe
transmission failure
Number of
user
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9. Performance
• Performance can be measured in many
ways, including transit time and response time.
• Transit time is the amount of time required for a
message to travel from one device to another.
• Response time is the elapsed time between an
enquiry and a response.
• The performance of a network depends on a
number of factors, including the number of
users, the type of transmission medium, the
capabilities of the connected hardware, and the
efficiency of the software.
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10. Number of User
• Having a large number of concurrent users can
slow response time in a network not designed to
coordinate heavy traffic loads.
• The design of a given network is based on an
assessment of the average number of users that
will be communicating at any one time.
• In peak load periods, however, the actual number
of users can exceed the average and thereby
decrease performance.
• How a network responds to loading is measure of
its performance.
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11. Type of Connection
– Point to Point - single transmitter and
receiver
– Multipoint - multiple recipients of single
transmission
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12. Type of Transmission
• Unicast, multicast, broadcast
• Transmission medium
– The medium defines the speed at which data can
travel through a connection. Today’s networks are
moving to faster and faster transmission
media, such as fiber-optic cabling, a medium that
can carry data at only 10 megabits per second.
However, the speed of light imposes an upper
bound on the data rate.
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13. Hardware
• The types of hardware included in a network
affect both the speed and capacity of
transmission. A higher-speed computer with
greater storage capacity provides better
performance.
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14. Software
• The software used to process data at the
sender, receiver, and intermediate nodes also affects
network performance.
• Moving a message from node to node through a
network requires processing to transform the raw data
into transmittable signals, to route these signals to the
proper destination, to ensure error-free delivery, and
to recast the signals into a form the receiver can use.
• The software that provides these services affects both
the speed and the reliability of a network link.
• Well-designed software can speed the process and
make transmission more effective and efficient.
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15. Reliability
• In addition to accuracy of delivery, network
reliability is measured frequency of failure, the
time it takes a link to recover from a
failure, and the network’s robustness in a
catastrophe.
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16. Frequency of Failure
• All networks fail occasionally.
• A network that fails often, however, is of little
value to a user.
• Recovery time of a network after a failure:
How long does it take to restore service? A
network that recovers quickly is more useful
than one that does not.
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17. Catastrophe
• Networks must be protected from
catastrophic events such as
fire, earthquake, or theft.
• One protection against unforeseen damage is
a reliable system to back up network software.
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18. Security
• Network security issues include protecting data from unauthorized access
and viruses.
Unauthorized access:
For a network to be useful, sensitive data must be protected from
unauthorized access. Protection can be accomplished at a number of
levels. At the lowest level are user identification codes and passwords. At
a higher level are encryption techniques. In these mechanisms, data are
systematically altered in such a way that if an unauthorized user intercepts
them, they will be unintelligible.
Viruses:
Because a network is accessible from many points, it can be susceptible to
computer viruses. A virus is an illicitly introduced code that damages the
system. A good network is protected from viruses by hardware and
software designed specifically for that purpose.
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19. 4. Transmission Mode
• Defines the direction of data flow between two
linked devices.
• The manner or way in which data is transmitted
from one place to another is called data
transmission mode.
• There are three ways for transmitting data from
one location to another. These are:
– Simplex
– Half duplex
– Full duplex
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20. Simplex Mode
• The communication can take place in only one direction.
• A terminal can only send data and cannot receive it or it can only
receive data but cannot send it.
• It means that in this mode communication is uni-directional.
• Today, this mode of data communication is not popular, because
most of the modem communications require two-way exchange of
data.
• However, this mode of communication is used in business field at
certain point-of-sale terminals in which sales data is entered
without a corresponding reply.
• The other examples of simplex communication modes are radio and
TV transmissions.
• Computer system, the keyboard, monitor and printer are examples
of simplex devices.
• The keyboard can only be used to enter data into computer, while
monitor and printer can only accept (display/print) output.
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21. Half/Semi Duplex Mode
• The communication can take place in both directions,
but only in one direction at a time.
• In this mode, data is sent and received alternatively. It
is like a one-lane bridge where two-way traffic must
give way in order to cross the other.
• In half-duplex mode, at a time only one end transmits
data while other end receives.
• In addition, it is possible to perform error detection
and request the sender to re-transmit information.
• The Internet browsing is an example of half duplex.
When we issue a request to download a web
document, then that document is downloaded and
displayed before we issue another request.
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22. Full Duplex Mode
• The communication can take place in both
directions simultaneously, i.e. at the same time on
the same channel.
• It is the fastest directional mode of communication.
• Example of this mode is conversation of the persons
through telephone.
• This type of communication is similar to automobile
traffic on a two-lane road.
• The telephone communication system is an
example of full duplex communication mode.
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23. 5. Network Topology
• The network topology defines the way in which
computers, printers, and other devices are connected. A
network topology describes the layout of the wire and devices
as well as the paths used by data transmissions.
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24. Bus Topology
Commonly referred to as a
linear bus, all the devices
on a bus topology are
connected by one single
cable.
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25. Bus Topology
• Advantages • Disadvantages
– It is easy to handle – The cable length is
and implement. limited. This limits the
number of stations
– It is best suited for
that can be connected.
small networks.
– This network topology
can perform well only
for a limited number
of nodes.
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26. Star & Tree Topology
The star topology is the most
commonly used architecture in
Ethernet LANs.
When installed, the star topology
resembles spokes in a bicycle wheel.
Larger networks use the extended
star topology also called tree
topology. When used with network
devices that filter frames or
packets, like bridges, switches, and
routers, this topology significantly
reduces the traffic on the wires by
sending packets only to the wires of
the destination host.
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27. Star Topology
• Advantages • Disadvantages
– Due to its centralized – The network operation
nature, the topology depends on the
offers simplicity of functioning of the
operation. central hub.
– It also achieves an – Hence, the failure of the
isolation of each device central hub leads to the
in the network. failure of the entire
network.
Hub
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28. Tree Topology
• A tree topology is a hierarchical computer
network that is a combination of star and bus
topologies.
• Allows for multiple hubs to exist on a network
which act as roots for terminals connected to
them.
• This tree like branched structure of networks
provides high scalability.
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29. Tree Topology
• Advantages • Disadvantages
– It is the best topology for a large - Dependence of the entire network
computer network for which a star on one central hub is a point of
topology or ring topology are unsuitable vulnerability for this topology. A
due to the sheer scale of the entire failure of the central hub or failure of
network.
the main data trunk cable, can
– Tree topology divides the whole cripple the whole network.
network into parts that are more easily
manageable. Tree topology makes it - With increase in size beyond a
possible to have a point to point point, the management becomes
network. difficult.
– All computers have access to their
immediate neighbors in the network
and also the central hub. This kind of
network makes it possible for multiple
network devices to be connected with
the central hub.
– It overcomes the limitation of star
network topology, which has a
limitation of hub connection points and
the broadcast traffic induced limitation
of a bus network topology. A tree
network provides enough room for
future expansion of a network.
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30. Ring Topology
A frame travels around the
ring, stopping at each node. If a node
wants to transmit data, it adds the
data as well as the destination address
to the frame.
The frame then continues around the
ring until it finds the destination
node, which takes the data out of the
frame.
Single ring – All the devices on the
network share a single cable
Dual ring – The dual ring topology
allows data to be sent in both
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directions. MTN 2013 30

31. Ring Topology
• Advantages • Disadvantages
– The data being – The failure of a single
transmitted between node of the network can
two nodes passes cause the entire network
through all the to fail.
intermediate nodes. – The movement or
– A central server is not changes made to
required for the network nodes affects
management of this the performance of the
topology. entire network.
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32. Mesh Topology
The mesh topology
connects all devices
(nodes) to each other for
redundancy and fault
tolerance.
It is used in WANs to
interconnect LANs and for
mission critical networks
like those used by banks
and financial institutions.
Implementing the mesh
topology is expensive and
difficult.
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33. Mesh Topology
• Advantages • Disadvantages
– The arrangement
– The arrangement of wherein every network
the network nodes is node is connected to
such that it is every other node of
the network, many of
possible to transmit the connections serve
data from one node no major purpose.
to many other nodes – This leads to the
redundancy of many of
at the same time. the network
connections.
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34. END
Q&A
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