Download Computer Networking

Computer Networks
part I
Computer Networking
Networking began its infancy in the mid -1960’s.
by the US Department of Defence (DoD).
The original intention of networking was being
developed to withstand a nuclear war.
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Computer Networking
WE ARE DEALING WITH MACHINES INSTEAD OF
PEOPLE IN TODAY’S WORLD. OUR PRIVACY IS
AFFECTED AND ALMOST ALL OF OUR PERSONAL
INFORMATION CAN BE FOUND IN
THE “VIRTUAL WORLD” .
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Computer Networking
•
A collection of computing devices connected in
order to communicate and share resources.
Connections between computing devices can be
physical using wires or cables or wireless using radio
waves or infrared signals.
• Typically classified according to:
– Reach and complexity
– Protocols and topologies
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What is a Network?
• A network consists of 2 or more computers
connected together, and they can communicate and
share resources (e.g. information)
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BENEFITS OF A NETWORK
• Information sharing:
Authorized users can use other
computers on the network to access and share information and
data. This could include special group projects, databases, etc.
• Hardware sharing:
One device connected to a network, such
as a printer or scanner, can be shared by many users.
• Software sharing:
Instead of purchasing and installing a
software program on each computer, it can be installed on the
server. All of the users can then access the program from a single
location.
• Collaborative environment:
Users can work together on
group projects by combining the power and capabilities of diverse
equipment.
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Network Topologies
Introducing Topologies
• Topology refers to physical or logical arrangement of
network
• Physical topologies are
– Single Node
– Bus
– Star
– Ring
– Mesh
– Tree
– Hybrid
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Logical Topologies
• Refers to the way in which data are transmitted
between nodes
• Describes the way:
– Data are packaged in frames
– Electrical pulses are sent over network’s physical
media
• Logical topology may also be called network
transport system
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Single Node Topology
• Single device, at times device called dumb terminal is
connected to the server
• Devices operates on files from server and returns
them back after completing task
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Single Node Topology
• Advantages:
– Easy to install, configure and manage
– Least expensive
– Single cable is required
• Disadvantages:
– Network consists of single device
– Dumb terminal is dependent on server
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SIMPLE PHYSICAL TOPOLOGIES
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A Bus topology consists of a single cable—called a
bus— connecting all nodes on a network without
intervening connectivity devices
Bus topology network
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Bus topology
• All devices are connected to a common cable called
backbone/trunk
• Operates in daisy chain fashion
• Medium is shared that’s why creates collision
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Bus topology
• Advantages:
– Installation of devices is easy
– Works better for smaller network
– Less expensive
• Disadvantages:
– If backbone breaks, entire network gets down
– Difficult to isolate problems
– Limited number of devices can be attached
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Star topology
Every node on the network is connected through a
central device
A typical star topology network
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Star Topology
• Advantages:
– Easy to install, configure, manage and expand
– Centralized management
– Addition or removal of device does not affect the
whole network
• Disadvantages:
– Requires more cable
– Failure of hub affects entire network
– More Expensive
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Ring Topology
• Devices are connected in
a closed loop
• All devices have equal
access to media
• Device waits for its turn
to transmit
• Most common type is
Token Ring network
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Ring topology
Each node is connected to the two nearest nodes so the
entire network forms a circle
One method for passing data on ring networks is token
passing
A typical ring network
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Ring Topology
• Advantages:
– Reliable and offers greater speed
– No collisions
– Handles large volume of traffic
• Disadvantages:
– More cabling is required compared to bus
topology
– One faulty device affects the entire network
– Addition of devices affect network
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Dual Ring Topology
• Consists of two
independent primary
and secondary rings
• Secondary ring is
redundant, used only
when primary stops
functioning
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Fiber Distributed Data Interface (FDDI)
• Logical topology whose standard was originally specified by
ANSI in mid-1980s and later refined by ISO
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Mesh Topology
• Used in WANs to
interconnect LANs
• Every device is
connected to every
other device
• Use routers to
determine the best path
of communication
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Mesh Topology
Types
Full mesh
Partial mesh
• Full mesh topology – All devices are connected to
each other
• Partial mesh topology - Some devices are connected
to only those with whom they exchange most of the
data
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Mesh Topology
• Advantages:
– Improves fault tolerance
– Failure of one link does not affect entire network
– Centralized management is not required
• Disadvantages:
– Difficult to install and manage
– Each link from one device to other requires
individual NIC
– Expensive
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Tree Topology - I
• Combines the
characteristic of linear
bus and star topology
• Devices are wired to
root hub
• Twisted pair cable is
commonly used
• Lowest level devices are
smaller computers
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Tree Topology
• Advantages:
– Easy to expand the network
– Point-to-point wiring for each device
– Fault detection is easy
• Disadvantages:
– Difficult to configure
– If backbone breaks, entire network goes down
– More expensive
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Hybrid Topology
• Combines two or more different physical topologies
• Commonly Star-Bus or Star-Ring
• Also known as special topology and useful for
corporate offices
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Hybrid Topology
• Advantages:
– Used for creating larger networks
– Handles large volume of traffic
– Fault detection is easy
• Disadvantages:
– Installation and configuration is difficult
– More expensive than other topologies
– More cabling is required
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Hybrid Physical Topologies
Hybrid topology
Complex combination of the simple
physical topologies
Star-wired ring
Star-wired bus
Daisy-Chained
Hierarchical hybrid topology
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Hybrid Physical Topologies
Star-wired ring
Star-wired topologies use physical layout of a star in
conjunction with token ring-passing data transmission
method
A star-wired ring
topology network
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Hybrid Physical Topologies
Star-wired bus
In a star-wired bus topology, groups of workstations are starconnected to hubs and then networked via a single bus
A star-wired bus network topology
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Hybrid Physical Topologies
Daisy-Chained
A Daisy chain is linked series of devices
A daisy-chained star-wired bus topology
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Hybrid Physical Topologies
Hierarchical hybrid topology
Uses layers to separate devices by priority or function
A hierarchical ring topology
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