Transcript Data Communications

ECOM 4314
Data Communications
Fall September, 2010
Instructor
Eng. Wazen M. Shbair
Department of Computer engineering , IUG
Master degree in Computer engineering
Research Scope: Network Security
Email: [email protected]
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Text Book
Data Communications and Networking,
4rdEdition, BehrouzA. Forouzan, McGraw-Hill,
2007.
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Grade Distribution
Discussion
20%
Mid-Term Exam
20%
Research paper
20%
Final Exam
40%
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Assignments, Quizes
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Lecture #1 Outline
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Overview
Data Communications
Networks
Protocols and Standards.
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Overview
 Data communications and networking are
changing the way we do business and the way
we live.
 Businesses and all aspects of live today
rely on computer
networks and
internetworks.
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Data Communications
 When we communicate, we are sharing
information either locally or remotely.
 The term telecommunication, which includes
telephony, telegraphy, and television, means
communication at a distance
(tele is Greek for "far").
 The word Data refers to information presented
in whatever form is agreed upon by the parties
creating and using the data.
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Data Communications
Data communications are the exchange of data
between two devices via some form of
transmission medium such as a wire cable.
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Data Communications
 The effectiveness of a data communications
characteristics: delivery, accuracy, timeliness,
and jitter.
 Delivery : The system must deliver data to the correct
destination.
 Accuracy: The system must deliver the data accurately
 Timeliness: The system must deliver data in a timely manner.
 Jitter: it refers to the variation in the packet arrival
time. (It is the uneven delay in the delivery of audio or video packets)
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Data Communications Components
 A data communications system has five
components
 Message
 Sender
 Receiver
 Transmission media
 Protocol
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Data Representation
 Information today comes in different forms such
as text, numbers, images, audio, and video.
 Information is represented as a bit pattern,
a sequence of bits (0s or 1s)
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Data Flow (Transmission mode)
 Communication between two devices can
be simplex, half-duplex, or full-duplex.
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Network
 A network is a set of devices (often referred to
as nodes) connected by communication links.
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Network Criteria
 A network must be able to meet a certain
number of criteria such as:
 Performance
 Reliability
 Security.
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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
inquiry and a response.
 The performance of a network depends on 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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Performance
 Performance is often evaluated by two
networking metrics: throughput and delay.
 We often need more throughput and less delay.
 The throughput is then calculated by dividing
the file size by the time
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Reliability
 Network reliability is measured by
 The frequency of failure
 The time it takes a link to recover from a failure.
 The network's robustness in a catastrophe.
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Security
 Network security issues include:
 Protecting data from unauthorized access
 Protecting data from damage and development
 Implementing policies and procedures for recovery
from breaches and data losses.
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Network Physical Structures
 A network is two or more devices connected
through links.
A link is a communications pathway that
transfers data from one device to another.
 There are two possible types of connections:
point-to-point and multipoint.
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Point-to-Point
 A point-to-point connection provides a dedicated
link between two devices.
 The entire capacity of the link is reserved for
transmission between those two devices.
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Multipoint
 Multipoint connection is one in which more
 than two specific devices share a single link
 When a message is sent every device on the
network “hears” it but only the intended
recipient “listens” to it.
 All nodes must “fight” for their turn to speak
(connection) or wait to be granted a turn.
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Physical Topology
 The term physical topology refers to the way in
which a network is laid out physically.
 The topology of a network is the geometric
representation of the relationship of all the links
and linking devices to one another.
 2 or more devices connected to a link
 2 or more links form a topology
 Basic topologies Mesh, Star, Tree, Bus, Ring
,Hybrid
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Mesh Topology
 Each device has a dedicated
point-to-point link.
 The term dedicated means that
the link carries traffic only
between the two devices it
connects.
 A fully connected mesh network
with n devices has n(n-1)/2.
 Each network device must have
(n-1) I/O ports
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Mesh Topology
 Advantages
 High throughput
each connection can carry its own data load, thus eliminating the traffic
problems that can occur when links must be shared by multiple devices.
 Robust
If one link becomes unusable, it does not incapacitate the entire system
 High Security
When every message travels along a dedicated line, only the intended
recipient sees it.
 Simple fault identification and isolation
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Mesh Topology
 Disadvantages
 Number of cables –space & cost ( material, install.)
 Number of I/O ports
 Difficult to reconfigure
 One practical example of a mesh topology is the
connection of telephone regional offices in which
each regional office needs to be connected to
every other regional office.
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Star Topology
 In a star topology, each device has a dedicated
point-to-point link only to a central controller,
usually called a hub.
 a star topology does not allow direct traffic
between devices. The controller acts as an
exchange
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Star Topology
 Advantages
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Less expensive (cable) than Mesh
One I/ O port
Easy to install and reconfigure
Robust
Easy to cope with fault
 Disadvantages
 More cabling used than for other topologies(such as ring or bus)
 Hub failure disables entire network
 Usage
 Ethernet
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Bus Topology
 A bus topology is one long cable acts as
a backbone to link all the devices in a network.
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Bus Topology
 Advantages
 Easy to install
 Less cable compare to other topologies
 Failure of any device does not shut network down
 Disadvantages
 Limited backbone length, number & distance between
taps
 Backbone failure causes complete network failure
 Fault isolation difficult
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Ring Topology
 In a ring topology, each device has a dedicated
point-to-point connection with only the two
devices on either side of it.
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Performance
 A signal is passed along the ring in one
direction, from device to device, until it reaches
its destination.
 Each device in the ring incorporates a repeater.
When a device receives a signal intended for
another device, its repeater regenerates the bits
and passes them along
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Performance
 Advantages
 Easy to install
 Easy to cope with fault
 Disadvantages
 Not robust
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Hybrid Topologies
 Larger networks often combine several
topologies connected via central hub or
backbone.
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Categories of Networks
 Three categories of Networks
 Local Area Network (LAN) limited to a few kilometers
 Metropolitan Area Network (MAN) tens of miles
 Wide Area Network (WAN) worldwide.
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Local Area Network (LAN)
 A local area network (LAN) is usually privately
owned and links the devices in a single
 office, building, or campus .
 a LAN can be as simple as
two PCs and a printer
in someone's home office.
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Metropolitan Area Networks
 A metropolitan area network (MAN) is a network
with a size between a LAN and a WAN.
 It normally covers the area inside a town or a
city.
 Mainly used for interconnecting private LANs
located at different areas to each other
 Normally owned and operated by someone else:
an independent or government service provider
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Wide Area Network
 A wide area network (WAN) provides longdistance transmission of data, image, audio, and
video information over large geographic areas
that may comprise a country, a continent, or
even the whole world.
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Internetworks
 Network of networks
 Connection via
interconnecting devices
(Routers & Gateway)
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Protocol Definition
 A set of rules for communication
 Need to be agreed on both sender and receiver
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Protocol Elements
 Syntax
 Structure or format of data
 Frame Format: Destination Add, Source Add, Data
 Semantics
 Meaning and action
 Does this Address belong to me?
 Timing
 When & How fast
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References
 Ayman, Maliha, “Data Communication Lectures”,
IUG.
 BehrouzA. Forouzan , “Data
Communications and Networking”,
4rdEdition, Chapter2, 2007
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Thanks
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