Transcript Chapter 1 Introduction

‫رقم المادة ‪CS416 :‬‬
‫شعبـــــــة ‪SB :‬‬
‫‪Spring 2008‬‬
‫الوقت ‪9-8 :‬‬
‫السبت – االثنين ‪ -‬االربعاء‬
‫الكتاب ‪Data communication and networking :‬‬
‫لغة الكتاب ‪English :‬‬
‫درجات المادة‬
‫‪5‬‬
‫درجات واجب‬
‫‪5‬‬
‫درجات حضور‬
‫‪15‬‬
‫اختبار أول‬
‫‪20‬‬
‫اختبار ثاني‬
‫‪25‬‬
‫اختبار ثالث‬
‫‪30‬‬
‫درجة نهائي‬
Chapter 1
1.
2.
3.
4.
5.
Introduction
Data Communication
Networks
Protocols and Standards
Standard Organizations
Introduction
Data communications and networking
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Change the way we do business and the way we live
Decision depends on accurate information
Business today rely on computer networks and
internetworks
Before get hooked up, we need to know:
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How networks operate
What types of technologies are available
What design best fills which set of needs
Introduction
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Development of the PC changes a lot in business,
industry, science and education.
Same happened to data communication and networking
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Possible for communications links to carry more and faster
signals
Services extended to have telephone services:
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Conference calling
Call waiting
Voice mail
Caller ID
Data Communications
Communication:
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Means sharing information
– Local (face to face) or remote (over distance)
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Telecommunication
– Telephone, telegraph and television
– Means communication at a distance
– Tele is Greek for far
Data Communications
Data:

Refers to information
– Presented in any form
– Agreed upon by the parties ( creating & using)
Data communication : is the exchange of data
between two devices via some form of
transmission medium (wire cable).
Data Communications
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Communication system made up of a combination of
hardware (physical equipment) and software (programs)
Effectiveness of data communication system depends:
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Delivery : The system must deliver data to correct destination.
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Accuracy: The system must deliver data accurately (no change).
–
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by intended device or user
Data changed is unusable
Timeliness: The system must deliver data in timely manner
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Data arrived late are useless
In the same order (video and audio)
Data Communications
Components
A data communication system is made up of five
components
Components
Message: the information (data) to be communicated
1.
Consist of text, numbers, pictures, sound, or video
Combination of any
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Sender: the device that sends the data message
2.
Computer, workstation, telephone handset, video camera …
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Receiver: the device that receives the message
3.
Computer, workstation, telephone handset, television ….
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Medium: The transmission medium is the physical path
by which a message travels from sender to receiver
4.
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twisted pair, coaxial cable, fiber-optic, radio waves
Components
Protocol: a set of rules that govern data
5.
communications
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An agreement between the communicating devices
Devices may be connected but not communicating (no protocol)
French speaker with Japanese speaker
Data Representation
Text
Numbers
Video
Images
Audio
Direction of Data Flow
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Communication between two devices can be:
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Simplex
Half-Duplex
Full-Duplex
Simplex (one way street)
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The communication is unidirectional
Only one device on a link transmit; the other can only receive
Direction of Data Flow
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Half-Duplex (one-lane with two-directional traffic)
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Each station can both transmit and receive, but not at the same
time.
One is sending, the other can only receive, and vice versa
The entire capacity of a channel is take over by the device is
transmitting
Direction of Data Flow
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Full-Duplex (two-way street)
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Both stations can transmit and receive at same time
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Signals going in either direction sharing the capacity of the link
Sharing can occur in two ways:
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Link has two physically separate transmission paths
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One for sending and the other for receiving
The capacity of the channel is divided between signals traveling in both directions.
NETWORKS
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A Network : A set of devices (nodes) connected
by communication links
Nodes : computer, printer
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Distributed Processing :
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Most networks used it
task is divided among multiple computers.
NETWORKS
Network Criteria
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Network must meet a certain number of criteria
Performance measured by:
1.
transit time: A mount of time required for a message to travel from one
device to another
2. response time: Elapsed time between an inquiry and a response

Performance depends on :
1- Number of users : large number slow response time.
2- Type of transmission medium : fiber-optic cabling faster than
others cables.
3- Capabilities of the connected hardware : affect both the speed
and capacity of transmission.
4- Efficiency of the software : process data at the sender and
receiver and intermediate affects network performance.
NETWORKS
- Reliability is measured by:
1- Frequency of failure: it is little value to a user.
2- Recovery time of a network after a failure
3- Network’s robustness a Catastrophe: protect by good
back up network system
- Security : protecting data from unauthorized access
NETWORKS
Type of connection
Defines the attachment of communication devices to a link
Piont-to-Point
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Dedicated link between two devices
Entire of the link is reserved between those two devices
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Use an actual length of wire or cable
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NETWORKS
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but other such as microwave or satellite is possible
Television remote control
NETWORKS
Multipoint (multidrop)
o
more than two devices share a single link
• Capacity is shared
•Channel is shared either spatially or temporally
• Spatially shared : if devices use link at same time
• Timeshare : if users must take turns
NETWORKS
Physical Topology: The way 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 (nodes) to each
other.
– Four topologies : mesh, star, bus, and ring
Topology
Mesh
Star
Bus
Ring
PHYSICAL TOPOLOGY
Mesh
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Every link is dedicated point-to-point link
•
To link n devices fully connected mesh has n(n-1)/2
physical channels
PHYSICAL TOPOLOGY
Example:
– 8 devices has links in mesh is n(n-1)/2
– number of links = 8 (8-1)/2=28
– number of ports per device = n – 1 = 8 –1 = 7
PHYSICAL TOPOLOGY
Advantages:
– Each connection carry its own data load
– A mesh topology is robust
– Privacy or security
– Fault identification and fault isolation
Disadvantages:
– Installation and reconnection are difficult
– Big a mount of cabling
– Big number of I/O ports
– Hardware connect to each I/O could be expensive
It is implemented as a backbone of hybrid network
PHYSICAL TOPOLOGY
Star
- Dedicated point-to-point to a central controller (hub)
- No direct traffic between devices
– The control acts as an exchange
PHYSICAL TOPOLOGY
Advantages:
- Less expensive than mesh ( one I/O port )
- Easy to install and reconfigure
- Less cabling
- Additions, moves and deletions required one connection
- Robustness : one fail not affect others
– Easy fault identification and fault isolation
Disadvantages:
- More cabling than other topologies ( ring or bus)
PHYSICAL TOPOLOGY
Bus
- it is multipoint
- one long cable acts as a backbone
•Nodes connect to cable by drop lines and taps
- Limit of number of taps and the distance between taps
- Signal travels along the backbone and some of its
energy is translate to heat
PHYSICAL TOPOLOGY
Advantages:
- Ease of installation
- Less cables than mesh, star topologies
Disadvantages:
- Difficult reconfiguration and fault isolation ( limit of taps)
adding new device required a modification of the
backbone
- Fault or break stops all transmission
PHYSICAL TOPOLOGY
Ring
- Each device has dedicated point-to-point line configuration
- Each devices incorporates a repeater
- Easy of install and reconfigure
- Connect to immediate neighbors
- Move two connection for any moving
- Easy of fault isolation
Disadvantage
- One broken device can disable the entire network (unidirectional)
PHYSICAL TOPOLOGY
CATEGORIES OF NETWORKS
o Local Area networks
o Metropolitan area networks
O Wide area networks
Network
Local-area network
Metropolitan-area network
Wide-area network
(LAN)
(MAN)
(WAN)
CATEGORIES OF NETWORKS
We decide the category depending on:
o Size
o
o
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Ownership
Distance it covers
Physical architecture
Local Area Network (LAN)
• Private owned
• Links the devices in a single office, building or campus
Local Area Network (LAN)
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1.
As simple as two PCs and a printer
Limited to few kilometers
LAN allow resources to be shared (hardware, software and data)
LAN distinguished by:
Number of Users:
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2.
3.
4.
LAN links a workgroup of task-related computers
Software on a server and accessed by clients
LAN size determined by
 Licensing restrictions on the number of user per copy of software
 Restrictions on the number of users licensed to access the OS
LAN uses one type of transmission medium
LAN topologies : bus, ring and star
LAN data rate: 4 to 16 Mbps (Today 100 Mbps)
Metropolitan Area Network (MAN)
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Cover a city (company offices in city)
MAN could be
– Single network : cable TV network
– Many LANs
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Example: company uses MAN to connect the LANs in a city
Owned by private company or by a public company (telephone
company)
Wide Area Network (WAN)
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Cover country, continent or whole world
WAN uses public, leased, or private communication equipment
Enterprise network: WAN owned by single company
Internetworks
Two or more networks are connected together
THE INTERNET
The Internet has revolutionized many
aspects of our daily lives. It has affected
the way we do business as well as the way
we spend our leisure time. The Internet is
a communication system that has brought
a wealth of information to our fingertips
and organized it for our use.
THE INTERNET

Network: group of connected communicating devices (computers and printers)
 An internet (small i) is two or more networks
 Notable internet is called the Internet (hundreds of thousands interconnected
networks)
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Private individuals + government agencies + school + research facilities +
Corporations + libraries in more than 100 countries
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This communication system came in 1969
Mid-1960 (ARPA) Advanced Research Projects Agency in (DOD) was
interested to connect mainframes in research organizations
 1967, ARPA presented its ideas for ARPANET
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Host computer connecting to (IMP) interface message processor.
Each IMP communicate with other IMP
1969, four nodes (universities) connected via IMPs to form a network
– Software (NCP) Network Control Protocol provided communication
between the hosts.
 1972, Vint Cerf and Bob Kahn invented (TCP) Transmission Control Protocol
THE INTERNET

Later TCP was split to (TCP) Transmission Control Protocol and (IP)
Internetworking Protocol
Internet Today
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Made of many wide- and local-area networks
Every day new networks area added and removed
(ISP) Internet services Providers offer services to the end users
– International service providers
– National service providers
– Regional service providers
– Local service providers
PROTOCOLS AND STANDARDS
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Protocols synonymous with rule
Standards are agreed-upon rules
Protocols
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Defines:
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What is communicated
How is communicated
What it is communicated
Elements of a protocol are
1- Syntax : structure or format of the data ( order they presented)
example : first eight bits is address of sender
second eight address of receiver
rest message.
PROTOCOLS
2- Semantics : meaning of each section of bits.
– How is a particular pattern to be interpreted
– What action to be taken based on the interpretation?
Ex : does an address identify route or final destination
3- Timing : identify when data should be sent and how fast they can be
sent.
EX: Overloaded and lost if sender 100 Mbps and receiver at 1 Mbps
STANDARDS
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Essential in creating and maintaining an open and competitive market for
equipment manufactures
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Guaranteeing national and international interoperability of data and
telecommunication technology and processes
Data communication standards are:
1.
De facto standards : (by fact) approved by widespread use
De Jure standards : approved by officially recognized body.
STANDARDS
Standards Organizations developed by:

Standard Creation Committees
– (ISO) International Organization for Standardization
– (ITU-T) International Telecommunication Union – Telecommunication
Standards Sector
– (ANSI) American National Standards Institute
– (IEEE) Institute of Electrical and Electronics Engineers
– (EIA) Electronic Industries Association

Forums
– Created by special-interest groups
– Present their conclusions to the standards bodies
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Regulatory Agencies
– Protect the public by regulating radio, television and wire/cable
communications (FCC – Federal Communications Commission
STANDARDS
Internet Standards
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Tested specification that is useful to be adhered by who use the
Internet
Formalized regulation the must be followed
Specification become Internet standard
– Begins as Internet draft for 6 months
– Upon the recommendation from the Internet authorities draft published as
(RFC) Request for Comment