DATA COMMUNICATION

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Computer Networks Introduction Zaka
Ul-Mustafa Zaka-mcs_at_nust.edu.pk Faculty
offices, Old telecom building. Office timings
During Student Teacher Interaction
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Text Book

• Computer Networks (Fourth edition)
• By Andrew S. Tanenbaum
• Data Communication and Networking by Fourouzan
• For reference books, see course handout.

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Course Goals

• Fundamental understanding of the network
  architecture and how to provide application
  requirements
• Cover core as well as newer networking
  technologies
• Goal is to cover as much breadth rather than
  depth
• As much hands on experience as possible
• Quantitative approach
• Home work projects should help

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Course policies

• Course organization and expectation
• Grading policy
• Final 50
• Midterm 30
• Quizzes Assignments 20
• late policy
• None Projects/homework/critiques are due at
  right before the beginning of class. I do not
  accept late submissions.
• Please contact me regarding unforeseen
  emergencies
• Academic honesty
• Plagiarism may not be tolerated.

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DATA COMMUNICATION

• Communication and Telecommunication.
• Data Communication---------- Exchange of 0s and
  1s.
• Data Communication --------- Local Remote
• Effective Data Communication (Fundamental
  characteristics)
• a) Delivery-------- correct destination
• b) Accuracy------- correct data
• c) Timeliness----- Same order No significant
  delay

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Block Diagram of a communication System
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Components

• Data or Massage
• Sender
• Receiver
• Link or Medium or communication Channel
• Protocol

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Network Applications

• Marketing and Sales
• Financial Services
• Manufacturing
• Electronic Messaging
• Directory Services
• Information Services
• Electronic Data Interchange
• Teleconferencing
• Cellular TelePhone
• Cable Television

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Uses of Computer Networks

• Business Applications
• Home Applications
• Mobile Users
• Social Issues

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Business Applications of Networks

• A network with two clients and one server.
• Resource Sharing Client Server Model

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Business Applications of Networks (2)

• The client-server model involves requests and
  replies.

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• Strong Communication. Emails, video conferencing
• Manufacturing Processes
• Inventory control
• E-commerce

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Home Network Applications

• Access to remote information (hobbies,
  newspapers)
• Person-to-person communication
• Interactive entertainment
• Electronic commerce

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• Mobile user
• Social issues (e.g privacy issues,)

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Home Network Applications (3)

• Some forms of e-commerce.

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PROTOCOLS

• Merely sending the bit stream from one node to
  another and expecting a proper communication to
  occur !
• Life is not that simple!!!
• Protocol defines What is communicated how it is
  communicated and When it is communicated.

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STANDARDS

• There are many factors needed to be synchronized.
• Why standards are necessary?(Competitive Market)
• Two types of standards
• a) De facto (By Fact)
• b)De Jure (By Law)
• i) Proprietary (closed standards)
• ii) Nonproprietary (Open standardsDeveloped
  by groups or committees)

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De Jure Standards

• De jure standards are those ratified by
  recognized international standards bodies such as
  the ISO and IEEE. Ethernet is an example of a de
  jure standard

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De facto standards

• de facto standards usually result from a
  standards battle in the market where dominance is
  achieved by being first, being bigger, being
  better or having more marketing clout. But
  standards battles can also be won by second to
  market, smaller, inferior products and standards.
  The Sony Playstation was second to market after
  Sega
• Those which arent necessarily open or based on
  any de jure standards. DOS is an example of a de
  facto standard.     At a time when it mattered,
  there were three distinct DOS products on the
  market MS-DOS from Microsoft, PC DOS from IBM,
  and DR DOS from Digital Research. Although they
  were similar products with similar features, each
  had its own quirks which meant you could never be
  100 per cent certain your software would run on
  them all.   

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Standards and Organizations

• Standards are developed by cooperation between
  Standards Creation committees, forums and
  government agencies
• Standards Creation Committees
• a) ISO(International standards
  Organization,1947,82 members)
• Provides models for Compatibility, improved
  Quality, increased productivity decreased prices)
• b) ITU-T (International Telecommunication
  Union-Telecommunication Standards Sector)
• United nation developed CCIIT.
• Two popular standards developed by ITU are
  V series and X series.
• c) IEEE
• It sponsored an important project for local
  area network called Project 802

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Forums

• To accommodate the need of working models,
  agreements and to facilitate the process of
  standardization.
• Forum works with universities and users to test
  evaluate and standardize new technologies.
• Internet Society (ISOC) and Internet Engineering
  Task Force(IETF)
• ISOC concentrates on user issues, including
  enhancement to the TCP/IP protocol suit.
• IETF reviewa internet software and hardware.
• e.g SNMP (Simple Network Management Protocol)

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Regulatory Agencies

• All communication Technologies require approval
  from Government Agencies
• The purpose of these agencies is to protect
  people interest by regulating radio and Wireless
  communication
• IN Pakistan PTA (Pakistan Telecom Authority)
• In America FCC

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Network Hardware

• Local Area Networks
• Metropolitan Area Networks
• Wide Area Networks
• Wireless Networks
• Home Networks
• Internetworks

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Broadcast Networks

• Types of transmission technology
• Broadcast links
• Point-to-point links

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Metropolitan Area Networks

• A metropolitan area network based on cable TV.

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Wide Area Networks

• Relation between hosts on LANs and the subnet.

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Wide Area Networks (2)

• A stream of packets from sender to receiver.

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Broadcast Networks

• Types of transmission technology
• Broadcast links
• By a specific bit pattern in address field
• Multicast, one bit for indicating multicast
  transmission other n-1 bits for group address.
• Point-to-point links
• Also called Unicasting

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Broadcast Networks (2)

• Classification of interconnected processors by
  scale.

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Types of Networks

• There are three different ways in which we
  classify the networks
• Organizational Point of View
• Geographical Point of View
• Computing Point of View

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Organizational Point of View

• From organizational point of view, networks are
  divided into two types
• Peer-to-Peer
• Server based

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Peer-to-Peer

• These are also called Workgroups.
• A peer-to-peer network comprises of 10 or less
  users and is suitable for small-sized business
  organizations.
• In this model of networking the resources are
  randomly scattered on the network with every
  machine acting as a server as well as client

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Server Based networks

• They are sometimes referred to as Domains.
• This is a centralized model of networking with
  resources placed on a dedicated machine called
  Server.
• There is no user limit as such, as it depends
  directly on your hardware resources and capacity
  to support users.

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Geographical Point of View

• From geographical point of view, there are three
  types of networks.
• LAN
• WAN
• MAN/CAN

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LAN or Local Area Network

• A LAN encompasses a small area such as a floor or
  a building with all the machines connected
  directly via the same medium generally.

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• LANs may be characterized by
• their size
• Their transmission technology
• Their topology

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Local Area Networks

• Arbitration may be centralized or distributed

• Channel allocation may be static (e.g round
  robin) or dynamic (centralized or decentralized).

• Two broadcast networks
• (a) Bus
• (b) Ring

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Local Area Network
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Some more topologies

• Mesh
• How many cables and I/O ports are needed?
• Advantages disadvantages
• Star
• Hub. As a repeater, active Hubs, passive
  Hubs.
• Advantages
• Less cables as compared to ?
• In case of a single link failure
• Easy Fault Identification
• Disadvantages
• Reletively more cables .
• Tree topology
• Hybrid topology.

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Mesh topology
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WAN or Wide Area Network

• A WAN comprises of a very large physical area
  that covers countries and continents. Internet is
  one good example of a WAN. The machines in a WAN
  are connected through different mediums and
  protocols. Generally, the Dial-up-Networks are
  used for this purpose.

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Wide Area Network
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Wide Area Networks

• Relation between hosts on LANs and the subnet.

• Host Machines for running user programs.

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Wide Area Networks (2)

• A stream of packets from sender to receiver.

• STORE FORWARD

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MAN (Metropolitan Area Network)or CAN (Campus
Area Network)
A MAN is almost similar to a WAN except that a
MAN only encompasses an area that is within a
city. CAN is a campus area Network which is used
with in a campus for the sharing of resources.
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Computing Point of View

• Networks are divided into two types from the
  point of view of computing.
• Centralized Networks
• Client-Server Networks

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Centralized Networks

• The centralized networks rely totally on one
  dedicated machine called server for all the
  processing and computing and the clients or the
  terminals act as dumb entities.
• If the client requires a certain set of data,
  whole of the data set is transferred at the
  client end, which also is wastage of the network
  bandwidth.

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Client-Server Networks

• In this model of networking, only the required
  set of data is returned to the client while both
  the server and the client take part in the
  processing or computing of the queries.
• This is a more efficient way of processing and is
  hence applied generally more than the centralized
  method, nowadays. .

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Wireless Networks (2)

• (a) Bluetooth configuration
• (b) Wireless LAN

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Wireless Networks (3)

• (a) Individual mobile computers
• (b) A flying LAN

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Network Software

• Layers . To reduce complexity
• Shielding, data encapsulation
• Peer layers
• Protocol. The agreement between layers and
  parties.
• Interfaces
• No data is directly communicated between two
  layers
• Protocol stack
• Network architecture. Set of layers and
  protocols.

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Dessign issues

• Addressing
• Error control
• Flow control
• Multiplexing
• Routing