Introduction to Computer Networks

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REVIEW OF COMPUTER NETWORKS
COURSE
LECTURE 1
COMS 525 TCPIP
TOPIC
K. PALANIVEL Systems Analyst, Computer
Centre Pondicherry University, Puducherry
605014.
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Internet in a Minute
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Internet in a Minute
This is what happens in an internet minute in 2018

• Internet connectivity
• unique ICANN-overseen IP number for duration of
  connection
• ability to exchange general Internet traffic
  (POP, http) with other ICANN-overseen IP addresses

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Network in India (BSNL)
BSNL Core Router
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Network in India (BSNL)
BSNL Core Router
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Network in India (BSNL)
BSNL Core Router
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Network in India (BSNL)
BSNL Core Network
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Network in India (BSNL)
BSNL Core Network
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Computer Networking
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Computer Networking

• Computer Network - A collection of computing
  devices that are connected in various ways in
  order to communicate and share resources
• Usually, the connections between computers in a
  network are made using physical wires or cables
• However, some connections are wireless, using
  radio waves or infrared signals
• The generic term node or host refers to any
  device on a network
• Data transfer rate The speed with which data is
  moved from one place on a network to another
• Data transfer rate is a key issue in computer
  networks

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Networking (Contd.)

• Computer networks have opened up an entire
  frontier in the world of computing called the
  client/server model

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Networking (Contd.)

• File server A computer that stores and manages
  files for multiple users on a network
• Web server A computer dedicated to responding to
  requests (from the browser client) for web pages

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Types of Networks
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Types of Networks

• Local-area network (LAN) A network that
  connects a relatively small number of machines in
  a relatively close geographical area
• A LAN connects network devices over a relatively
  short distance.
• A networked office building, school, or home
  usually contains a single LAN, though sometimes
  one building will contain a few small LANs
  (perhaps one per room), and occasionally a LAN
  will span a group of nearby buildings.
• In addition to operating in a limited space, LANs
  are also typically owned, controlled, and managed
  by a single person or organization.

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Local Area Networks (LAN)

• LANs are confined to a relatively small area such
  as a school or a building
• LANs usually have one computer designated as the
  file server
• Other computers are connected to the network by
  cables connecting network interface cards in each
  computer

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Wireless LANS

• Wireless networks use high frequency radio
  signals to communicate between the workstations
  and the fileserver or hubs.
• Disadvantages of wireless networks are
• they are expensive (relatively),
• provide poor security,
• are susceptible to interference and
• are slower than cabled networks

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Metropolitan-Area Network (MAN)

• MAN - The communication infrastructures that have
  been developed in and around large cities
• A MAN is a large computer network that usually
  spans a city or a large campus.
• A MAN usually interconnects a number of local
  area networks (LANs) using a high-capacity
  backbone technology, such as fiber-optical links,
  and provides up-link services to wide area
  networks (or WAN) and the Internet.

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Wide-Area Network (WAN)

• Wide-area network (WAN) A network that connects
  two or more local-area networks over a
  potentially large geographic distance
• Often one particular node on a LAN is set up to
  serve as a gateway to handle all communication
  going between that LAN and other networks
• Communication between networks is called
  internetworking
• The Internet, as we know it today, is
  essentially the ultimate wide-area network,
  spanning the entire globe

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Wide-Area Network (WAN)

• WANs connect larger areas, such as whole states,
  or even the world.
• Transoceanic cables and satellites are used to
  connect WANs

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LAN vs. WAN
LAN WAN
1.Diameter of not more than a few kilometers. 1.Span entire countries.
2.A total data rate of at least several mbps. 2.Data rate less than 1 mbps.
3.Complete ownership by a single organization. 3.Owned by multiple organization.
4.Very low error rates. 4.Comparitively higher error rates.
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Protocol

• A protocol is a set of rules that governs the
  communications between computers on a network
• These rules include guidelines that regulate the
  method of access, types of cabling and speed of
  data transfer

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The most common protocols are
Protocol a formal description of a set of rules
and conventions that govern how devices on a
network exchange information

• Ethernet
• Local Talk
• Token Ring
• FDDI
• ATM

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Sample LAN Implementation
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Topology
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Topology

• The physical topology of a network refers to the
  configuration of cables, computers and other
  peripherals.
• The main types of network topologies are
• Linear Bus
• Star
• Ring
• Tree or Hybrid

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Types of Networks Topology

• Various configurations, called topologies, have
  been used to administer LANs
• Ring topology A configuration that connects all
  nodes in a closed loop on which messages travel
  in one direction
• Star topology A configuration that centers
  around one node to which all others are connected
  and through which all messages are sent
• Bus topology All nodes are connected to a
  single communication line that carries messages
  in both directions

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Types of Topology

• A bus technology called Ethernet has become the
  industry standard for local-area networks

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Linear Bus

• A linear bus topology consists of a main run of
  cable with a terminator at each end. All servers
  workstations and peripherals are connected to the
  linear cable

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Star

• A star network is designed with each node (file
  server, workstation, peripheral) connected
  directly to a central network hub or server

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Ring

• A ring network is one where all workstations and
  other devices are connected in a continuous loop.
  There is no central server

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Tree or hybrid

• A tree or hybrid topology combines
  characteristics of linear bus and star and/or
  ring topologies.
• It consists of groups of star-configured
  workstations connected to a linear bus backbone
  cable

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Mesh Topology

• In a mesh network topology, each of the network
  node, computer and other devices are
  interconnected with one another.
• Every node not only sends its own signals but
  also relays data from other nodes. in fact a true
  mesh topology is the one where every node is
  connected to every other node in the network.
• This type of topology is very expensive as there
  are many redundant connections, thus it is not
  mostly used in computer networks.

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Sending a packet from One Location to Another
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Sending a packet from Argon to Neon
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Explanation
128.143.71.21 is not on my local
network. Therefore, I need to send the packet to
my default gateway with address 128.143.137.1
128.143.71.21 is on my local network. Therefore,
I can send the packet directly.
frame
frame
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Communications Architecture
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Communications Architecture

• The complexity of the communication task is
  reduced by using multiple protocol layers
• Each protocol is implemented independently
• Each protocol is responsible for a specific
  subtask
• Protocols are grouped in a hierarchy
• A structured set of protocols is called a
  communications architecture or protocol suite

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OSI Reference Model

• The OSI model is now considered the primary
  Architectural model for inter-computer
  communications.
• The OSI model describes how information or data
  makes its way from application programmes (such
  as spreadsheets) through a network medium (such
  as wire) to another application programme located
  on another network.
• The OSI reference model divides the problem of
  moving information between computers over a
  network medium into SEVEN smaller and more
  manageable problems .
• This separation into smaller more manageable
  functions is known as layering.

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OSI Reference Model 7 Layers
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OSI Reference Model 7 Layers
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OSI Reference Model 7 Layers
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OSI Reference Model Packet Movement
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OSI Reference Model Protocols
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OSI Reference Model Protocols
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OSI Reference Model Protocols
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OSI Reference Model Protocols
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OSI Reference Model LAN to WAN
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OSI A Layered Network Model

• The process of breaking up the functions or tasks
  of networking into layers reduces complexity.
• Each layer provides a service to the layer above
  it in the protocol specification.
• Each layer communicates with the same layers
  software or hardware on other computers.
• The lower 4 layers (transport, network, data link
  and physical Layers 4, 3, 2, and 1) are
  concerned with the flow of data from end to end
  through the network.
• The upper four layers of the OSI model
  (application, presentation and sessionLayers 7,
  6 and 5) are orientated more toward services to
  the applications.
• Data is Encapsulated with the necessary protocol
  information as it moves down the layers before
  network transit.

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Physical Layer

• Provides physical interface for transmission of
  information.
• Defines rules by which bits are passed from one
  system to another on a physical communication
  medium.
• Covers all - mechanical, electrical, functional
  and procedural - aspects for physical
  communication.
• Such characteristics as voltage levels, timing of
  voltage changes, physical data rates, maximum
  transmission distances, physical connectors, and
  other similar attributes are defined by physical
  layer specifications.

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Data Link Layer

• Data link layer attempts to provide reliable
  communication over the physical layer interface.
• Breaks the outgoing data into frames and
  reassemble the received frames.
• Create and detect frame boundaries.
• Handle errors by implementing an acknowledgement
  and retransmission scheme.
• Implement flow control.
• Supports points-to-point as well as broadcast
  communication.
• Supports simplex, half-duplex or full-duplex
  communication.

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Network Layer

• Implements routing of frames (packets) through
  the network.
• Defines the most optimum path the packet should
  take from the source to the destination
• Defines logical addressing so that any endpoint
  can be identified.
• Handles congestion in the network.
• Facilitates interconnection between heterogeneous
  networks (Internetworking).
• The network layer also defines how to fragment a
  packet into smaller packets to accommodate
  different media.

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Transport Layer

• Purpose of this layer is to provide a reliable
  mechanism for the exchange of data between two
  processes in different computers.
• Ensures that the data units are delivered error
  free.
• Ensures that data units are delivered in
  sequence.
• Ensures that there is no loss or duplication of
  data units.
• Provides connectionless or connection oriented
  service.
• Provides for the connection management.
• Multiplex multiple connection over a single
  channel.

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Session Layer

• Session layer provides mechanism for controlling
  the dialogue between the two end systems. It
  defines how to start, control and end
  conversations (called sessions) between
  applications.
• This layer requests for a logical connection to
  be established on an end-users request.
• Any necessary log-on or password validation is
  also handled by this layer.
• Session layer is also responsible for terminating
  the connection.
• This layer provides services like dialogue
  discipline which can be full duplex or half
  duplex.
• Session layer can also provide check-pointing
  mechanism such that if a failure of some sort
  occurs between checkpoints, all data can be
  retransmitted from the last checkpoint.

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Presentation Layer

• Presentation layer defines the format in which
  the data is to be exchanged between the two
  communicating entities.
• Also handles data compression and data encryption
  (cryptography).

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Application Layer

• Application layer interacts with application
  programs and is the highest level of OSI model.
• Application layer contains management functions
  to support distributed applications.
• Examples of application layer are applications
  such as file transfer, electronic mail, remote
  login etc.

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OSI in Action

• A message begins at the top application layer and
  moves down the OSI layers to the bottom physical
  layer.
• As the message descends, each successive OSI
  model layer adds a header to it.
• A header is layer-specific information that
  basically explains what functions the layer
  carried out.
• Conversely, at the receiving end, headers are
  striped from the message as it travels up the
  corresponding layers.

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Data Encapsulation
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OSI Vs TCP/IP
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OSI Vs TCP/IP
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Network Devices
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Data Transmission Via UTP
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Data Transmission Via Devices
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Data Transmission Via UTP Cables
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Data Transmission Via Wirless Devices
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Data Transmission Via Wireless Devices
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Data Transmission Via Wireless Devices
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Network Devices Hub
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Network Devices Switch
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Network Devices Switch
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Network Devices Router
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Network Devices Router
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Network Devices Router
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Network Devices Router
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Communication Satellite
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Communication Mobile
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Communication Satellite
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• Questions?

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Review
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