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Introduction to Computer Networks

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Title: Introduction to Computer Networks


1
REVIEW OF COMPUTER NETWORKS
COURSE
LECTURE 1
COMS 525 TCPIP
TOPIC
K. PALANIVEL Systems Analyst, Computer
Centre Pondicherry University, Puducherry
605014.
2
Internet in a Minute
Department of Computer Science, Pondicherry
University, Puducherry - 605014
3
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
4
Network in India (BSNL)
BSNL Core Router
Department of Computer Science, Pondicherry
University, Puducherry - 605014
5
Network in India (BSNL)
BSNL Core Router
Department of Computer Science, Pondicherry
University, Puducherry - 605014
6
Network in India (BSNL)
BSNL Core Router
Department of Computer Science, Pondicherry
University, Puducherry - 605014
7
Network in India (BSNL)
BSNL Core Network
Department of Computer Science, Pondicherry
University, Puducherry - 605014
8
Network in India (BSNL)
BSNL Core Network
Department of Computer Science, Pondicherry
University, Puducherry - 605014
9
Computer Networking
10
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
11
Networking (Contd.)
  • Computer networks have opened up an entire
    frontier in the world of computing called the
    client/server model

Department of Computer Science, Pondicherry
University, Puducherry - 605014
12
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
13
Types of Networks
14
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
15
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
16
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
17
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
18
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
19
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
20
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.
Department of Computer Science, Pondicherry
University, Puducherry - 605014
21
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
22
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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University, Puducherry - 605014
23
Sample LAN Implementation
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24
Topology
25
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
26
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
27
Types of Topology
  • A bus technology called Ethernet has become the
    industry standard for local-area networks

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University, Puducherry - 605014
28
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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University, Puducherry - 605014
29
Star
  • A star network is designed with each node (file
    server, workstation, peripheral) connected
    directly to a central network hub or server

Department of Computer Science, Pondicherry
University, Puducherry - 605014
30
Ring
  • A ring network is one where all workstations and
    other devices are connected in a continuous loop.
    There is no central server

Department of Computer Science, Pondicherry
University, Puducherry - 605014
31
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

Department of Computer Science, Pondicherry
University, Puducherry - 605014
32
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
33
Sending a packet from One Location to Another
34
Sending a packet from Argon to Neon
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35
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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University, Puducherry - 605014
36
Communications Architecture
37
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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University, Puducherry - 605014
38
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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University, Puducherry - 605014
39
OSI Reference Model 7 Layers
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40
OSI Reference Model 7 Layers
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41
OSI Reference Model 7 Layers
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42
OSI Reference Model Packet Movement
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43
OSI Reference Model Protocols
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44
OSI Reference Model Protocols
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45
OSI Reference Model Protocols
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46
OSI Reference Model Protocols
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47
OSI Reference Model LAN to WAN
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48
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
49
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
50
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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University, Puducherry - 605014
51
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
52
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
53
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
54
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).

Department of Computer Science, Pondicherry
University, Puducherry - 605014
55
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.

Department of Computer Science, Pondicherry
University, Puducherry - 605014
56
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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University, Puducherry - 605014
57
Data Encapsulation
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58
OSI Vs TCP/IP
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59
OSI Vs TCP/IP
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60
Network Devices
61
Data Transmission Via UTP
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Data Transmission Via Devices
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63
Data Transmission Via UTP Cables
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64
Data Transmission Via Wirless Devices
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65
Data Transmission Via Wireless Devices
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66
Data Transmission Via Wireless Devices
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University, Puducherry - 605014
67
Network Devices Hub
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68
Network Devices Switch
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69
Network Devices Switch
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70
Network Devices Router
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71
Network Devices Router
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72
Network Devices Router
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73
Network Devices Router
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74
Communication Satellite
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75
Communication Mobile
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76
Communication Satellite
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University, Puducherry - 605014
77
  • Questions?

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University, Puducherry - 605014
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Review
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University, Puducherry - 605014
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