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Computer Network

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Computer Network What is a Network? A computer Network is a set of two or more interconnected computers and a set of hardware devices. Need for Networking Resource ... – PowerPoint PPT presentation

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Title: Computer Network


1
Computer Network
2
  • What is a Network?
  • A computer Network is a set of two or more
    interconnected computers and a set of hardware
    devices.
  • Need for Networking
  • Resource Sharing
  • Reliability
  • Cost Factor
  • Communication medium
  • Application of Network
  • Sharing Peripherals and data sharing
  • Access to remote database

3
  • Communication facilities
  • Elementary Terminology of Networks
  • Nodes (Workstations) - Nodes refers to the
    computer that are attached to a network
  • Server A computer that facilitates the sharing
    of data, software and hardware resources (e.g.
    Printer, modem etc) on the network is termed as a
    server.
  • Server is of two types
  • Non Dedicated Server 2- Dedicated Server
  • Non Dedicated Server - The Server serves both as
    a workstations and server. Such Network is known
    as peer- to peer network
  • Dedicated Server - On bigger network a computer
    is reserved for servers job and its only job is
    to help workstation access data , software and
    hardware. The network using such a server are
    known as Master- Slave networks

4
  • Network Interface Unit NIU(MAC Address)
  • A Network Interface Unit is an interpreter
    that helps establish communication between the
    server and workstation.
  • A unique number identifying workstations
    attached is known as node address
  • NIU is otherwise called TAP (Terminal Access
    Point) or otherwise Network Interface Card NIC
  • MAC (Media Access Control) Refers to the physical
    address assigned by NIC manufacturer. MAC address
    is a 6-byte address of which first 3 are the
    manufacturer-id and last 3 bytes are the card
    no.
  • IP Address Every machine on a TCP/IP network
    has a unique identifying number called IP Address

5
  • Domain Name - It is a unique name assigned to a
    website. It contains three parts www, name
    describing the websites purpose and TLD(Top
    Level Domain) Such as .com,.net, .org .in etc.
  • Domain names are internally converted into
    IP Address before a communication can happen.
  • Domain Name Resolution refers to the process of
    obtaining corresponding IP address from a domain
    name.

6
  • NETWORK TOPOLOGIES
  • The pattern of interconnection of nodes in a
    network is called the Topology
  • Factors to consider in choosing the Topology
  • Cost
  • Flexibility
  • Reliability
  • Types of Topologies
  • Point to- point Link
  • The main characteristic of P-P network is that
    each station receives exactly from one
    transmitter and each transmitter transmits to
    exactly one receiver.

7
  • The Star Topology

8
  • This topology consists of a central node to which
    all other nodes are connected by a single path.
    The star topology has found extensive application
    in area where intelligence in the network is
    concentrated at the central node.
  • Advantages Ease of service, One device per
    connection, Centralized control/Problem diagnosis
    and Simple access protocol.
  • Disadvantages Long cable length , Difficult to
    expand and Central node dependency

9
The bus or linear Topology
10
  • The simplest form of a physical bus topology
    consists of a trunk (main) cable with only two
    end points. When the trunk cable is installed, it
    is run from area to area and device to
    deviceclose enough to each device so that all
    devices can be connected to it with short drop
    cables and T-connectors.
  • The principal advantage of this topology is cost
    no hubs are required, and shorter lengths of
    cable can be used. It is also easy to expand.
    This simple "one wire, two ends" physical bus
    topology is illustrated in Figure
  • Disadvantage Fault diagnosis is difficult,Fault
    isolation is difficult, Repeater Configuration.

11
The Ring or Circular Topology
12
  • It is a closed network structure in the form of
    a circle, to which all nodes are connected. The
    ring name comes from the design of the central
    network device, which has a loop inside it to
    which are attached cables for all the devices on
    the network. MAU(Media Access Unit).

13
The Tree Topology
14
  • A variation of bus topology is tree topology. It
    is also called a "hierarchical" topology, tree
    topology is a combination of bus and star
    topologies. Nodes are connected in groups of
    star-configured workstations that branch out from
    a single "root". The root node usually controls
    the network and sometimes network traffic flow.

15
Graph Topology
16
  • The nodes are connected together in an arbitrary
    fashion. A link may or may not connect two or
    more nodes. There may be multiple links also.

17
Mesh Topology
18
  • Mesh networking is a type of networking wherein
    each node in the network may act as an
    independent router, regardless of whether it is
    connected to another network or not. It allows
    for continuous connections and reconfiguration
    around broken or blocked paths by hopping from
    node to node until the destination is reached. A
    mesh network whose nodes are all connected to
    each other is a Fully connected
  • The primary advantage of this topology is that it
    is highly fault tolerant when one node fails,
    traffic can easily be diverted to other nodes.

19
  • Types of Networks
  • Computer Networks are classified on the basis of
    geographical spread, There can be four types of
    Network
  • Local Area Network (LANs)
  • Metropolitian Area Networks (MANs)
  • Wide Area Networks (WANs)
  • Personal Area Network (PANs)

20
  • Local Area Network (LANs)
  • Local Area Networks (LAN) is a number of devices
    (Computers, Printers, Fax) that are connected to
    each other by some form of wiring, within a
    localized area (within building e.g. a school,
    an office etc. ) to share data and resources. A
    LAN enables independent devices to communicate
    directly with each other through direct
    communications.
  • Metropolitan Area Networks(MANs)
  • In a Metropolitan Area Network computer connected
    to each other with in a city to have the
    organization concentric needs. Though the
    distance between the devices is not very large,
    they can have their own cabling plan.

21
  • Wide Area Network(WANs)
  • Wide Area Networks (WAN) is a number of local
    area networks that are connected to form a large,
    logical network without any geographical
    limitation. WANs can be close together
    physically or separated by a large distance.
    WANs can share a large numbers of resources, or
    they can have different big network.The largest
    WAN in exsistence is the Internet.
  • Personal Area Network (PAN)
  • A Personal Area Network refers to a small network
    of communication- capable devices with in a range
    of reachability of an individual person. The
    range is typically up to 10 meters.

22
Comparison LAN and WAN

LAN WAN
Diameter of not more than a few Kilometers A total data rate of at least several mbps Complete ownership by a single organization very low error rates Span entire Countries Data rate less than 1 mbps Owned by multiple organizationComparatively higher error rates
23
TRANSMISSION MEDIA
  • When data is sent across the network it is
    converted into electrical signals. To be sent
    from one location to another, a signal must
    travel along a physical path. The physical path
    that is used to carry a signal between a signal
    transmitter and a signal receiver is called the
    transmission medium. There are two types of
    transmission media guided and unguided.
  • Guided media includes cables. Unguided media
    includes waves through air(microwaves, radiowaves
    and satellites) Basic types of cable for guided
    media is discussed below

24
Twisted Pair Cable
  • Twisted-pair wiring refers to a type of cable
    composed of two (or more) identical wires twisted
    around each other within a plastic sheath. The
    wires are twisted to reduce crosstalk (The
    bleeding of a signal from one wire to another and
    which can corrupt signal and cause network
    errors. This form of signal interference is
    called Crosstalk). There are "shielded" and
    "unshielded" varieties of twisted-pair cables.

25
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26
  • Advantage 1.It is simple.
  • physically flexible.
  • Very inexpensive.
  • Can easily be connected
  • Disadvantage 1.Because of high attenuation it is
    incapable to carry signals for long
  • distance without
    repeaters.
  • 2.Low bandwidth capabilities make it unsuitable
    for broadband applications
  • 3. It support maximum data rate 1 Mbps to 10 Mbps

27
2. Coaxial Cable
  • This type of cable is referred to as coaxial
    because it contains one copper wire (or physical
    data channel) that carries the signal and is
    surrounded by another concentric physical channel
    consisting of a wire mesh or foil. The outer
    channel serves as a ground for electrical
    interference. It is better than twisted pair

28
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29
  • Advantage better than twisted pair,can be used
    for broadband transmission (can be used with
    Cable TV) , bandwidth upto 400 MBPS
  • Disadvantage Expensive compared to twisted pair
    cables , Coaxial is not compatible with twisted
    pair cables.

30
3. Optical Fibers
  • Optical fibers consist of thin strand of glass
    like material which are so constructed that they
    carry light from a source at one end of the fiber
    to a detector at the other end.

31
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32
  • Advantage 1.immune to magnetic interference.
  • 2. Highly suitable for harsh industrial
    environment
  • 3. guarantees secure transmission
  • Disadvantage 1. Installation problem
  • 2. Fiber optic cable are more difficult to
    solder
  • 3. They are the most expensive of all cable

33
  • Unguided Media
  • Microwave and Radiowave
  • Radio Waves are low levels of transmission power
    for signals to and from your phone. These
    non-ionizing frequencies of radiation are safe.
    However as signal strength grows from a few
    hundred MHZ of power to beyond 800 MHZ, the
    electromagnetic spectrum increases and these
    waves become microwaves.

34
  • Advantages
  • It is cheaper then the guided media, and require
    less maintenance.
  • It cover large distance With 100meter high tower
    distance of 100 Km between towers are feasible.
  • Disadvantages
  • It is unsecured medium of communication.
  • The loss of signal is more as compared to guided
    media.
  • Its communication depend up on the atmospheric
    conditions.

35
  • satellite
  • Satellite communication is special case of
    microwave relay system. In satellite
    communication the earth station consists of a
    satellite dish that functions as an antenna and
    communication equipment to transmit and receive
    data from satellite passing over head.
  • Advantage The area covered is quite larger
  • Disadvantage Technological limitations
    preventing the development of larger, high gain
    antennas on the satellite platform

36
  • Infrared
  • This type of transmission is used in TV remotes,
    wireless speakers etc. It transmits data through
    air and can propagate throughout a room.

37
  • Laser
  • The Laser transmission requires direct line of
    sight. It is unidirectional like microwave, but
    has much higher speed than microwave . Laser
    transmission is point to point transmission,
    typically between buildings

38
  • Bluetooth
  • Bluetooth is used to interconnect devices in
    short distance. Bluetooth requires that a
    low-cost transceiver chip be include in each
    device. Mobile phones PDAs can be easily
    interconnected.

39
NETWORK DEVICESModem
40
  • Hub
  • A Hub is a multipurpose network device that lies
    at the centre of a network to channel the traffic
    from one computer to another.
  • Hubs are of two type
  • Active Hub Electrically amplify the signal
  • Passive Hub Allow the signal to pass from one
    computer to another

41
  • Switch
  • A switch is a device that is used to segment
    networks into different subnetworks called
    subnets or LAN segments. Prevents traffic
    overloading in a Network
  • A Switch is responsible for filtering i.e.
    transforming data ina specific way and forwarding
    packets between LAN segment

42
  • Repeater
  • A Repeater is a network device that boosts the
    power of incoming signals to allow the length of
    a network to be extended.

43
  • Gateway
  • A Gateway is a network device that connects
    dissimilar network. It establishes an intelligent
    connection between a local network and external
    networks with completely different structure.

44
  • Bridge
  • A Bridge is a network device capable of
    connecting networks that use similar protocols.
    It connects two local area networks running the
    same network operating system.
  • A bridge allows to cross only that data which has
    valid MAC address of other side of Bridge

45
  • Router
  • A Router is a network device that connects
    multiple networks irrespective of their protocol.
    This is because a router can handle different
    protocol, otherwise it works similar to the
    bridge.
  • A Router forwards data packets from one connected
    network to another depending upon their IP
    address and not their MAC address.

46
NETWORK SECURITY
  • Intrusion Problems/ Access Attacks
  • When an unauthorized user attempts to gain access
    to protected sensitive information, it is known
    as Access Attack or Intrusion Problem.This type
    of attack is an attack against confidentiality of
    information.
  • Snooping refers to unauthorized access of someone
    elses data, email, computer-activity or data
    communication.
  • Eavesropping is the act of secretly listening
    /intercepting someone elses private
    communication/data /information

47
  • Denial of Service (DoS) Attacks
  • Denial of service attacks are those attacks that
    prevent the own users of the system from
    accessing or using resources, information. DoS
    attacks can be of different types-
  • Denial of access to information
  • Denial of access to Applications
  • Denial of access to system
  • Denial of access to Communications

48
NETWORK SECURITY MEASURES
  • Active Protection
  • Authorization
  • Firewall A system designed to prevent
    unauthorized access to or from a private network
    is called firewall
  • Intrusion detection
  • Preventive Measures
  • Implement proper Security Policy for your
    organization
  • Use proper fie access permissions when sharing
    files on the internet
  • Disconnect from the internet when away

49
  • Thank You
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