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Computer Networks and the Internet

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Computer Networks and the Internet CMPT 109 Montclair State University – PowerPoint PPT presentation

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Title: Computer Networks and the Internet


1
Computer Networksand the Internet
  • CMPT 109
  • Montclair State University

2
Computer Data Communication
  • Computer Data communications involves
    transmitting information on the form of coded bit
    patterns over appropriate channels.
  • Download The action of retrieving data into your
    computer.
  • Upload The action of sending data into another
    computer (you need privileges to access the other
    computer).

3
Data Communication
  • Data Communication can be established using
    analog or digital signal.
  • Analog signal is a continuous wave pattern. The
    telephone system uses analog signals
  • Digital signal consists of a series of 1s and 0s.
    HDTV uses digital signals.
  • Signal can be of any kind Electric current,
    electromagnetic waves, light pulses, etc.

4
Telephone Network Circuit Switching
  • When you make a telephone call
  • The telephone switching system creates an
    electrical circuit between two telephones
  • The switching system maintains this circuit until
    you hang up.

5
Circuit Switching (continued)
  • Appropriate for telephone networks
  • Analog data is degraded at each station
  • Telephone conversations require relatively
    continuous flow of data across circuit
  • Not appropriate for computer networks
  • Digital data does not degrade at links, so more
    intermediate nodes are possible.
  • Computers generate data in bursts, with long
    intervening periods of silence, wasting
    bandwidth

6
Computer Networks
  • It normally consists of tow or more independent
    computer connected together with communication
    links and equipment, to share resources
  • There are two types of networks WAN (Wide Area
    Network) and LAN (Local Area Network).
  • WANs may span great geographic distances.
  • LANs connect computers located not far away.

7
Computer Networks
  • WANs share software and information
  • LANs share devices, software and information
  • The communication links are full-duplex, i.e both
    computers can communicate simultaneously. A
    half-duplex communication only allows one
    computer to transmit at any given time.

8
Computer Networks Packet Switching
  • Connect computers in a network, often with
    redundant links. Each computer is a node in the
    network.
  • Source computer splits message into one or more
    packets, each with part of message.
  • Each packet also contains address of destination
    computer.
  • Source computer sends packets to an adjacent node
    in the network.

9
Packet Switching (continued)
  • When a networked computer receives a packet, it
    examines the packets address.
  • If the computer is not the packets final
    destination, it forwards the packet to an
    adjacent node thats closer to the packets
    destination.
  • The destination computer collects the packets and
    re-assembles them into the original message.

10
Packet Switching Illustration
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HELP (to 8)
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11
Some Remarks about Packet Switching
  • Not all the packets in a message need to take the
    same route between source and destination.
  • The packets in the message do not need to arrive
    at the destination in proper order.
  • Messages transmitted via a packet-switched
    network are inherently vulnerable to unauthorized
    interception.

12
Network Protocols
  • A protocol is a set of rules for exchange of data
    among two or more parties (e.g., among computers
    in a network).
  • A packet-switched network protocol needs to
    specify the following (at a minimum)
  • The structure of a packet
  • Format for source and destination address
  • Routing of packets through the network
  • Splitting and reassembling of messages

13
Types of Protocols
  • A general communication protocol often contains
    specific protocols for different types of
    messages.
  • For example, there may be protocols for
  • Remote logins
  • Transfer (actually copying) of data files
  • E-mail messages

14
WANs
  • They need hardware to connect the computers. It
    could be a modem and the POTS, or a modem and a
    ADSL connection.
  • They also need software to synchronize the
    transmission of the data between the two
    computers.

15
LANs
  • They need hardware to connect the computers A
    NIC (Network Interface Card), and some type of
    cabling (twisted pair, coaxial, fiber optic).
  • They also need the software, that must
    correspond to the network topology that is being
    used.

16
Network Topologies
  • A topology is the physical arrangement of the
    computers in a network
  • In a star topology, each computer is linked to a
    central computer.
  • In a ring topology, the computers are arranged in
    a circle.
  • In a bus topology, computers (or sub-networks)
    are linked to a backbone.
  • In a mesh topology, computers a linked in a
    (rectangular) grid.

17
A Star Topology
Client
Client
Client
Server
Client
Client
Client
18
A Ring Topology
Node
Node
Node
Messages are passed in this direction
Node
Node
Node
Node
Node
19
A Bus Topology
Node
Node
Node
Node
Node
Node
Server
Node
Node
Backbone
Node
Node
Node
Node
Server
Node
20
Mesh Topology
Node
Node
Node
Node
Node
Node
Node
Node
Node
Node
Node
Node
21
MSUs Local Area Network
  • Essentially a bus topology, with several
    sub-networks. Machines communicate using the
    Ethernet protocol.
  • The PCs in RI 105 and RI 108 -- together with the
    server in RI 109 -- form one sub-network. The
    PCs are clients.
  • Most of the other PCs on campus are parts of
    different sub-networks

22
The Internet
  • The Internet is really a network of networks,
    with no specified topology.
  • The LAN at MSU is one of the networks in the
    Internet.
  • The protocol for communication over the Internet
    is TCP/IP (Transmission Control Protocol/Internet
    Protocol).

23
Internet Protocols
  • telnet -- allows remote logins
  • ftp -- file transfer protocol
  • mailto -- protocol for sending e-mail
  • http -- hypertext transfer protocol. This
    protocol makes the World Wide Web possible.

24
The World Wide Web
  • The part of the Internet that uses hypertext.
  • Web pages written in hypertext markup language
    (HTML) may contain embedded hypertext links to
    other pages. This other page may be anywhere on
    the Internet.
  • A hypertext link to a page makes use of that
    pages Uniform Resource Locator (URL).

25
WWW (continued)
  • A web browser is a program that allows one to
    view documents written in HTML and to traverse
    the embedded hypertext links.
  • The two major web browsers are Netscape Navigator
    and Microsofts Internet Explorer. Other
    browsers exist (e.g. Lynx).
  • Hypertext links allow one to access information
    without having to know its physical location.
  • Instead, the URL for the physical location is
    embedded in the HTML document.
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