Transcript Document

Information technology
Lecture 4: Information
Networks (40 slides)
Lecturer:
Prof. Anatoly Sachenko
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Lecture Overview
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LAN and WAN
Topologies and Architectures of Computer
Networks
Intranet and Extranet
The Internet
The Telephone Network in Computing
Data Transfer
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Modem
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LAN and WAN
A
local area network (LAN) is a computer network
covering a small geographic area, like a home, office,
or group of buildings
It
allows to share the memory, printers,
applications and files across a network
It extends for a few km
 The
defining characteristics of LAN, in contrast to
Wide Area Network (WAN), include:
their much higher data transfer rates
 smaller geographic range
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WAN
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Wide Area Network (WAN) is a computer network that
covers a broad area (i.e., any network whose
communications links cross metropolitan, regional,
or national boundaries)
The largest and most well-known example
of a WAN is the Internet
 WANs are used to connect LANs and other
types of networks together (see next slide)
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so that users and computers in one location
can communicate with users and computers in
other locations
Many WANs are built for one particular
organization and are private
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LAN and WAN Illustrations
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LAN and WAN – Client/Server
A
client is an application or system that accesses a (remote)
service on another computer system known as a server by way
of a network
 A server is an application or device that performs services for
connected clients as part of a client-server architecture
 A server computer (often called server for short) is a
computer system that has been designated for running a
specific server application
 Client-server is a computing architecture which separates a
client from a server, and is almost always implemented over
a computer network
 Each client or server connected to a network can also be
referred to as a node (continued on the next slide)
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LAN and WAN - Client/Server
(continued)
The most basic type of client-server architecture
employs only two types of nodes: clients and
servers
 This type of architecture is sometimes referred to
as two-tier
 It allows devices to share files and resources
 Protocol is a convention or standard that controls or
enables the connection, communication, and data
transfer between two computing endpoints
 In its simplest form, a protocol can be defined as
the rules governing the syntax, semantics, and
synchronization of communication
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LAN and WAN – Group Working
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LAN and WAN have applications, which use clientserver technology and orient for group working of
network users
 Printer sharing enable network users to use
network printer, which is connected to the
network in direct way or by means of server
computer
 File sharing enable to access and transfer files
between computers of network
 Application sharing is an element of remote access
that enables network users to access a shared
application or document from their respective
computers simultaneously in real time
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Topologies of Computer Networks
 Topology - logical and physical methods of computers
connection, cables and other components, on the whole
constituent network
A topology characterises networks properties, not
depending on their sizes
Linear
Star
Ring
Cellular
Treelike
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Architectures of Computer Networks –
Ethernet and Token Ring
 Ethernet
is a broadcast network
 It
means that all stations can adopt all
reports
 Its topology is linear
 Its data rate is 10 or 100 Mbit/s
 It’s a most popular network at present
 Token
 Its
Ring is a ring network
principle of data communication is based
on feature, that every site of ring expects
arrival of some short unique bits
sequence— marker, — from a contiguous
previous site
 Data rate 4 or 16 Mbit/s
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Architectures of Computer Networks FDDI
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FDDI (Fiber Distributed Data Interface) is network
architecture of high speed data communication on
fiber lines
Its transmission speed— 100 Mbit/s
 A topology is a double ring or mixed (with
including star-shaped or treelike subnet)
 A maximal amount of the stations is in a
network — 1000
 It has a vulnerable design and expensive
cost of equipment
 It’s used for a long distance
communication, or local application
providing data transfer of high speed
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Architectures of Computer Networks –
Wireless Networks
 Wireless
networks are used wherein the gasket of
cables is laboured, inadvisable or simply impossible
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If network will be implemented through
radio-adapters, and using as data passing
environment radio waves, such network
will be implemented according to the
topology “One connects to all” and
capable of working at distance 50–200 m
Access point - device for connecting
between wireless and cable parts of
network
It is possible to use an ordinary computer
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Architectures of Computer Networks –
Wireless Networks (continued)
 Other
important application of wireless networks
domain is connection organisation between the remote
segments of local networks in default data
communication infrastructure (general access cable
networks, high-quality public-call lines and other)
 In this case for aiming of wireless bridges between
two remote segments radio-bridges are used with
by aerial of the directed type
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Intranet - Definitions
 An
Intranet is a network inside an organization that
uses Internet technologies to provide an Internet-like
environment within the enterprise for information
sharing, communications, collaboration, and the
support of business processes
HTTP and
other Internet protocols are
commonly used as well, such as FTP
 An
Intranet is protected by security measures such
as passwords, encryption, and firewalls, and thus
can be accessed by authorized users through the
Internet
(continued on the next slide)
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Intranet - Illustration
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Extranet
 An
extranet is a private network
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An extranet can be viewed as part of a company's
Intranet that is extended to users outside the
company
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It uses Internet protocols, network connectivity, and
possibly the public telecommunication system to
securely share part of an organization's information
or operations with suppliers, vendors, partners,
customers or other businesses
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Extranet (continued)
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The Internet
 The
Internet is a worldwide, publicly accessible series
of interconnected computer networks that transmit
data by packet switching using the standard Internet
Protocol (IP)
 It is a "network of networks" that consists of
millions of smaller domestic, academic, business,
and government networks, which together carry
various information and services
 Such as electronic mail, online chat, file
transfer, and the interlinked Web pages and
other documents of the World Wide Web
(continued on the next slide)
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The Internet Protocols
 Aside
from the complex physical connections that
make up its infrastructure, the Internet is facilitated
by bi- or multi-lateral commercial contracts and by
technical specifications or protocols that describe how
to exchange data over the network
 Indeed, the Internet is essentially defined by its
interconnections and routing policies
 There are three layers of Internet protocols:
 At the lower level is IP (Internet Protocol), which
defines the datagrams or packets that carry blocks
of data from one node to another
(continued on the next slide)
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The Internet Protocols (continued)
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TCP (Transmission Control Protocol) and UDP (User
Datagram Protocol) exist at the next layer up; these
are the protocols by which data is transmitted
 TCP makes a virtual 'connection', which gives
some level of guarantee of reliability.
 UDP is a best-effort, connectionless transport, in
which data packets that are lost in transit will not
be re-sent
The application protocols sit on top of TCP and UDP
 It defines the specific messages and data formats
sent and understood by the applications running at
each end of the communication
 Examples of these protocols are HTTP (Hypertext
Transfer Protocol), FTP, and SMTP (Simple Mail
Transfer Protocol)
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The Internet Uses
 The
Internet has many common uses
 E-mail. The concept of sending electronic text messages
between parties in a way analogous to mailing letters
or predates the creation of the Internet
 Remote access. The Internet allows computer users to
connect to other computers and information stores
easily, wherever they may be across the world
 File sharing.
 A computer file can be e-mailed to customers,
colleagues and friends as an attachment
(continued on the next slide)
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The Internet Uses (continued)
It can be uploaded to a Web site or FTP server for
easy download by others
 It can be put into a "shared location" or onto a file
server for instant use by colleagues
 The load of bulk downloads to many users can be
eased by the use of "mirror" servers or peer-topeer networks
 Streaming media. Many existing radio and television
broadcasters provide Internet 'feeds' of their live audio
and video streams (for example, the BBC and Rush
Limbaugh)
(continued on the next slide)
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The Internet Uses (continued)
They may also allow time-shift viewing or listening
such as Preview, Classic Clips and Listen Again
features
 An Internet-connected device, such as a computer
or something more specific, can be used to access
on-line media in much the same way as was
previously possible only with a television or radio
receiver
Voice telephony (VoIP). Voice over Internet Protocol,
also called VoIP , IP Telephony, Internet telephony, is
the routing of voice conversations over the Internet or
through any other IP-based network
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The Internet - World Wide Web
 The
World Wide Web (commonly shortened to the Web)
is a system of interlinked, hypertext documents
accessed via the Internet
 With a web browser, a user views web pages that
may contain text, images, videos, and other
multimedia and navigates between them using
hyperlinks
 The World Wide Web was created in 1989 by Sir
Tim Berners-Lee and Sir Sam Walker from the
United Kingdom, and Robert Cailliau from
Belgium, working at CERN in Geneva,
Switzerland
(continued on the next slide)
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World Wide Web (continued)
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Viewing a web page on the World Wide Web
normally begins either by typing the URL (Uniform
Resource Locator) of the page into a web browser,
or by following a hypertext link to that page or
resource
The web browser then begins a series of
communications, behind the scenes, in order to fetch
and display it
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World Wide Web Illustration
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The Telephone Network in Computing Public Switched Telephone Network
 The
public switched telephone network (PSTN) is the
network of the world's public circuit-switched phone
networks, in much the same way that the Internet is the
network of the world's public IP-based packetswitched networks
 Originally a network of fixed-line analog phone
systems, the PSTN is now almost entirely digital,
and now includes mobile as well as fixed phones
 The PSTN is largely governed by technical
standards created by the ITU-T (International
Telecommunication Union)
 It uses E.163/E.164 addresses (known more
commonly as phone numbers) for addressing
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The Telephone Network in ComputingISDN
 Integrated
Services Digital Network (ISDN) is a circuitswitched telephone network system
 It’s designed to allow digital transmission of voice
and data over ordinary telephone copper wires,
resulting in better quality and higher data speeds
than are available with analog
 More broadly, ISDN is a set of protocols for
establishing and breaking circuit switched
connections, and for advanced call features for the
user
 It was invented by Prof. Jaxin Hall of Sussex, UK in
the late 1980's
(continued on the next slide)
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The Telephone Network in ComputingISDN (continued)
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In a videoconference, ISDN provides simultaneous
voice, video, and text transmission between
individual desktop videoconferencing systems and
group (room) videoconferencing systems
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The purpose of the ISDN is to provide fully
integrated digital services to the user
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These services fall under three categories:
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bearer services, supplementary services and
teleservices
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The Telephone Network in Computing –
ISDN Illustration
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The Telephone Network in Computing ADSL
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Asymmetric Digital Subscriber Line (ADSL) is a form
of data communications technology that enables
faster data transmission over copper phone lines
than a conventional voiceband modem can provide
 It
does this by utilizing frequencies that
are not used by a voice telephone call
 A splitter allows a single phone connection
to be used for both ADSL service and voice
calls at the same time
 Because phone lines vary in quality it can
be used generally over short distances only
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Data Transfer- Analog and Discrete Signals
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An analog or analogue signal is any time continuous
signal where some time varying feature of the signal
is a representation of some other time varying
quantity
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A discrete signal or discrete-time signal is a time series,
perhaps a signal that has been sampled from a
continuous-time signal
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Unlike a continuous-time signal, a discrete-time signal
is not a function of a continuous-time argument
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It’s is a sequence of quantities and each value in
the sequence is called a sample
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Data Transfer – Digital Signals
A
digital signal is a discrete-time signal that takes on
only a discrete set of values
It typically derives from a discrete signal
that has been quantized
 Quantization is the process of
approximating a continuous range of
values by a relatively-small set of discrete
symbols or integer values
 Common practical digital signals are
represented as
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8-bit (256 levels), 16-bit (65,536 levels), 32-bit
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Data Transfer Rate
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Data transfer rate or just transfer rate is the average
number of bits, characters, or blocks per unit time
passing between equipment in a data transmission
system
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Bitrate (sometimes written bit rate, data rate) is the
number of bits that are conveyed or processed per unit
of time
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The bit rate is quantified using the 'bit per second'
(bit/s or bps) unit, often in conjunction with a SI prefix
such as kilo- (kbit/s or kbps), mega- (Mbit/s or Mbps),
giga- (Gbit/s or Gbps) or tera- (Tbit/s or Tbps)
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Data Transfer - Modem
 Modem
(from modulate and demodulate) is a device
that modulates an analog carrier signal to encode
digital information, and also demodulates such a
carrier signal to decode the transmitted information
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The goal is to produce a signal that can be
transmitted easily and decoded to reproduce the
original digital data
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Modems can be used over any means of
transmitting analog signals, from driven diodes to
radio
(continued on the next slide)
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ADSL Modem
 A cable
modem is a type of modem that provides
access to a data signal sent over the cable television
infrastructure. Cable modems are primarily used to
deliver broadband Internet access, taking advantage
of unused bandwidth on a cable television network
 ADSL modem or DSL modem is a device used to connect
a single computer or router to a DSL phone line, in
order to use an ADSL service
 Some ADSL modems also manage the connection
and sharing of the ADSL service with a group of
machines: in this case, the unit is termed a DSL
router or residential gateway
(continued on the next slide)
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ADSL Modem (continued)
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Asymmetric digital subscriber line transceiver or
ATU-R, as the telephone companies call it, is a
functional block inside every ADSL modem
which actually performs modulation,
demodulation and framing
Typical user interfaces are Ethernet and USB
Although an ADSL modem working as a bridge
doesn't need an IP address, it may have one
assigned for management purposes
ADSL modem is depicted on the next slide
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ADSL Modem Sample
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References
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European Computer Driven Licence, Syllabus version 4.0,
2006.
Lecture Notes. Fundamentals of Informatics (e-version).
Based on a book by L.Z.Shaucukova. Informatics (in
Russian). Moscow, 2002. – 420 p. (translated and edited by
Anatoly Sachenko).
William Stallings. Computer Organization and Architecture:
Designing for Performance (6th edition). Prentice Hall ,
2002, 750 p.
Tucker (Editor-in-Chief), R. Cupper, F.P. Deek, and R.
Noonan (Editorial advisors), Computer Science Handbook,
Second edition, CRC Press, 2004, 2752 p.
Hysa B., Piekoszewska B., Rakowiecka K., Sobota M.,
Sołtysik-Piorunkiewicz A., Zdonek D., Zdonek I., :
Laboratorium z podstaw informatyki w zarządzaniu. Część
II. Wprowadzenie do MS Windows. MS Word.
Wydawnictwo PŚ. Gliwice 2003. Skrypt nr 2324.
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References (continued)
 Kowalczyk
G.: Word 2000 PL. Ćwiczenia praktyczne.
Helion, Gliwice 2000.
 J. Glenn Brookshear. Computer science an overview,
Sixth edition, Addison Wesley, 2001, 688 p.
 Brookshear J.G.: Informatyka w ogólnym zarysie,
Wydawnictwo WNT, Warszawa 2003.
 http://www.roz6.polsl.pl/asachenko/sutaa.html