Networks (40 slides)

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Lecture 4: Information
Networks (40 slides)

Lecturer:

Prof. Anatoly Sachenko

Information technology

2

Lecture Overview



LAN and WAN


Topologies and Architectures of Computer
Networks


Intranet and Extranet


The Internet


The Telephone Network in Computing


Data Transfer


Modem

3

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


4


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)



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

WAN

5

LAN and WAN
Illustration
s

6


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
)


LAN and WAN


Client/Server

7


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


LAN and WAN
-

Client/Server
(continued)

8

LAN and WAN


Group Working



LAN and WAN have applications, which use client
-
server 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


9

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


Ring



Treelike


Star



Cellular

10

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 Ring

is a
ring

network


Its 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


It’s implemented and used by IBM


11


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



Architectures of Computer Networks
-

FDDI

12




Wireless networks

are used wherein the gasket of
cables is laboured, inadvisable or simply impossible


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
two adapters of networks are set in which


wireless and cable



Architectures of Computer Networks


Wireless Networks

13


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


Architectures of Computer Networks


Wireless Networks
(continued)

14

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)

15

Intranet
-

Illustration

16


An
extranet

is a private network


An
extranet

can be viewed as part of a company's
Intranet that is extended to users outside the
company


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



Extranet


17

Extranet (continued)

18

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)

19


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


T
here 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)



The Internet
Protocols

20

The Internet
Protocols
(continued)


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
)




21


T
he Internet

has many
c
ommon 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)





The Internet
Uses

22


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
-
to
-
peer 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)


The Internet
Uses

(continued)

23


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


The Internet
Uses

(continued)

24


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
)


The Internet
-

World Wide Web

25


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


World Wide Web

(continued)

26

World Wide Web
Illustration


27

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 packet
-
switched 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

28


Integrated Services Digital Network

(
ISDN
)

is a circuit
-
switched 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)


The Telephone Network in Computing
-

ISDN

29


In a videoconference,
ISDN

provides simultaneous
voice, video, and text transmission between
individual desktop videoconferencing systems and
group (room) videoconferencing systems


The purpose of the
ISDN

is to provide fully
integrated digital services to the user


These services fall under three categories:



bearer services, supplementary services and
teleservices



The Telephone Network in Computing
-

ISDN

(continued
)

30

The Telephone Network in Computing


ISDN Illustration

31


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


It’s typically less than 5 km




The Telephone Network in Computing
-

ADSL

32


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


A
discrete signal

or
discrete
-
time signal

is a time series,
perhaps a signal that has been sampled from a
continuous
-
time signal


Unlike a continuous
-
time signal, a
discrete
-
time signal

is not a function of a continuous
-
time argument


It’s is a sequence of quantities

and
each value in
the sequence is called a sample





Data Transfer
-

Analog and Discrete Signals

33


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



8
-
bit (256 levels), 16
-
bit (65,536 levels), 32
-
bit
(4,3 billion levels), and so on

Data Transfer


Digital Signals

34


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


Bitrate

(sometimes written
bit rate
,
data rate
) is the
number of bits that are conveyed or processed per unit
of time


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)

Data Transfer

Rate

35


Modem

(from
mo
dulate and
dem
odulate) 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


The goal is to produce a signal that can be
transmitted easily and decoded to reproduce the
original digital data


Modems can be used over any means of
transmitting analog signals, from driven diodes to
radio

(continued on the next slide)

Data Transfer
-

Modem

36


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)



ADSL Modem

37


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


ADSL Modem

(continued)

38

ADSL Modem Sample

39

References


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.

40

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
.


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:
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