chapter 17 client server system and remote connectivity
TRANSCRIPT
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Client Server System and
Remote Connectivity
Chapter 17
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Chapter 17 2
Chapter ObjectivesI
Differentiate between Centralized and Distributed
Processing
Understand Radio Frequency (RF)
Explain Microwave
Explain Infrared (IR)
Differentiate between Radio
Single Frequency andSpread Spectrum
Understand Electromagnet (EM)
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Chapter 17 3
Chapter ObjectivesII
Understand Lightwave
Explain Remote Access
Explain VPN
Explain Internet Connection Sharing (ICS)
Understand Connectionless Internetworking Explain Internetworking Routing
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Chapter 17 4
RecallI
Different types of switching are: Circuit switching
Message switching
Packet switching
Telephone services carried by the Public SwitchedTelephone Network are called Plain Old Telephone
Service (POTS). Services offered by POTS are:
Signal to carry the sound of the human voice both ways at
once called as bi-directional
Ringing signals and dial-tone
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Chapter 17 5
RecallII
X.25 is a connection-oriented packet-switching protocol
which defines the way in which connections between the
user devices and network devices are established and
maintained
Different frame relay devices are:
Data Terminal Equipment (DTE)
Data Circuit-terminating Equipment (DCE)
Services provided by ATM are:
Permanent virtual circuits (PVC)
Switched virtual circuits (SVC)
Connectionless service
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Chapter 17 6
RecallIII
Polling is a communication technique which determines
when a terminal is ready to send data
Communications scheme in which each transmitter or
source in a network sends data whenever there is a
frame to send is called ALOHA
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Chapter 17 7
Types of ProcessingI
Processing
Centralized Distributed
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Types of ProcessingII
Centralized In centralized computing, databasewas stored in a server which was generally apowerful mainframe
Distributed In distributed processing, most of theprocessing is done by the client computer and thefile server only stores and serves data
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Chapter 17 9
Client/Server Model
Client-server model Combination of centralized processing model and
distributed processing model
Client contacts server for data, formats this data anddisplays it to user
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Radio Frequency (RF)
Wireless communication technology
Uses electromagnetic waves used in radio
communication to transmit and receive data
Provides real-time access to a host computer Electromagnetic waves generated by altering
current fed to an antenna
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Chapter 17 11
RF SpectrumI
Part of electromagnetic spectrum corresponding to
radio frequencies
Consists of different frequency bands:
Extremely Low Frequency (ELF) Super Low Frequency (SLF)
Ultra Low Frequency (ULF)
Very Low Frequency (VLF)
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RF SpectrumII
Low Frequency (LF)
Medium Frequency (MF)
High Frequency (HF)
Very High Frequency (VHF) Ultra High Frequency (UHF)
Super High Frequency (SHF)
Extremely High Frequency (EHF)
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Chapter 17 13
Radio Transmission
Radio station is a broadcasting service that sendssound or audio from transmitter to an antenna andfinally to receiving device
Traditionally it broadcasts through air as radio
waves Stations broadcast these services via cables, local
wire networks, satellite and Internet
Network system where programming is distributed to
multiple stations simultaneously is a radio network
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Chapter 17 14
Single Frequency
Type of radio network that operates severaltransmitters on a single frequency is Single-Frequency Network (SFN)
Each station usually runs synchronously with others
to avoid interference Two forms of modulations such as FM and AM
operate in this manner
When SFN is used in simple form, secondary
transmitter can be called a booster or on-channelrepeater
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Chapter 17 15
Spread Spectrum
Signals from different sources are combinedtogether to fit into larger bandwidth
Information encoded into discrete packages before
spreading
Receivers then filter the coded material
To reassemble the signal, the receiver has to be
compatible
Thus, number of simultaneous users within a radiofrequency band may increase
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Frequency Hopping Spread Spectrum
Modulation technique used in spread spectrum
transmission
The frequencies are repeatedly switched between
predetermined frequencies known as hops To transfer data correctly, proper synchronization of
transmitter and receiver is necessary
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Direct Sequence Spread Spectrum
Most common modulation technology
Data is divided into smaller parts called chips
Different frequencies are used to transmit these
chips Dividing the data into chips enables the receiver to
properly reassemble the data by providing
information about the cycle of frequency changes
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MicrowaveI
Electromagnetic waves with wavelengths longer
than those of infrared light, but shorter than radio
waves
Frequency ranging between 1 and 300 GHz High frequency radio waves
Used for point-to-point and omni directional
communication of various signals
Antennas required:
Parabolic dish antenna
Horn antenna
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Chapter 17 19
Uses of microwave
In broadcasting transmissions
Widely used in television news to transmit a signal
from a remote location to a television station from a
specially equipped van Lower microwave frequencies are used in the cable
TV and Internet access
Used to transmit power over long distances
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InfraredI
Derived from the Latin word infra which means
below red
Electromagnetic radiation of wavelength longer than
that of visible light but shorter than that of radiowaves
Known as heat or heat radiation
IR light is used by infrared systems to carry data
between devices
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InfraredII
UnidirectionalAlso called point-to-point. Uses
focused laser.
Omnidirectional
Also called broadcast. Scatteredinfrared technology used.
Reflective Uses optical transceivers.
IR
Unidirectional Omnidirectional Reflective
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Applications of IR
It has an excellent potential for data transmission Standards published for using IR signals for
communication between devices such as
Keyboards
Mice
PCs
Printers
Standards published by Infrared Data Association(IrDA)
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Disadvantages of IR
Does not have penetration ability
When exposed to light, IR signals goes weak. To
resolve this problem, they should have very high
output Very expensive when used over large distances
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Chapter 17 24
Electromagnet (EM)
Energy traveled through a material medium or
through free space in the form of electromagnetic
waves
EM exhibits : Reflection
Refraction
Interference
Diffraction
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Electromagnet (EM) - II
Types of radiation in EM spectrum:
Radio
Microwaves
Infrared Visible Light
Ultraviolet
X-rays
Gamma rays
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Chapter 17 26
Lightwave
Connecting LANs in two buildings using lasers is themost modern application of lightwave transmission
Lasers follow unidirectional path
Each building should have its own laser and its ownphoto detector
Advantages are:
Cost effective solution
Offers very high bandwidth
Very easy to install
Major disadvantage is that laser beams cannotpenetrate rain or thick fog
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Using Remote Access
Communication established with a distant computer
system or computer network is called as remote
access
Remote computer becomes a host on the network
To connect to the network, a computer, a modem or
some remote access software is needed
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Types of Remote Access Connectivity
Remote access clients can dial in from remote locations andaccess resources as if they are physically attached to the
network.Types of
Remote
Access
Connectivity
Dial-up
remote
access
VPN
remote
access
Dial up
to the
Internet
Dedicated
Connection
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Remote Access Methods
Remote
Access
Methods
Using
Phone-lines
And
Modems
Using
ISDNLines
Using
X.25
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Virtual Private NetworkI
A private communication network provided over apublic network such as Internet
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VPN SecurityI
Uses different methods to keep connection and data
secure
Methods for security are:
Firewalls
A filtering mechanism which checks theincoming and outgoing information between the
local network and the Internet
EncryptionTranslation of data into secret code.
Types of encryption are: Symmetric-key
Public-key
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VPN SecurityII
IPSec
Supports two encryption modes:
Transport Encrypts only the data portion(payload) of each packet
Tunnel Encrypts both header and payload. It is
more secure AAA ServersWhen dial-up client sends request
to establish session, request is sent to the AAAserver which checks:
who you are (authentication) what you are allowed to do (authorization)
what you actually do (accounting)
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Types of VPN
VPN
Remote-Access Site-to-Site
Intranet-based Extranet-based
Remote-Access VPN Is a user-to-LAN connection
which is also called Virtual Private Dial-up Network
Site-to-Site VPN
Employs Quality Of Service
(QOS) for transport reliability and uses tunneling
and encryption for data privacy
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VPN Tunneling
Also known as port forwarding
Data intended for use only within a private network
can be transmitted through public network
Public network may not be aware that datatransmitted is part of private network
Most VPNs rely on tunneling
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Types of VPN Tunneling
Voluntary tunneling Connection setup is managed
by the VPN client
Compulsory tunneling VPN connection is
managed by the carrier network provider. Alsocalled the VPN Front End Processor (FEP) or
Network Access Server (NAS) or Point of Presence
(POS) servers
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VPN Tunneling ProtocolsI
Many network protocols
have been
implemented
specifically for use with
VPN tunnels
These protocols are
generally incompatible
with each other
VPN
Tunneling
Protocols
PPTP L2TP IPSec
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VPN Tunneling ProtocolsII
Point-to-Point Tunneling Protocol (PPTP)
Enablesusers to dial to their companies network through the
Internet
Layer Two Tunneling Protocol (L2TP) Exists at
data link layer in the OSI model and allows ISPs tooperate VPNs
Internet Protocol Security (IPSec) Exists at the
network layer in the OSI model. Multiple related
protocols combine together to form IPSec
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Internet Connection Sharing (ICS)
Method for connecting multiple computers in aLAN to the Internet through a single connectionand a single IP address
Works with connection technologies, such as DSL,
cable modem, ISDN, dial-up and satellite.
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Internet Connection Sharing - II
Comprises of the following: ICS Host Device which has a modem or broadband
interface that establishes connection to the Internet
ICS clients Devices that connect to the Internetthrough the network and the ICS hosts
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Case Study
The network administrator John of the Mumbai
branch of MoneyMaker bank has configured ICS in
the branch. Whenever the client computersconnected to the ICS host use an Internet program
an error message appears which says the mail
server cannot be located
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Problem
The client side browser is set to use a proxy server
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Suggested Solution
The administrator should verify that the client
computer is not configured to use a proxy server
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Internetworking
Creation of Wide Area Networks (WANs) byconnecting individual Local Area Networks (LANs)
These WANs may be connected to form even larger
WANs
Minimum two networks are connected
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Connectionless Internetworking and
Protocol
In connectionless Internetworking, data can be
sent without any need to establish a connection
first
Thus, there is no guarantee of delivery of data An ISO network layer datagram protocol
Similar to the Internet Protocol (IP)
Also named as ISO-IP
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Connectionless InternetworkingII
Internetworking is achieved using the following:
Gateways
Bridges
Routers
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Internetwork Routing
A connection of two or more networks using routersis called Internetwork
A process of forwarding data packets from source to
destination is called Internetwork routing
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Routing Process
Two processes are involved in routing as follows:
Host routing
Router routing
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Routing Concepts
Routing
Concepts
Host
routing
Router
routing
Routing
table
Static
And
Dynamic
Router
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Routing Problems
Routing
Problems
Routing
Loops
Black
Holes
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Routing Infrastructure
Routing
Infra
structure
Single
path
Multi
path Flat Hierarchical
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SummaryI
A network connected to the Internet but isolated from theInternet is called as a private network
Centralized processing is performed in one computer orin a cluster of computers in a single location
When more than one computer or processor is used toexecute an application it is called as a distributedprocessing
The combination of centralized processing model anddistributed processing model is called the client-servermodel
S II
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SummaryII
Radio Frequency (RF) is the wireless communicationtechnology which uses electromagnetic waves used in
radio communication to transmit and receive data
The part of the electromagnetic spectrum corresponding
to radio frequencies is called as the radio frequencyspectrum
Electromagnetic waves with wavelengths longer than
those of infrared light, but shorter than those radio waves
are called microwaves
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SummaryIII
A type of radio network that operates severaltransmitters on a single frequency is called as a Single-Frequency Network (SFN)
When the information been sent is transmitted over a
frequency band which is much wider than the minimumbandwidth needed to send that information then it iscalled as a spread spectrum
Communication established with a distant computersystem or computer network is called as remote access
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SummaryIV
A method for connecting multiple computers in a LAN tothe Internet through a single connection and a single IPaddress is called as Internet Connection Sharing (ICS)
The creation of Wide Area Networks (WANs) by
connecting individual Local Area Networks (LANs) iscalled as Internetworking
A computer networking device that forwards datapackets towards its destination is called as a router
The process of transferring data across an Internetwork
from a source host to a destination host is called asrouting