Chapter 17 Client Server System and Remote Connectivity

8/10/2019 Chapter 17 Client Server System and Remote Connectivity

1/54

Client Server System and

Remote Connectivity

Chapter 17


2/54

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)


3/54

Chapter 17 3

Chapter ObjectivesII

Understand Lightwave

Explain Remote Access

Explain VPN

Explain Internet Connection Sharing (ICS)

Understand Connectionless Internetworking Explain Internetworking Routing


4/54

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


5/54

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


6/54

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


7/54

Chapter 17 7

Types of ProcessingI

Processing

Centralized Distributed


8/54

Chapter 17 8

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


9/54

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


10/54

Chapter 17 10

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


11/54

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)


12/54

Chapter 17 12

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)


13/54

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


14/54

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


15/54

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


16/54

Chapter 17 16

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


17/54

Chapter 17 17

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


18/54

Chapter 17 18

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


19/54

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


20/54

Chapter 17 20

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


21/54

Chapter 17 21

InfraredII

UnidirectionalAlso called point-to-point. Uses

focused laser.

Omnidirectional

Also called broadcast. Scatteredinfrared technology used.

Reflective Uses optical transceivers.

IR

Unidirectional Omnidirectional Reflective


22/54

Chapter 17 22

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)


23/54

Chapter 17 23

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


24/54

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


25/54

Chapter 17 25

Electromagnet (EM) - II

Types of radiation in EM spectrum:

Radio

Microwaves

Infrared Visible Light

Ultraviolet

X-rays

Gamma rays


26/54

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


27/54

Chapter 17 27

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


28/54

Chapter 17 28

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


29/54

Chapter 17 29

Remote Access Methods

Remote

Access

Methods

Using

Phone-lines

And

Modems

Using

ISDNLines

Using

X.25


30/54

Chapter 17 30

Virtual Private NetworkI

A private communication network provided over apublic network such as Internet


31/54

Chapter 17 31

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


32/54

Chapter 17 32

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)


33/54

Chapter 17 33

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


34/54

Chapter 17 34

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


35/54

Chapter 17 35

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


36/54

Chapter 17 36

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


37/54

Chapter 17 37

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


38/54

Chapter 17 38

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.


39/54

Chapter 17 39

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


40/54

Chapter 17 40

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


41/54

Chapter 17 41

Problem

The client side browser is set to use a proxy server


42/54

Chapter 17 42

Suggested Solution

The administrator should verify that the client

computer is not configured to use a proxy server


43/54

Chapter 17 43

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


44/54

Chapter 17 44

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


45/54

Chapter 17 45

Connectionless InternetworkingII

Internetworking is achieved using the following:

Gateways

Bridges

Routers


46/54

Chapter 17 46

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


47/54

Chapter 17 47

Routing Process

Two processes are involved in routing as follows:

Host routing

Router routing


48/54

Chapter 17 48

Routing Concepts

Routing

Concepts

Host

routing

Router

routing

Routing

table

Static

And

Dynamic

Router


49/54

Chapter 17 49

Routing Problems

Routing

Problems

Routing

Loops

Black

Holes


50/54

Chapter 17 50

Routing Infrastructure

Routing

Infra

structure

Single

path

Multi

path Flat Hierarchical


51/54

Chapter 17 51

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


52/54

Chapter 17 52

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


53/54

Chapter 17 53

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


54/54

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

Documents

Chapter 17 Client Server System and Remote Connectivity