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1. Client Server System and Remote
Connectivity

2. Types of Processing – I
Processing
Centralized Distributed

3. Types of Processing – II
• Centralized – In centralized computing, database was stored in a
server which was generally a powerful mainframe. All resources such
as data storage, program execution, and data manipulation are done
at the server end provided by the mainframe
• Distributed – In distributed processing, most of the processing is
done by the client computer and the file server only stores and
serves data

4. Client/Server Model
• Client-server model
– Combination of centralized processing model and
distributed processing model
– Client contacts server for data, formats this data and
displays it to user

5. 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

6. RF Spectrum – I
• 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)

7. RF Spectrum – II
– 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)

8. Radio Transmission
• Radio station is a broadcasting service that sends sound
or audio from transmitter to an antenna and finally 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

9. Single Frequency
• Type of radio network that operates several transmitters
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-channel repeater

10. Spread Spectrum
• Signals from different sources are combined together 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 radio
frequency band may increase

11. 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

12. 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

13. Microwave – I
• 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

14. Unidirectional Antenna
• Microwave requires two types of antenna:
• Parabolic Dish Antenna
• Horn Antenna

15. 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

16. Infrared – I
• 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 radio waves
• Known as heat or heat radiation
• IR light is used by infrared systems to carry data between
devices

17. Infrared – II
IR
Unidirectional Omnidirectional Reflective
• Unidirectional – Also called point-to-point. Uses focused
laser.
• Omnidirectional – Also called broadcast. Scattered
infrared technology used.
• Reflective – Uses optical transceivers.

18. 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)

19. 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

20. Electromagnet (EM)
• Energy traveled through a material medium or through
free space in the form of electromagnetic waves
• Wave properties EM exhibits :
– Reflection
– Refraction
– Interference
– Diffraction

21. Electromagnet (EM) - II
 Types of radiation in EM spectrum:
 Radio
 Microwaves
 Infrared
 Visible Light
 Ultraviolet
 X-rays
 Gamma rays

22. Lightwave
• Connecting LANs in two buildings using lasers is the most
modern application of lightwave transmission
• Lasers follow unidirectional path
• Each building should have its own laser and its own
photo detector
• Advantages are:
– Cost effective solution
– Offers very high bandwidth
– Very easy to install
• Major disadvantage is that laser beams cannot penetrate
rain or thick fog

23. 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

24. Types of Remote Access Connectivity
• Remote access clients can dial in from remote locations and access
resources as if they are physically attached to the network.
Types of
Remote
Access
Connectivity
Dial-up VPN Dial up
Dedicated
remote remote to the
Connection
access access Internet

25. Dedicated Connection
• A company uses a dedicated connection for
the following purposes:
• Reduce the telephone bill
• Connect at higher speed

26. Remote Access Methods
Remote
Access
Methods
Using
Using
Phone-lines Using
ISDN
And X.25
Lines
Modems

27. Virtual Private Network – I
• A private communication network provided over a
public network such as Internet

28. VPN Security – I
• Uses different methods to keep connection and data
secure
• Methods for security are:
– Firewalls – A filtering mechanism which checks the
incoming and outgoing information between the
local network and the Internet
– Encryption – Translation of data into secret code. Types of
encryption are:
• Symmetric-key – same key is used to encrypt and
decrypt
• Public-key – uses a combination of private and public
key

29. VPN Security – II
– 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 Servers – When dial-up client sends request
to establish session, request is sent to the AAA
server which checks:
• who you are (authentication)
• what you are allowed to do (authorization)
• what you actually do (accounting)

30. 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

31. 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 data transmitted
is part of private network
• Most VPNs rely on tunneling

32. 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. Also called the VPN Front
End Processor (FEP) or Network Access Server (NAS) or
Point of Presence (POS) servers

33. VPN Tunneling Protocols – I
• Many network protocols
have been implemented VPN
specifically for use with Tunneling
Protocols
VPN tunnels
• These protocols are
generally incompatible
with each other
PPTP L2TP IPSec

34. VPN Tunneling Protocols – II
• Point-to-Point Tunneling Protocol (PPTP) – Enables users
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 to operate VPNs
• Internet Protocol Security (IPSec) – Exists at the network
layer in the OSI model. Multiple related protocols
combine together to form IPSec

35. Internet Connection Sharing (ICS)
• Method for connecting multiple computers in a LAN to
the Internet through a single connection and a single IP
address
• Works with connection technologies, such as DSL,
cable modem, ISDN, dial-up and satellite.

36. 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 Internet through
the network and the ICS hosts

37. Internetworking
• Creation of Wide Area Networks (WANs) by connecting
individual Local Area Networks (LANs)
• These WANs may be connected to form even larger WANs
• Minimum two networks are connected

38. 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

39. Connectionless Internetworking – II
• Internetworking is achieved using the following:
– Gateways
– Bridges
– Routers

40. Internetwork Routing
• A connection of two or more networks using routers is
called Internetwork
• A process of forwarding data packets from source to
destination is called Internetwork routing

41. Routing Process
• Two processes are involved in routing as follows:
– Host routing
– Router routing

42. Routing Concepts
Routing
Concepts
Static
Host Router Routing And
routing routing table Dynamic
Router

43. Routing Problems
Routing
Problems
Routing Black
Loops Holes

44. Routing Infrastructure
Routing
Infra
structure
Single Multi
Flat Hierarchical
path path