Client server system and remote connectivity


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Client server system and remote connectivity

  1. 1. Client Server System and Remote Connectivity
  2. 2. Types of Processing – I ProcessingCentralized Distributed
  3. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 14. Unidirectional Antenna• Microwave requires two types of antenna:• Parabolic Dish Antenna• Horn Antenna
  15. 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. 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. 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. 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. 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. 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. 21. Electromagnet (EM) - II Types of radiation in EM spectrum:  Radio  Microwaves  Infrared  Visible Light  Ultraviolet  X-rays  Gamma rays
  22. 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. 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. 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. 25. Dedicated Connection• A company uses a dedicated connection for the following purposes:• Reduce the telephone bill• Connect at higher speed
  26. 26. Remote Access Methods Remote Access Methods Using UsingPhone-lines Using ISDN And X.25 Lines Modems
  27. 27. Virtual Private Network – I• A private communication network provided over a public network such as Internet
  28. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 39. Connectionless Internetworking – II• Internetworking is achieved using the following: – Gateways – Bridges – Routers
  40. 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. 41. Routing Process• Two processes are involved in routing as follows: – Host routing – Router routing
  42. 42. Routing Concepts Routing Concepts Static Host Router Routing Androuting routing table Dynamic Router
  43. 43. Routing Problems Routing ProblemsRouting Black Loops Holes
  44. 44. Routing Infrastructure Routing Infra structureSingle Multi Flat Hierarchical path path