MLM-III

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING8. List the advantages of process migration?  Reducing average response time of processes  Speeding up individual jobs  Utilizing resources effectively  Reducing network traffic  Improving system reliability9. What are the motivations used in threads?  The overheads involved in creating a new process are in general considerably greater than those of creating a new thread within process.  Switching between threads sharing the same address space is considerably cheaper than switching between processes that have their own address spaces.  Threads allow parallelism to be combined with sequential execution and blocking system calls.  Parallelism improves performance and blocking system calls make programming easier.10. What are the ways to organize the threads?  Dispatcher-workers model  Team model  Pipeline model11. What are the issues in designing a threads package?  Threads creation  Threads termination  Threads synchronization  Threads scheduling  Signal handling12. What are the techniques used for scheduling process in distributed system?  Task assignment approach  Load-balancing approach  Load-Sharing approach13. List the various features of global scheduling algorithm?  No A priori knowledge about the processes  Dynamic in nature  Quick decision-making capability  Balanced system performance and scheduling overhead  Stability  Scalability  Fault tolerance 51

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING14. Define Task Assignment approach? Task assignment approach is a process is considered to be composed of multipletasks and the goal is to find an optimal assignment policy for the tasks of an individualprocess.15. Explain about load-balancing approach? Load-balancing algorithm tries to balance the total system load by transparentlytransferring the workload from heavily loaded nodes to lightly loaded nodes in anattempt to ensure good overall performance relative to some specific metric of systemperformance. Thus the basic goal of almost all the load balancing algorithms is tomaximize the total system throughput.16. Discuss about the taxonomy of load-balancing algorithms?  Static versus Dynamic  Deterministic versus Probabilistic  Centralized versus Distributed  Cooperative versus Non cooperative17. What are the difficult tasks involved in load-balancing algorithms?  Load estimation policy  Process transfer policy  State information exchange policy  Priority assignment policy  Migration limiting policy18. What is a thread? A thread is a program line under execution. Thread sometimes called a light-weight process, is a basic unit of CPU utilization; it comprises a thread id, a programcounter, a register set, and a stack19. What are the issues in load-sharing algorithms?  Load estimation policy  Process transfer policy  Location policy  State information exchange policy20. Define load-sharing approach? Load sharing approach, which simply attempts to conserve the ability of thesystem to perform work by assuming that no node is idle while processes wait for beingprocessed PART-B1. Briefly explain about process migration? Discuss the feature, mechanism andadvantage of process migration?  Process migration  Features 52

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Transparency  Minimal interference  Minimal residual dependencies  Efficiency  Robustness  Mechanisms  Address space transfer mechanism  Message forwarding mechanisms  Origin site mechanism  Link traversal mechanism  Process migration in heterogeneous systems  Advantages of process migration2. Explain detail about resource management?  Introduction  Task assignment approach  Load balancing approach  Load sharing approach  Features of scheduling algorithms  No a priori knowledge about the processes  Dynamic in nature  Quick decision-making capability  Balanced system performance and scheduling overhead  Stability  Scalability  Fault tolerance  Fairness of service  Task Assignment approach  The basic idea  Finding an optimal assignment  Load balancing approach  A taxonomy of load-balancing algorithms  Static versus Dynamic  Deterministic versus probabilistic  Centralized versus distributed  Cooperative versus Noncooperative  Issues in designing load-balancing algorithms  Load estimation Policies  Process Transfer policies  Location Policies 53

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  State information Exchange policies  Priority Assignment policies  Migration Limiting policies  Loan sharing Approach  Issues in designing load-sharing algorithms  Load estimation Policies  Process Transfer policies  Location Policies  State information Exchange policies3. Explain about Task Assignment approach?  The basic idea  Finding an optimal Assignment4. Explain about load balancing approach? Discuss the issues in load-balancingalgorithm?  Load balancing approach  A taxonomy of load-balancing algorithms  Static versus Dynamic  Deterministic versus probabilistic  Centralized versus distributed  Cooperative versus Noncooperative  Issues in designing load-balancing algorithms  Load estimation Policies  Process Transfer policies  Location Policies  State information Exchange policies  Priority Assignment policies  Migration Limiting policies5. Explain about load sharing approach? Discuss the issues in load-sharingalgorithm?  Loan sharing Approach  Issues in designing load-sharing algorithms  Load estimation Policies  Process Transfer policies  Location Policies  State information Exchange policies6. Discuss the issues related to thread programming, thread lifetime, threadsynchronization, scheduling and implementation? (May/jun2012)  Motivations for threads  Models for organizing threads  Dispatcher-workers model 54

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Team model  Pipeline model  Issues in designing a threads package  Threads creation  Threads termination  Threads synchronization  Threads scheduling  Implementation  Thread management  Threads synchronization  Threads scheduling  Signal handling  Error handling 55

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING Anna University B.E./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2012 Eighth Semester Computer Science and Engineering CS 2056/CS 804- DISTRIBUTED SYSTEMS (common to Information Technology) (Regulation 2008)Time: Three hoursMaximum: 100 marksAnswer ALL questions. PART A-(10*2=20 marks)1. What is the main objective of distributed systems?2. Define marshaling.3. Differentiate static and dynamic invocation methods.4. Define client stub and server stub.5. What do you mean by name resolution?6. What is the use closure mechanism?7. What do you mean by clock skew and clock drift?8. What are the disadvantage of multicast?9. Differentiate lazy release and eager release consistency.10. Write the definition for sequential consistency. PART B-(5*16=80 marks)11. (a) (i) State and explain the challenges of distributed systems. (ii) Define the term distributed system. Explain with two examples. (10+6) Or (b) (i) Briefly explain group communication. (ii) Explain how inter process communication is handled in UNIX.(10+6)12. (a) Discuss the design and implementation issues in Remote Method Invocation.(16) Or(b) Describe the architecture for multi threaded servers. Discuss the issues related tothread progamming, thread lifetime, thread synchronization, scheduling andimplementation. (16)13.(a) What is name service? What are its goals? How it is implemented? What isdirectory service? (16) Or(b) (i) Name all modules of file system operations and write in detail aboutdistributed file system requirements.(ii) Discuss the mounting issues of remote file systems on NFS client (8+8) 56

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING14.(a) (i) What is the goal of an election algorithm? Explain it detail. (8)(ii) Explain how mutual exclusion is handled in distributed system. (8) Or(b) (i) Describe the internal and external synchronization of Physical clocks.(8)(ii) Explain the Chandy and Lamports snapshot algorithm for determining the globalstates of distributed systems. (8)15.(a) Contribute your comments on granularity and page replacement issues in the designof distributed shared memory systems. (16) Or(b) Explain the different consistency models for distributed. (16) 57

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING IT6601 - MOBILE COMPUTINGIT6601 MOBILE COMPUTING LTPC3003UNIT I INTRODUCTION 9Mobile Computing – Mobile Computing Vs wireless Networking – MobileComputing Applications – Characteristics of Mobile computing – Structure of MobileComputing Application. MAC Protocols – Wireless MAC Issues – Fixed AssignmentSchemes – Random Assignment Schemes – Reservation Based Schemes.UNIT II MOBILE INTERNET PROTOCOL AND TRANSPORT LAYER 9Overview of Mobile IP – Features of Mobile IP – Key Mechanism in Mobile IP –Route Optimization. Overview of TCP/IP – Architecture of TCP/IP- Adaptation ofTCP Window – Improvement in TCP Performance.UNIT III MOBILE TELECOMMUNICATION SYSTEM 9Global System for Mobile Communication (GSM) – General Packet Radio Service(GPRS) – Universal Mobile Telecommunication System (UMTS).UNIT IV MOBILE AD-HOC NETWORKS 9Ad-Hoc Basic Concepts – Characteristics – Applications – Design Issues – Routing –Essential of Traditional Routing Protocols –Popular Routing Protocols – VehicularAd Hoc networks ( VANET) – MANET Vs VANET – Security.UNIT V MOBILE PLATFORMS AND APPLICATIONS 9Mobile Device Operating Systems – Special Constrains & Requirements –Commercial Mobile Operating Systems – Software Development Kit: iOS, Android,BlackBerry, Windows Phone – M-Commerce – Structure – Pros & Cons – MobilePayment System – Security Issues.TOTAL: 45 PERIODSTEXT BOOK:1. Prasant Kumar Pattnaik, Rajib Mall, “Fundamentals of Mobile Computing”, PHI Learning Pvt. Ltd, New Delhi – 2012.REFERENCES:1. Jochen H. Schiller, “Mobile Communications”, Second Edition, Pearson Education,New Delhi, 2007.2. Dharma Prakash Agarval, Qing and An Zeng, \"Introduction to Wireless and Mobilesystems\", Thomson Asia Pvt Ltd, 2005.3. Uwe Hansmann, Lothar Merk, Martin S. Nicklons and Thomas Stober, “Principlesof Mobile Computing”, Springer, 2003.4. William.C.Y.Lee,“Mobile Cellular Telecommunications-Analog and DigitalSystems”, Second Edition,Tata Mc Graw Hill Edition ,2006.5. Android Developers : http://developer.android.com/index.html6. Apple Developer : https://developer.apple.com/7. Windows Phone Dev Center : http://developer.windowsphone.com8. BlackBerry Developer : http://developer.blackberry.com/ 58

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING IT6601 - MOBILE COMPUTING Index SheetUNIT TOPIC PAGE NUMBER No. Notes PART-A PART-B I Introduction 60 60 63II Mobile Internet Protocol And 70 71 74 77 77 79 Transport Layer 81 82 85III Mobile Telecommunication System 88 89 92IV Mobile Ad-Hoc NetworksV Mobile Platforms And ApplicationsANNA UNIVERSITY QUESTION PAPER 100 59

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING UNIT - I INTRODUCTIONMobile Computing – Mobile Computing Vs wireless Networking – MobileComputing Applications – Characteristics of Mobile computing – Structure of MobileComputing Application. MAC Protocols – Wireless MAC Issues – Fixed AssignmentSchemes – Random Assignment Schemes – Reservation Based Schemes. KEY NOTES  Mobile Computing  Mobile Computing Vs Wireless Networking  Wireless network based on fixed infrastructures  Wireless network having no fixed infrastructures  Mobile Computing Applications  Characteristics of Mobile computing  Ubiquity  Location awareness  Adaptation  Broadcast  Personalization  Structure of Mobile Computing Application  Presentation tier  Application tier  Data tier  MAC Protocols  Properties required of MAC protocols  Wireless MAC Issues  The hidden and exposed terminal problems in an infrastructure-less network  Fixed Assignment Schemes  Frequency division multiple access (FDMA)  Time division multiple access (TDMA)  Code division multiple access (CDMA)  Random Assignment Schemes  ALOHA Scheme  CSMA Scheme  Reservation Based Schemes  MACA PART-A 1. What is meant by mobile computing? Mobile computing is widely described as the ability to compute remotely while onthe move. This is a new and fast emerging discipline that has made it possible forpeople to access information from anywhere and at anytime. 60

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING Computing denotes the capability to automatically carry out certain processingrelated to service invocations on a remote computer. Mobility, on the other hand, provides the capability to change location whilecommunicating to invoke computing services at some remote computers. 2. Give the advantages of mobile computing. Mobile computing is the tremendous flexibility it provides to the users. The userneed not be tethered to the chair in front of his desktop, but can move locally or evento faraway places and at the same time achieve what used to be performed whilesitting in front of a desktop. 3. Differentiate wireless networking vs. mobile computing Wireless networking provides the basic communication infrastructure necessary tomake this possible. Mobile computing essentially denotes accessing information and remotecomputational services while on the move. Mobile computing is based on wirelessnetworking and helps one to invoke computing services on remote servers while onthe move: be it be office, home, conference, hotel, and so on. 4. Define the functions of three tiers in mobile computing environment.Presentation tier:- The topmost level of mobile computing application concerns theuser interface. A good user interface facilitates the users to issue requests and topresent the results to the them meaningfully.Application tier:- This layer has the vital responsibility of making logical decisionsand performing calculations. It also moves and processes data between thepresentation and data layers.Data tier:- The data tier is responsible for providing the basic facilities of data storage,access, and manipulation. 5. Give the responsibility of MAC protocol. (Nov/Dec 2011) The MAC protocol is a sublayer of the data link layer protocol and it directlyinvokes the physical layer protocol. The primary responsibility of a MAC protocol isto enforce discipline in the access of a shared channel when multiple nodes contend toaccess that channel. 6. Give the difficulties if MAC protocol used in wireless medium. A MAC protocol in a wireless medium is much more complex than its wired counterpart. (i) A collision detection scheme is difficult to implement in a wireless environment, since collisions are hard to be detected by the transmitting nodes. (ii) In infrastructure-less networks, the issue of hidden and exposed terminals make a MAC protocol extremely inefficient unless special care is taken to overcome these problems. 7. State the categories of MAC protocols. (Apr/May 2009) A large number of MAC protocols have been proposed. These MAC protocols canbe broadly divided into the following three categories. 61

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING (i) Fixed assignment schemes - It is usually called circuit-switched schemes. In this schemes, the resources required for a call are assigned for the entire duration of the call. (ii) Random assignment schemes – It is a packet switched schemes. The random assignment schemes are comparable to the connection-less packet- switching schemes. (iii)Reservation-based schemes - It is a packet switched schemes. A node makes explicit reservation of the channel for an entire call before transmitting. 8. Give the different categories of fixed assignment schemes.  Frequency Division Multiple Access (FDMA)  Time Division Multiple Access (TDMA)  Code Division Multiple Access (CDMA) 9. Define FDMA. The available bandwidth (frequency range) is divided into many narrowerfrequency bands called channels. Each user is allocated a forward link (channel) forcommunicating from it (mobile handset) to the base station (BS), and a reversechannel for communicating from the BS to it. 10. Define TDMA. TDMA is an access method in which multiple nodes are allotted different timeslots to access the same physical channel. That is, the timeline is divided into fixed-sized time slots and these are divided among multiple nodes who can transmit. Eachuser of the channel owns the channel for exclusive use for one time slot at a time in around robin fashion. 11. Define CDMA. Multiple users are allotted different codes that consist of sequences of 0 and 1 to access the same channel. 12. How to distinguish transmission from different nodes? Two vectors are said to be orthogonal if their inner product=0. Let p and q be two vectors and suppose p=(2,5,0) and q=(0,0,17), then the inner product of p*q=(2*0+5*0+0*17)=0. For good autocorrelation, binary 0 is represented as -1 and binary 1 is represented as +1. Let the binary sequence be 1001, then the representation sequence is +1-1-1+1. 13. What are different types of random assignment schemes? There are a number of random assignment schemes that are used in MAC protocols. A few important ones are the following:  ALOHA  Slotted ALOHA  CSMA  CSMA/CD  CSMA/CA 62

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING 14. Describe ALOHA scheme. It is a simple communication scheme. If a node has data to send, it begins totransmit. The first step implies that pure ALOHA does not check whether the channelis busy before transmitting. If the frame successfully reaches the destination(receiver), the next frame is sent. If the frame fails to be received at the destination, itis sent again. 15. Define CSMA scheme. A popular MAC arbitration technique is the Carrier Sense Multiple Access(CSMA). In this technique, a node senses the medium before starting to transmit. If itsenses that some transmission is already underway, it defers its transmission. Twopopular extensions of the basic CSMA technique are the Collision Detection(CSMA/CD) and the Collision Avoidance (CSMA/CA) techniques. 16. Describe reservation based scheme. A basic form of the reservation scheme is the RTS/CTS scheme. In an RTS/CTSscheme, a sender transmits an RTS (Ready To Send) packet to the receiver before theactual data transmission. On receiving this, the receiver sends a CTS (Clear to Send)packet, and the actual data transfer commences only after that. When the other nodessharing the medium sense the CS packet, they refrain from transmitting until thetransmission from the sending node is complete. 17. Define MACA. MACA stands for Multiple Access Collision Avoidance. MACA solves thehidden/exposed terminal problems by regulating the transmitter power. A noderunning MACA requests to use the medium by sending an RTS to the receiver. Sinceradio signals propagate omni-directionally, every terminal within the sender’s radiorange will hear this and then refrain from transmitting. As soon as the receiver isready to receive data, it responds with a CTS. PART-B 1. Explain detail about Mobile computing? The rapidly expanding technology of cellular communication, wireless LANs,and satellite services will make information accessible anywhere and at any time.Regardless of size, most mobile computers will be equipped with a wirelessconnection to the fixed part of the network, and, perhaps, to other mobile computers.The resulting computing environment, which is often referred to as mobile ornomadic computing, no longer requires users to maintain a fixed and universallyknown position in the network and enables almost unrestricted mobility. Mobilityand portability will create an entire new class of applications and, possibly, newmassive markets combining personal computing and consumer electronics. Mobile Computing is an umbrella term used to describe technologies thatenable people to access network services anyplace, anytime, and anywhere. A communication device can exhibit any one of the following characteristics:  Fixed and wired: This configuration describes the typical desktop computer in an office. Neither weight nor power consumption of the devices allow for 63

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING mobile usage. The devices use fixed networks for performance reasons.  Mobile and wired: Many of today’s laptops fall into this category; users carry the laptop from one hotel to the next, reconnecting to the company’s network via the telephone network and a modem.  Fixed and wireless: This mode is used for installing networks, e.g., in historical buildings to avoid damage by installing wires, or at trade shows to ensure fast network setup.  Mobile and wireless: This is the most interesting case. No cable restricts the user, who can roam between different wireless networks. Most technologies discussed in this book deal with this type of device and the networks supporting them. Today’s most successful example for this category is GSM with more than 800 million users. 2. Explain about applications of Mobile Computing? (Apr/May 2011) In many fields of work, the ability to keep on the move is vital in order to utilizetime efficiently. The importance of Mobile Computers has been highlighted in manyfields of which a few are described below:  Vehicles: Music, news, road conditions, weather reports, and other broadcast information are received via digital audio broadcasting (DAB) with 1.5 Mbit/s. For personal communication, a universal mobile telecommunications system (UMTS) phone might be available offering voice and data connectivity with 384 kbit/s. The current position of the car is determined via the global positioning system (GPS). Cars driving in the same area build a local ad-hoc network for the fast exchange of information in emergency situations or to help each other keep a safe distance. In case of an accident, not only will the airbag be triggered, but the police and ambulance service will be informed via an emergency call to a service provider. Buses, trucks and trains are already transmitting maintenance and logistic information to their home base, which helps to improve organization (fleet management), and saves time and money.  Emergencies: An ambulance with a high-quality wireless connection to a hospital can carry vital information about injured persons to the hospital from the scene of the accident. All the necessary steps for this particular type of accident can be prepared and specialists can be consulted for an early diagnosis. Wireless networks are the only means of communication in the case of natural disasters such as hurricanes or earthquakes. In the worst cases, only decentralized, wireless ad-hoc networks survive.  Business: Managers can use mobile computers say, critical presentations to major customers. They can access the latest market share information. At a small recess, they can revise the presentation to take advantage of this information. They can communicate with the office about possible new offers and call meetings for discussing responds to the new proposals. Therefore, mobile computers can leverage competitive advantages. A travelling salesman today needs instant access to the company’s database: to ensure that files on 64

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING his or her laptop reflect the current situation, to enable the company to keep track of all activities of their travelling employees, to keep databases consistent etc. With wireless access, the laptop can be turned into a true mobile office, but efficient and powerful synchronization mechanisms are needed to ensure data consistency.  Credit Card Verification: At Point of Sale (POS) terminals in shops and Supermarkets, when customers use credit cards for transactions, the intercommunication required between the bank central computer and the POS terminal, in order to effect verification of the card usage, can take place quickly and securely over cellular channels using a mobile computer unit. This can speed up the transaction process and relieve congestion at the POS terminals.  Replacement of Wired Networks: wireless networks can also be used to replace wired networks, e.g., remote sensors, for tradeshows, or in historic buildings. Due to economic reasons, it is often impossible to wire remote sensors for weather forecasts, earthquake detection, or to provide environmental information. Wireless connections, e.g., via satellite, can help in this situation.  Infotainment: wireless networks can provide up-to-date information at any appropriate location. The travel guide might tell you something about the history of a building (knowing via GPS, contact to a local base station, or triangulation where you are) downloading information about a concert in the building at the same evening via a local wireless network. Another growing field of wireless network applications lies in entertainment and games to enable, e.g., ad-hoc gaming networks as soon as people meet to play together. 3. State the categories of MAC protocols. (Nov/Dec 2012) A large number of MAC protocols have been proposed. These MAC protocolscan be broadly divided into the following three categories. (iv)Fixed assignment schemes - It is usually called circuit-switched schemes. In this schemes, the resources required for a call are assigned for the entire duration of the call. (v) Random assignment schemes – It is a packet switched schemes. The random assignment schemes are comparable to the connection-less packet- switching schemes. (vi)Reservation-based schemes - It is a packet switched schemes. A node makes explicit reservation of the channel for an entire call before transmitting. (vii) The Media Access Control (MAC) data communication protocol sub- layer, also known as the Medium Access Control, is a sublayer of the Data Link Layer specified in the seven-layer OSI model (layer 2). The hardware that implements the MAC is referred to as a Medium Access Controller. The MAC sub-layer acts as an interface between the Logical Link Control (LLC) sublayer and the network's physical layer. The MAC layer emulates 65

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGa full-duplex logical communication channel in a multi-point network.This channel may provide unicast, multicast or broadcast communicationservice.  Motivation for a specialized MAC One of the most commonly used MAC schemes for wired networks is carriersense multiple access with collision detection (CSMA/CD). In this scheme, a sendersenses the medium (a wire or coaxial cable) to see if it is free. If the medium is busy,the sender waits until it is free. If the medium is free, the sender starts transmittingdata and continues to listen into the medium. If the sender detects a collision whilesending, it stops at once and sends a jamming signal. But this scheme doest work wellwith wireless networks. The problems are: a) Signal strength decreases proportional to the square of the distance b) The sender would apply CS and CD, but the collisions happen at the receiver c) It might be a case that a sender cannot “hear” the collision, i.e., CD does not work d) Furthermore, CS might not work, if for e.g., a terminal is “hidden” 4. Explain different categories of fixed assignment schemes.  Frequency Division Multiple Access (FDMA)  Time Division Multiple Access (TDMA)  Code Division Multiple Access (CDMA) Frequency division multiplexing (FDM) describes schemes to subdivide thefrequency dimension into several non-overlapping frequency bands. 66

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING Frequency Division Multiple Access is a method employed to permit severalusers to transmit simultaneously on one satellite transponder by assigning a specificfrequency within the channel to each user. Each conversation gets its own, unique,radio channel. The channels are relatively narrow, usually 30 KHz or less and aredefined as either transmit or receive channels. A full duplex conversation requires atransmit & receive channel pair. FDM is often used for simultaneous access to themedium by base station and mobile station in cellular networks establishing a duplexchannel. A scheme called frequency division duplexing (FDD) in which the twodirections, mobile station to base station and vice versa are now separated usingdifferent frequencies.  FDM For Multiple Access and Duplex The two frequencies are also known as uplink, i.e., from mobile station to basestation or from ground control to satellite, and as downlink, i.e., from base station tomobile station or from satellite to ground control. The basic frequency allocationscheme for GSM is fixed and regulated by national authorities. All uplinks use theband between 890.2 and 915 MHz, all downlinks use 935.2 to 960 MHz. According toFDMA, the base station, shown on the right side, allocates a certain frequency for up-and downlink to establish a duplex channel with a mobile phone. Up and downlinkhave a fixed relation. If the uplink frequency is fu = 890 MHz + n·0.2 MHz, thedownlink frequency is fd = fu + 45 MHz,i.e., fd = 935 MHz + n·0.2 MHz for a certain channel n. The base station selects thechannel. Each channel (uplink and downlink) has a bandwidth of200 kHz. Thisscheme also has disadvantages. While radio stations broadcast 24 hours a day, mobilecommunication typically takes place for only a few minutes at a time. Assigning aseparate frequency for each possible communication scenario would be a tremendouswaste of (scarce) frequency resources. Additionally, the fixed assignment of a 67

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGfrequency to a sender makes the scheme very inflexible and limits the number ofsenders.  TDMA A more flexible multiplexing scheme for typical mobile communications istime division multiplexing (TDM). Compared to FDMA, time division multipleaccess (TDMA) offers a much more flexible scheme, which comprises alltechnologies that allocate certain time slots for communication. Now synchronizationbetween sender and receiver has to be achieved in the time domain. Again this can bedone by using a fixed pattern similar to FDMA techniques, i.e., allocating a certaintime slot for a channel, or by using a dynamic allocation scheme. Listening to different frequencies at the same time is quite difficult, butlistening to many channels separated in time at the same frequency is simple. Fixedschemes do not need identification, but are not as flexible considering varyingbandwidth requirements.  Fixed TDM The simplest algorithm for using TDM is allocating time slots for channels ina fixed pattern. This results in a fixed bandwidth and is the typical solution forwireless phone systems. MAC is quite simple, as the only crucial factor is accessingthe reserved time slot at the right moment. If this synchronization is assured, eachmobile station knows its turn and no interference will happen. The fixed pattern canbe assigned by the base station, where competition between different mobile stationsthat want to access the medium is solved. 5. Explain different types of random assignment schemes? There are a number of random assignment schemes that are used in MACprotocols. A few important ones are the following:  ALOHA  Slotted ALOHA  CSMA  CSMA/CD  CSMA/CA 68

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Classical Aloha In this scheme, TDM is applied without controlling medium access. Here eachstation can access the medium at any time as shown below: This is a random access scheme, without a central arbiter controlling accessand without coordination among the stations. If two or more stations access themedium at the same time, a collision occurs and the transmitted data is destroyed.Resolving this problem is left to higher layers (e.g., retransmission of data). Thesimple Aloha works fine for a light load and does not require any complicated accessmechanisms.  Slotted Aloha The first refinement of the classical Aloha scheme is provided by theintroduction of time slots (slotted Aloha). In this case, all senders have to besynchronized; transmission can only start at the beginning of a time slot as shownbelow. The introduction of slots raises the throughput from 18 per cent to 36 per cent,i.e., slotting doubles the throughput. Both basic Aloha principles occur in manysystems that implement distributed access to a medium. Aloha systems work perfectlywell under a light load, but they cannot give any hard transmission guarantees, such asmaximum delay before accessing the medium or minimum throughput.  CSMA A popular MAC arbitration technique is the Carrier Sense Multiple Access(CSMA). In this technique, a node senses the medium before starting to transmit. If itsenses that some transmission is already underway, it defers its transmission. Twopopular extensions of the basic CSMA technique are the Collision Detection(CSMA/CD) and the Collision Avoidance (CSMA/CA) techniques. 69

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING 6. Describe Reservation Based Scheme A basic form of the reservation scheme is the RTS/CTS scheme. In an RTS/CTSscheme, a sender transmits an RTS (Ready To Send) packet to the receiver before theactual data transmission. On receiving this, the receiver sends a CTS (Clear to Send)packet, and the actual data transfer commences only after that. When the other nodessharing the medium sense the CS packet, they refrain from transmitting until thetransmission from the sending node is complete. MACA stands for Multiple Access Collision Avoidance. MACA solves thehidden/exposed terminal problems by regulating the transmitter power. A noderunning MACA requests to use the medium by sending an RTS to the receiver. Sinceradio signals propagate omni-directionally, every terminal within the sender’s radiorange will hear this and then refrain from transmitting. As soon as the receiver isready to receive data, it responds with CTS. UNIT - II MOBILE INTERNET PROTOCOL AND TRANSPORT LAYEROverview of Mobile IP – Features of Mobile IP – Key Mechanism in Mobile IP –route Optimization. Overview of TCP/IP – Architecture of TCP/IP- Adaptation ofTCP Window – Improvement in TCP Performance. KEY NOTES Overview of Mobile IP  Terminologies in Mobile IP  Tunneling and Encapsulation  Packet delivery Features of Mobile IP Transparency Compatibility Security Efficiency  Scalability Key Mechanism in Mobile IP  Discovering the care of address  Registering the care of address  Tunneling to the care of address Route Optimization  Messages transmitted in optimized mobile IP Overview of TCP/IP  TCP/IP protocol stack Architecture of TCP/IP  Application layer  Transport layer Internet layer 70

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Network access layer  Adaptation of TCP Window  A comparison of TCP/IP and ISO/OSI models  Improvement in TCP Performance  Traditional networks  Slow start  Congestion avoidance  Fast retransmit/fast recovery  TCP in Mobile Networks  TCP in single-hop wireless networks  Indirect TCP  Fast retransmission  Snooping TCP  Mobile TCP  Freeze TCP  TCP in multi-hop wireless networks PART-A 1. What is meant by Mobile IP? (Nov/Dec 2013) Mobile IP allows mobile computers to stay connected to the internet regardless oftheir location and without changing their IP address. Mobile IP is a standard protocolthat extends the internet protocol the internet protocol by making mobility transparentto applications and to higher level protocols like TCP. 2. Define Mobile Node (MN). A mobile node is hand held equipment with roaming capabilities. It can be a cellphone, personal digital assistant, laptop, etc. 3. Define Home Address (HA). The home address of a mobile device is the IP address assigned to the devicewithin its home network. The IP address on the current network is known as homeaddress. 4. Define Foreign Agent (FA). (Apr/May 2014) The foreign agent is a router in a foreign network that functions as the point ofattachment for a mobile node when it roams to the foreign network. The packets fromthe home agent are sent to the foreign node which delivers it to the mobile node. 5. Define Correspondent Node (CN). The home agent is a router on the home network serving as the anchor point forcommunication with the mobile node. It tunnels packets from a device on the internet,called a correspondent node (CN), to the roaming mobile node. 6. Define Care-of-Address (COA). (Nov/Dec 2014) It is the address that is used to identify the present location of a foreign agent. Thepackets sent to the MN are delivered to COA. The COA can be any of the following two types: 71

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING (i) Foreign agent COA: The COA is an IP address of foreign agent (FA). (ii) Co-located COA: When the mobile node (MN) acquires a temporary IP address, that address acts as the COA. 7. Define Home Agent (HA). It is located in home network and it provides several services for the MN. HAmaintains a location registry. The location registry keeps track of the node locationsusing the current care-of-address of the MN. 8. What is meant by agent discovery? During call establishment it is necessary for a mobile node to determine its foreignagent. This task is referred to as agent discovery. 9. What is meant by tunneling and encapsulation? (Nov/Dec 2013) Tunneling establishes a virtual pipe for the packets available between a tunnelentry and an endpoint. Tunneling is the process of sending a packet via a tunnel and itis achieved by a mechanism called encapsulation. Encapsulation refers to arranging apacket header and data in the data part of the new packet. 10. State some features of Mobile IP.Transparency: a mobile end-system should continue to keep its IP address and thereshould not be any disruption of communication after any movement. In other words,the IP address is to be managed transparently and there should not be any effect ofmobility on any ongoing communication.Efficiency and scalability: in the event of worldwide support, there can be a largenumber of mobile systems in the whole internet. This should neither result in largenumber of messages nor should it incur too much computational overhead. It shouldalso be scalable to support billions of moving hosts worldwide. 11. Describe security in Mobile IP. Security is very important in mobile IP as mobile nodes are often connected to theinternet via wireless links which are very vulnerable to security attacks. For example,during the registration procedure the home agent should be convinced that it is gettingthe authentic registration request from a mobile node. Mobile IP solves this problemby specifying a security association between the home agent and the mobile node. 12. What type of messages are transmitted in optimized Mobile IP (Nov ‘12) (i) Binding request: If a node wants to know the current location of a mobile node (MN), it sends a request to home agent (HA). (ii) Binding acknowledgement: On request, the node will return an acknowledgement message after getting the binding update message. (iii) Binding update: This is a message sent by HA to CN mentioning the correct location of MN. The message contains the fixed IP address of the mobile node and the care-of-address. The binding update can request for an acknowledgement. (iv) Binding warning: If a node decapsulates a packet for a mobile node (MN), but it is not the current foreign agent (FA), then this node sends a binding warning to the home agent (HA) of the mobile node (MN). 72

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING 13. Describe TCP protocol. TCP stands for Transmission Control Protocol. On the sending side, TCP isresponsible for breaking a message into small parts, adding sequence numbers andcertain other information and after this, making them known as segments. TCP passesthe segments to the lower layer protocol for transmission over the network. While at the receiver’s end, TCP assembles the segments when they arrive andreconstructs the message. TCP is a reliable protocol. Whenever a packet is lost orcorrupted during transmission, TCP detects it and requests the sender forretransmission. Thus, retransmission is used as the primary mechanism by TCP forreliable data delivery to the destination. 14. Describe Internet Protocol (IP). At the host machine of an application sending a message, IP is responsible forconstructing packets (also called datagrams) from the segments it receives from thetransport layer protocol by adding the destination host address and then passes theseon to the lower layer protocol for transmitting. On the receiver’s side, it deconstructsthe segments and then passes these to the transport layer protocol. 15. Discuss the functionalities of application layer in TCP/IP.The protocols at this application layer are used by applications to establishcommunication with other applications which may possibly be running on separatehosts. Example of application layer protocols are http, ftp and telnet. 16. Describe the functionalities of network access layer in TCP/IP. The functions of network access layer include encoding data and transmitting atthe signaling determined by the physical layer. It also provides error detection andpacket framing functionalities. 17. What is meant by slow start in TCP? The slow start mechanism is used when a TCP session is started. Instead ofstarting transmission at a fixed transmission window size, the transmission is startedat the lowest window size and then doubled after each successful transmission. 18. Define snooping TCP (S-TCP). (Apr/May 2011) The modified software at the base station is known as snoop. It monitors everypacket that passes through the TCP connection in both directions that is from MH toFH and vice versa. It buffers the TCP segments close to the MH. When congestiondetected during sending of packets from the FH to MH in the form of a duplicateacknowledgement or the timeout, it locally retransmits the packets to MH if it hasbuffered the packet and hides the duplicate acknowledgement. 19. What is meant by Mobile TCP(M-TCP)? (Apr/May 2009) This protocol for mobile cellular networks. The M-TCP protocol tries to avoid thesender window from shrinking or reverting to slow start when bit errors cause apacket loss, as is attempted in I-TCP and snooping TCP. 20. What is meant by freeze TCP? The basic idea in this scheme is to “freeze” the TCP senders’ streams, little beforea disconnection is to occur. This is done by artificially sending a “zero windowsadvertisement” informing the sender that the receiver cannot receive data at the 73

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGmoment. When the sender resumes its connectivity, the receiver can unfreeze thesender by sending the value of its actual receive window. PART-B 1. Explain the Overview of Mobile IP. (Apr/May 2010) Mobile IP allows mobile computers to stay connected to the internet regardless oftheir location and without changing their IP address. Mobile IP is a standard protocolthat extends the internet protocol the internet protocol by making mobility transparentto applications and to higher level protocols like TCP.  Mobile Node (MN): A mobile node is hand held equipment with roaming capabilities. It can be a cellphone, personal digital assistant, laptop, etc.  Home Address (HA): The home address of a mobile device is the IP address assigned to the devicewithin its home network. The IP address on the current network is known as homeaddress.  Foreign Agent (FA): The foreign agent is a router in a foreign network that functions as the point ofattachment for a mobile node when it roams to the foreign network. The packets fromthe home agent are sent to the foreign node which delivers it to the mobile node.  Correspondent Node (CN): The home agent is a router on the home network serving as the anchor point forcommunication with the mobile node. It tunnels packets from a device on the internet,called a correspondent node (CN), to the roaming mobile node.  Care-of-Address (COA): It is the address that is used to identify the present location of a foreign agent. Thepackets sent to the MN are delivered to COA. The COA can be any of the following two types: (iii) Foreign agent COA: The COA is an IP address of foreign agent (FA). (iv) Co-located COA: When the mobile node (MN) acquires a temporary IP address, that address acts as the COA.  Home Agent (HA): It is located in home network and it provides several services for the MN. HAmaintains a location registry. The location registry keeps track of the node locationsusing the current care-of-address of the MN.  Agent discovery: During call establishment it is necessary for a mobile node to determine its foreignagent. This task is referred to as agent discovery.  Tunneling and encapsulation: Tunneling establishes a virtual pipe for the packets available between a tunnelentry and an endpoint. Tunneling is the process of sending a packet via a tunnel and it 74

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGis achieved by a mechanism called encapsulation. Encapsulation refers to arranging apacket header and data in the data part of the new packet. 2. State Some Features Of Mobile IP.  Transparency: a mobile end-system should continue to keep its IP address and there should not be any disruption of communication after any movement. In other words, the IP address is to be managed transparently and there should not be any effect of mobility on any ongoing communication.  Efficiency and scalability: in the event of worldwide support, there can be a large number of mobile systems in the whole internet. This should neither result in large number of messages nor should it incur too much computational overhead. It should also be scalable to support billions of moving hosts worldwide.  Security in Mobile IP: Security is very important in mobile IP as mobile nodes are often connected to the internet via wireless links which are very vulnerable to security attacks. For example, during the registration procedure the home agent should be convinced that it is getting the authentic registration request from a mobile node. Mobile IP solves this problem by specifying a security association between the home agent and the mobile node.3. What type of messages are transmitted in optimized Mobile IP  Binding request: If a node wants to know the current location of a mobile node (MN), it sends a request to home agent (HA).  Binding acknowledgement: On request, the node will return an acknowledgement message after getting the binding update message.  Binding update: This is a message sent by HA to CN mentioning the correct location of MN. The message contains the fixed IP address of the mobile node and the care-of-address. The binding update can request for an acknowledgement.  Binding warning: If a node decapsulates a packet for a mobile node (MN), but it is not the current foreign agent (FA), then this node sends a binding warning to the home agent (HA) of the mobile node (MN).4. Explain the Overview of TCP/IP. TCP stands for Transmission Control Protocol. On the sending side, TCP isresponsible for breaking a message into small parts, adding sequence numbers andcertain other information and after this, making them known as segments. TCP passesthe segments to the lower layer protocol for transmission over the network. While at the receiver’s end, TCP assembles the segments when they arrive andreconstructs the message. TCP is a reliable protocol. Whenever a packet is lost orcorrupted during transmission, TCP detects it and requests the sender forretransmission. Thus, retransmission is used as the primary mechanism by TCP forreliable data delivery to the destination. 75

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Internet Protocol (IP): At the host machine of an application sending a message, IP is responsible forconstructing packets (also called datagrams) from the segments it receives from thetransport layer protocol by adding the destination host address and then passes theseon to the lower layer protocol for transmitting. On the receiver’s side, it deconstructsthe segments and then passes these to the transport layer protocol.  Functionalities Of Application Layer In TCP/IP:The protocols at this application layer are used by applications to establishcommunication with other applications which may possibly be running on separatehosts. Example of application layer protocols are http, ftp and telnet.  Functionalities Of Network Access Layer In TCP/IP: The functions of network access layer include encoding data and transmitting atthe signaling determined by the physical layer. It also provides error detection andpacket framing functionalities.  Slow Start In TCP: The slow start mechanism is used when a TCP session is started. Instead ofstarting transmission at a fixed transmission window size, the transmission is startedat the lowest window size and then doubled after each successful transmission.  Snooping TCP (S-TCP): The modified software at the base station is known as snoop. It monitors everypacket that passes through the TCP connection in both directions that is from MH toFH and vice versa. It buffers the TCP segments close to the MH. When congestiondetected during sending of packets from the FH to MH in the form of a duplicateacknowledgement or the timeout, it locally retransmits the packets to MH if it hasbuffered the packet and hides the duplicate acknowledgement.  Mobile TCP(M-TCP): This protocol for mobile cellular networks. The M-TCP protocol tries to avoid thesender window from shrinking or reverting to slow start when bit errors cause apacket loss, as is attempted in I-TCP and snooping TCP.  Freeze TCP: The basic idea in this scheme is to “freeze” the TCP senders streams, little beforea disconnection is to occur. This is done by artificially sending a “zero windowsadvertisement” informing the sender that the receiver cannot receive data at themoment. When the sender resumes its connectivity, the receiver can unfreeze thesender by sending the value of its actual receive window. 5. Draw the Architecture of TCP/IP.  Application layer  Transport layer  Internet layer  Network access layer 76

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING UNIT – III MOBILE TELECOMMUNICATION SYSTEMGlobal System for Mobile Communication (GSM) – General Packet Radio Service(GPRS) – Universal Mobile Telecommunication System (UMTS) KEY NOTES  Global System for Mobile Communication (GSM)  GSM services  Bearer services  Tele services  Supplementary services  System Architecture of GSM  Radio subsystem  Network and switching subsystem  Operation subsystem  GSM Security  Authentication  Confidentiality  Anonymity  General Packet Radio Service (GPRS)  GPRS services  GPRS Architecture  Universal Mobile Telecommunication System (UMTS)  UMTS network architecture PART-A 1. Describe bearer services in GSM. (Apr/May 2010)Bearer services give the subscribers the capability to send and receive data to/fromremote computers or mobile phones. For his reason, bearer services are also known asdata services. These services also enable the transparent transmission of data betweenGSM and other networks like PSTN, ISDN, etc. at rates from 300 bps to 9600 bps.These services are implemented on the lower0three layers of the OSI reference model. 2. How to classify the tele services in GSM? GSM provides both the voice-oriented tele services and the non-voice tele services. Voice-oriented services are telephony and emergency number Non-voice tele services are short message services and Fax. 3. State the functionalities of supplementary services. GSM provides certain supplementary services such as user identification, callredirection and forwarding of ongoing calls. In addition, standard ISDN features suchas ‘close user groups’ and ‘multiparty’ communication are available. 77

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING 4. How to classify the GSM main subsystems?A GSM system consists of three main subsystems: (i) Radio Subsystem (RSS) (ii) Networking and Switching Subsystem (NSS) (iii)Operation Subsystem (OSS) 5. Describe Mobile Station (MS). A mobile station (MS) or cell phone contains two major components: thesubscriber identity module (SIM) and the mobile device. The SIM is a removablesmart card. Each mobile device has a unique identifier that is known as its IMEI(International Mobile Equipment Identity). 6. What is meant by Base Station Controller (BSC)? (Nov/Dec 2013) A BSC manages the radio resource of the BTSs in the sense that it assignsfrequency and time slots for all MSs in the area. It also manages the handoff from oneBTS to another within the BSS. The BSC also multiplexes the radio channels onto thefixed network connection to the Mobile Switching Centre (MSC). 7. What is meant by Mobile Switching Centre (MSC)? A MSC can be considered to form the heart of a GSM network. An MSC sets upconnections to other MSCs and to other networks such as Public Data Network(PDN). An MSC is responsible for the connection setup, connection release, and callhandoff to other MSCs. A Gateway MSC (GMSC) is responsible for gatewayfunctions, while a customer roams to other networks. It also performs certain othersupplementary services such as call forwarding, multiparty calls, etc. 8. Explain about Home Location Register (HLR). A HLR stores in a database important information that is specific to eachsubscriber. The information contains subscriber’s IMSI, pre/post paid, user’s currentlocation, etc. 9. How to update the Visitor Location Register (VLR)? (Nov/Dec 2010) It is essentially a temporary database that is updated whenever a new MS enters itsarea by roaming. The information is obtained from the corresponding HLR database.The function of the VLR is to reduce the number of queries to the HLR and make theuser feel as if he were in his home network. 10. Explain the use of Authentication Centre (AuC). It protects against intruders targeting the air interface. The AuC stores informationconcerned with security features such as user authentication and encryption. The AuCis related to the HLR. 11. What is the usage of Equipment Identity Register (EIR)? It is essentially a database that is used to track handsets using the IMEI. It helps toblock calls from stolen, unauthorized or defective mobiles. 12. Explain the term authentication in GSM security. (Nov/Dec 2012) The purpose of authentication is to protect the network against unauthorized use.In the GSM context, it helps protect the GSM subscribers by denying the possibilityfor intruders to impersonate authorized users. A GSM network operator can verify the 78

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGidentity of the subscriber, making it highly improbable to clone someone else’smobile phone identity. Authentication can be achieved in a simple way by using a password such asPersonal Identification Number (PIN). This method is not very secure in GSMnetworks as an attacker can ‘listen’ the PIN and easily break the code. 13. What is type of services in GPRS?GPRS offers end-to-end packet-switched data transfer services which can becategorized into the following two type: (i) Point-to-Point (PTP) service (ii) Point-to-Multipoint (PTM) service. 14. Give the new network elements in GPRS. GPRS architecture introduces two new network elements, called GPRS SupportNode (GSN) and the Gateway GPRS Support Node (GGSN). A GSN is essentially arouter. All GSNs are integrated into a standard GSM architecture. The GGSN is theinterworking unit between the GPRS network and the external packet data network(PDN). The GGSN contains routing information for GPRA users, 0erforms addressconnection and tunnels data to a user through encapsulation. 15. Howmany elements are divided in UMTS network architecture? The UMTS network architecture can be divided into three main elements. (i) User Equipment (UE) (ii) Radio Network Subsystem (RNS) (iii)Core Network PART-B 1. Describe the Services in GSM. (Nov/Dec 2013)  Bearer services in GSM Bearer services give the subscribers the capability to send and receive data to/from remote computers or mobile phones. For his reason, bearer services are also known as data services. These services also enable the transparent transmission of data between GSM and other networks like PSTN, ISDN, etc. at rates from 300 bps to 9600 bps. These services are implemented on the lower0 three layers of the OSI reference model.  Tele services in GSM: GSM provides both the voice-oriented tele services and the non-voice teleservices. Voice-oriented services are telephony and emergency number Non-voice tele services are short message services and Fax.  Functionalities of supplementary services: GSM provides certain supplementary services such as user identification, callredirection and forwarding of ongoing calls. In addition, standard ISDN features suchas ‘close user groups’ and ‘multiparty’ communication are available. 79

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING 2. Explain classification of subsystem in GSM. (Nov/Dec 2015, Apr/May 2015) Classify The GSM Main Subsystems: A GSM system consists of three main subsystems: (iv)Radio Subsystem (RSS) (v) Networking and Switching Subsystem (NSS) (vi)Operation Subsystem (OSS)  Mobile Station (MS): A mobile station (MS) or cell phone contains two major components: thesubscriber identity module (SIM) and the mobile device. The SIM is a removablesmart card. Each mobile device has a unique identifier that is known as its IMEI(International Mobile Equipment Identity).  Base Station Controller (BSC): A BSC manages the radio resource of the BTSs in the sense that it assignsfrequency and time slots for all MSs in the area. It also manages the handoff from oneBTS to another within the BSS. The BSC also multiplexes the radio channels onto thefixed network connection to the Mobile Switching Centre (MSC).  Mobile Switching Centre (MSC): A MSC can be considered to form the heart of a GSM network. An MSC sets upconnections to other MSCs and to other networks such as Public Data Network(PDN). An MSC is responsible for the connection setup, connection release, and callhandoff to other MSCs. A Gateway MSC (GMSC) is responsible for gatewayfunctions, while a customer roams to other networks. It also performs certain othersupplementary services such as call forwarding, multiparty calls, etc.  Home Location Register (HLR): A HLR stores in a database important information that is specific to eachsubscriber. The information contains subscriber’s IMSI, pre/post paid, user’s currentlocation, etc.  Visitor Location Register (VLR): It is essentially a temporary database that is updated whenever a new MSenters its area by roaming. The information is obtained from the corresponding HLRdatabase. The function of the VLR is to reduce the number of queries to the HLR andmake the user feel as if he were in his home network.  Authentication Centre (AuC): It protects against intruders targeting the air interface. The AuC stores informationconcerned with security features such as user authentication and encryption. The AuCis related to the HLR.  Equipment Identity Register (EIR): It is essentially a database that is used to track handsets using the IMEI. It helps toblock calls from stolen, unauthorized or defective mobiles.  Authentication in GSM security: The purpose of authentication is to protect the network against unauthorizeduse. In the GSM context, it helps protect the GSM subscribers by denying the 80

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGpossibility for intruders to impersonate authorized users. A GSM network operatorcan verify the identity of the subscriber, making it highly improbable to clonesomeone else’s mobile phone identity. Authentication can be achieved in a simple way by using a password such asPersonal Identification Number (PIN). This method is not very secure in GSMnetworks as an attacker can ‘listen’ the PIN and easily break the code. 3. Explain the types of services in GPRS? GPRS offers end-to-end packet-switched data transfer services which can becategorized into the following two type: (iii)Point-to-Point (PTP) service (iv)Point-to-Multipoint (PTM) service. The New Network Elements In GPRS: GPRS architecture introduces two new network elements, called GPRSSupport Node (GSN) and the Gateway GPRS Support Node (GGSN). A GSN isessentially a router. All GSNs are integrated into a standard GSM architecture. TheGGSN is the interworking unit between the GPRS network and the external packetdata network (PDN). The GGSN contains routing information for GPRA users,0erforms address connection and tunnels data to a user through encapsulation. 4. How to divide the network element in UMTS architecture? Network elements are divided in UMTS network architecture: The UMTS network architecture can be divided into three main elements. (iv)User Equipment (UE) (v) Radio Network Subsystem (RNS) (vi)Core Network UNIT – IV MOBILE AD-HOC NETWORKSAd-Hoc Basic Concepts – Characteristics – Applications – Design Issues – Routing –Essential of Traditional Routing Protocols –Popular Routing Protocols – VehicularAd Hoc networks ( VANET) – MANET Vs VANET – Security KEY NOTES  Ad-Hoc Basic Concepts  How is an ad-hoc network set up without the infrastructure support?  Why is routing in a MANET a complex task?  Characteristics  Lack of fixed infrastructure  Dynamic topologies  Bandwidth constrained, variable capacity links  Energy constrained operation  Increased vulnerability  Other characteristics  MANET operational constraints 81

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Applications  Communication among portable computers  Environmental monitoring  Military  Emergency applications  Design Issues  Network size and node density  Connectivity  Network topology  User traffic  Operational environment  Energy constraint  Routing  Routing in MANETs Vs Routing in Traditional networks  A classification of Unicast MANET routing protocols  Proactive protocols  Reactive protocols  Hybrid routing protocols  Essential of Traditional Routing Protocols  Link state protocols  Distance vector protocols  Popular Routing Protocols  Destination-sequenced distance vector routing protocol  Dynamic Source Routing Protocol  Ad-hoc on-demand distance vector  Zone routing protocol  Multicast routing protocols for MANET  Vehicular Ad Hoc networks ( VANET)  MANET Vs VANET  Security  Characteristics of secure adhoc networks PART-A 1. What is meant by MANET? (Nov/Dec 2015)Mobile ad hoc networks are realized through short-lived links among the mobiledevices. Such temporary or ad hoc networks that are established and maintained onthe fly and work without the support of any form of fixed infrastructure such as a basestation, are known as Mobile Ad hoc NETworks (MANETs) 2. Give some characteristics of MANETs.There are several characteristics that distinguish a MANET from an infrastructurebased network. Naturally, these characteristics must be carefully considered while 82

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGtrying to improvise new network protocols or extend the traditional network protocolsfor use in a MANET. A few of these important characteristics of MANETs are, (i) Lack of fixed infrastructure (ii) Dynamic topologies (iii)Bandwidth constrained, variable capacity links (iv)Energy constrained operation (v) Increased vulnerability 3. Give some applications of MANETs. The applications are, (i) Communication among portable computers (ii) Environmental monitoring (iii)Military (iv)Emergency applications 4. What are the two parameters are considered in MANETs design? Network size and node density are the two parameters of a MANET that need tobe considered while designing an appropriate routing protocol for a network. Networksize refers to the geographical coverage area of the network and network densityrefers to the number of nodes present per unit geographical area. For larger networks,clustering is essential to keep the communication overheads low. The cluster size aswell as a specific clustering solution for a network would, to a large extent, depend onnode density. 5. What is meant by user traffic in MANET? The design of a MANET is carried out primarily based on the anticipated nodedensity, average rate of node movements, and the expected traffic. The traffic in anetwork can be of various types. A network protocol should leverage thecharacteristics of specific traffic types that are expected to improve its performance.The common traffic types are the following  Bursty traffic  Large packets sent periodically  Combination of the above two types of traffic 6. How to send a packet in MANET? (i) Forward the packet to the next node (hop). (ii) While forwarding the packet, the sender needs to ensure that:  The packet moves towards its destination  The number of hops/path length is minimized  Delay is minimized  The packet loss is minimized  The packet does not move around the network endlessly 7. What is meant by link state in LSP? The term link state denotes the state of a connection of one router with one of itsneighbours. A neighbor of a router is one with which it can directly communicatewithout taking any help from the intervening routers. Each router determines its local 83

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGconnectivity information, and floods the network with this information with a linkstate advertisement. 8. Which type of messages will store in link state advertisement?The link state advertisement message contains: (i) The identity of the router originating the message (ii) The identities of all its neighbours (iii)The delays along various links to its neighbours (iv)A unique sequence number, which is formed by increasing the count every time the router forms a new ink state advertisement. 9. Define DSDV. (Apr/May 2009) Destination-Sequenced Distance-Vector Routing (DSDV) is an importantMANET routing protocol. It is based on the table driven approach to packet routing. 10. Explain the steps in operations of DSDV.The important steps in the operation of DSDV are summarized below: (i) Each router (node) in the network collects route information from all its neighbours (ii) After gathering information, the node determines the shortest path to the destination based on the gathered information (iii)Based on the gathered information, a new routing table is generated (iv)The router broadcasts this table to its neighbours. On receipt by neighbours, the neighbor nodes recomputed their respective routing tables. (v) This process continues till the routing information becomes stable. 11. What are two phases in DSR? DSR works in two phases: (i) Route discovery –It allows any host to dynamically discover the route to any destination in the ad hoc network. When a node has a data packet to send, it first checks its own routing cache. (ii) Route maintenance – Route maintenance is the process of monitoring the correct operation of a route in use and taking any corrective action when needed. 12. Describe AODV. (Nov/Dec 2015) The route discovery and route maintenance activities in AODV are very similar tothose for the DSR protocol. AODV does make use of hop-by-hop routing, sequencenumbers and beacons. The node that needs a route to a specific destination generates aroute request. The route request is forwarded by intermediate nodes which also learn areverse route from the source to themselves. 13. What is meant by tree based protocol? Tree based schemes establish a single path between any two nodes in the multicastgroup. These schemes require minimum number of copies per packet to be sent alongthe branches of the tree. Hence, they are bandwidth efficient. 14. Explain VANETs. A Vehicular Ad hoc NETwork (VANET) is a special type of MANET in whichmoving automobiles form the nodes of the network. VANETs were initiallyintroduced for vehicles of police, fire brigades and ambulances for safe travelling on 84

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGroad. In this network, a vehicle communicates with other vehicles that are within arange of about 100 to 300 metres. 15. Give some security causes in MANET. A few important characteristics of ad hoc networks that can be exploited to cause security vulnerabilities are the following: (i) Lack of physical boundary (ii) Low power RF transmissions (iii) Limited computational capabilities (iv) Limited power supply PART-B 1. What are design issues in MANET?  Network size and node density  Connectivity  Network topology  User traffic  Operational environment  Energy constraint 2. Briefly Explain about MANET? Mobile ad hoc networks are realized through short-lived links among the mobiledevices. Such temporary or ad hoc networks that are established and maintained onthe fly and work without the support of any form of fixed infrastructure such as a basestation, are known as Mobile Ad hoc NETworks (MANETs).  Characteristics Of MANETs.: There are several characteristics that distinguish a MANET from an infrastructurebased network. Naturally, these characteristics must be carefully considered whiletrying to improvise new network protocols or extend the traditional network protocolsfor use in a MANET. A few of these important characteristics of MANETs are, (i) Lack of fixed infrastructure (ii) Dynamic topologies (iii)Bandwidth constrained, variable capacity links (iv)Energy constrained operation (v) Increased vulnerability  Applications of MANETs: (i) Communication among portable computers (ii)Environmental monitoring (iii)Military (iv)Emergency applicationsTwo parameters are considered in MANETs design: Network size and node density are the two parameters of a MANET that need tobe considered while designing an appropriate routing protocol for a network. Networksize refers to the geographical coverage area of the network and network density 85

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGrefers to the number of nodes present per unit geographical area. For larger networks,clustering is essential to keep the communication overheads low. The cluster size aswell as a specific clustering solution for a network would, to a large extent, depend onnode density.  User traffic in MANET: The design of a MANET is carried out primarily based on the anticipated nodedensity, average rate of node movements, and the expected traffic. The traffic in anetwork can be of various types. A network protocol should leverage thecharacteristics of specific traffic types that are expected to improve its performance.The common traffic types are the following  Bursty traffic  Large packets sent periodically  Combination of the above two types of traffic 3. How to send a packet in MANET? (iii)Forward the packet to the next node (hop). (iv)While forwarding the packet, the sender needs to ensure that:  The packet moves towards its destination  The number of hops/path length is minimized  Delay is minimized  The packet loss is minimized  The packet does not move around the network endlessly  Protocols in MANET:  Link state in LSP: The term link state denotes the state of a connection of one router with one of itsneighbours. A neighbor of a router is one with which it can directly communicatewithout taking any help from the intervening routers. Each router determines its localconnectivity information, and floods the network with this information with a linkstate advertisement.  Link state advertisementThe link state advertisement message contains: (i)The identity of the router originating the message (ii)The identities of all its neighbours (iii)The delays along various links to its neighbours (iv)A unique sequence number, which is formed by increasing the count everytime the router forms a new ink state advertisement. 4. Describe DSDV. (Nov/Dec 2013) Destination-Sequenced Distance-Vector Routing (DSDV) is an importantMANET routing protocol. It is based on the table driven approach to packet routing.The steps in operations of DSDV:The important steps in the operation of DSDV are summarized below: (i)Each router (node) in the network collects route information from all itsneighbours 86

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING (ii)After gathering information, the node determines the shortest path to the destination based on the gathered information (iii)Based on the gathered information, a new routing table is generated (iv)The router broadcasts this table to its neighbours. On receipt by neighbours, the neighbor nodes recomputed their respective routing tables. (v)This process continues till the routing information becomes stable.5. Describe Dynamic Source Routing Protocol(DSR). (Nov/Dec 2013)Two phases in DSR: DSR works in two phases: (i) Route discovery –It allows any host to dynamically discover the route to any destination in the ad hoc network. When a node has a data packet to send, it first checks its own routing cache. (ii) Route maintenance – Route maintenance is the process of monitoring the correct operation of a route in use and taking any corrective action when needed. The route discovery and route maintenance activities in AODV are very similar to those for the DSR protocol. AODV does make use of hop-by-hop routing, sequence numbers and beacons. The node that needs a route to a specific destination generates a route request. The route request is forwarded by intermediate nodes which also learn a reverse route from the source to themselves.Tree based protocol:Tree based schemes establish a single path between any two nodes in the multicastgroup. These schemes require minimum number of copies per packet to be sent alongthe branches of the tree. Hence, they are bandwidth efficient.6. Explain briefly about VANETs. A Vehicular Ad hoc NETwork (VANET) is a special type of MANET inwhich moving automobiles form the nodes of the network. VANETs were initiallyintroduced for vehicles of police, fire brigades and ambulances for safe travelling onroad. In this network, a vehicle communicates with other vehicles that are within arange of about 100 to 300 metres.  Security causes in VANET: A few important characteristics of ad hoc networks that can be exploited to cause security vulnerabilities are the following: (i)Lack of physical boundary (ii)Low power RF transmissions (iii)Limited computational capabilities (iv)Limited power supply7. Explain the Popular Routing Protocols in MANET.  Destination-sequenced distance vector routing protocol  Full dump  Operation of DSDV  Dynamic Source Routing Protocol  Route discovery 87

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Route maintenance  Ad-hoc on-demand distance vector  Route request  Route reply  Zone routing protocol  Multicast routing protocols for MANET  Tree based protocol  Mesh based protocol UNIT – V MOBILE PLATFORMS AND APPLICATIONSMobile Device Operating Systems – Special Constrains & Requirements –Commercial Mobile Operating Systems – Software Development Kit: iOS, Android,BlackBerry, Windows Phone – M-Commerce – Structure – Pros & Cons – MobilePayment System – Security Issues. KEY NOTES  Mobile Device Operating Systems  Special Constrains & Requirements  Special constraints  Limited memory  Limited screen size  Miniature keyboard  Limited processing power  Limited battery power  Limited and fluctuating bandwidth of the wireless medium  Special service requirements  Support for specific communication protocols  Support for a variety of input mechanisms  Compliance with open standards  Extensive library support  Commercial Mobile Operating Systems  Software Development Kit: iOS  Android  Application layer  Application framework  Libraries and runtime  Kernel  BlackBerry  Windows Phone  M-Commerce  Business-to- consumer applications 88

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Business-to-business applications  Structure  Mobile devices  Mobile middleware  Network  Host computers  Pros & Cons  Mobile Payment System  Mobile payment schemes  Bank account based M-payment  Credit card based M-payment  Micropayment  Security Issues. PART-A 1. What is meant by Mobile Operating system? A mobile operating system, also called a mobile OS, is an operating system that isspecifically designed to run on mobile devices such as mobile phones, smartphones,PDAs, tablet computers and other handheld devices. The mobile operating system isthe software platform on top of which other programs, called application programs,can run on mobile devices. 2. Give the special constraints of Mobile Operating system.  Limited memory  Limited screen size  Miniature keyboard  Limited processing power  Limited battery power  Limited and fluctuating bandwidth of the wireless medium 3. Give the special service requirements of Mobile Operating system.  Support for specific communication protocols  Support for a variety of input mechanisms  Compliance with open standards  Extensive library support 4. Explain about windows mobile. Windows mobile operating system was developed to be suitable for use on multiple vendor platforms, Microsoft defined a hardware specification for hand- held computers that can run its windows mobile operating system in order to simplify the design of the operating system and to reduce the number of versions of operating system. Windows mobile classic operating systems support touch screen-based user interface but do not support any phone capability. 89

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING 5. Give the important features of Windows Mobile OS. A few important features of the windows mobile OS are the following:  The graphics/window/event manager (GWE) component handles all input and output.  Provides a virtual memory management.  Supports security through the provision of a cryptographic library.  Application development is similar to that in the Win32 environment. 6. What is meant by iOS? iOS is Apple's proprietary mobile operating system (OS) for its handheld devices, such as the iPhone, iPad and iPod Touch. The operating system is based on the Macintosh OS X. Designed for use with Apple’s multi-touch devices, iOS supports input throughdirect manipulation. The system responds to various user gestures, such as pinching,tapping and swiping. 7. Give the important features of iOS. A few important features of the iOS are the following:  Integrated search support enables simultaneous search through files, media, applications and email.  Gesture recognition supports, for example, shaking the device to undo the most recent action.  Google Maps direction services.  Push email.  Safari mobile browser.  Integrated camera and video.  Integrated media player.  Direct access to the Apple Store’s catalogue of applications, music, podcasts, television shows and movies.  Compatibility with Apple’s cloud service, iCloud. 8. What is meant by android? Android is the name of the mobile operating system made by American company;Google. It most commonly comes installed on a variety of smartphones and tabletsfrom a host of manufacturers offering users access to Google’s own services likeSearch, YouTube, Maps, Gmail and more. This means you can easily look for information on the web, watch videos, searchfor directions and write emails on your phone, just as you would on your computer,but there’s more to Android than these simple examples. 9. What is meant by blackberry? The BlackBerry is a smartphone OS that is widely used in the enterprise for its wireless email handling capability. 10. What is meant by M-commerce? M-commerce (mobile commerce) is the buying and selling of goods and servicesthrough wireless handheld devices such as cellular telephone and personal digital 90

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERINGassistants (PDAs). Known as next-generation e-commerce, m-commerce enablesusers to access the Internet without needing to find a place to plug in. The emergingtechnology behind m-commerce, which is based on the Wireless Application Protocol(WAP), has made far greater strides in Europe, where mobile devices equipped withWeb-ready micro-browsers are much more common than in the United States. 11. Give the advantages of M-commerce.Advantages of Mobile Commerce:  This M-Commerce is beneficial for both type of businesses large scale and small scale. The mobile users increase day by day, so through M-Commerce your business gets large and growing market place for wild range of goods and services.  Cover wild distance : Mobile is the only technology which is now become necessary for any person in social and business life than computers. So, it is easy to reach users through M-Commerce.  Consumer deals : As more users use M-Commerce, there are lots of companies use M-Commerce site to reach them by giving different and better deals in comparison of their competitor.  Savings : Companies try to reach to the consumer directly through M- Commerce, so users have no need to go far to the store physically and at the end it saves user’s time and money.  Easy to use : There is no need of skilled consumer. Buyers can have look thousands of items on their cell phones and there is no need of online checkout process. 12. Give the disadvantages of M-commerce.  Every invention has its own merits and demerits. It is applicable in this M- Commerce business also.  Smart phone limitation : Mobile has no big screen like desktop or laptops, so sometimes users tired to navigate more and more to choose just one item from thousands. It affects shopping rates.  Habituate : Every new technology has some problem at the starting phase. Here M-Commerce is new application, so sometimes people avoid to change which are rapidly change. As they are habituate to buy products from eCommerce.  Risk factor : Each business has its own risk. Same Moblie commerce is the growing field and a lot of investment in this field is become risky. Because technology change day by day. Moreover, there less security in wireless network, so in data transfer hacking chances are more.  Connectivity : Moblie commerce needs high speed connectivity of 3G. Otherwise it is become hectic for user to go through entire product purchase process. 91

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING 13. What is meant by Mobile payment systems? Mobile payment (m-payment) is a point-of-sale (PoS) transaction made or received with a mobile device. Mobile payments are gaining popularity with consumers not only for their convenience but also for their security, because with many types of mobile PoS systems, credit card data is not saved on the merchant's PoS terminal. The consumer's mobile device actually becomes a security token that generates a random code for each transaction. Depending upon the technology used, the token may be transmitted over the air (OTA) or entered manually into a keypad by the consumer. 14. Give the types of M-payment schemes. Three popular types of M-payment schemes are currently being used:  Bank account based M-payment  Credit card based M-payment  Micropayment PART-B 1. Explain detail about Mobile Operating Systems and Special Constrains & Requirements of mobile OS An Operating System, or OS, is the master software that is run on a computeror smartphone that allows it to run other applications developed for that platform.Common mobile phone operating systems include Windows Mobile, the Symbian OS,Palm OS, and Linux. Also known as: \"OS\"A mobile operating system (or mobile OS)is an operating system for smartphones, tablets, PDAs, or other mobile devices.(i)Quality of Service constraints • Technical restrictions and practical considerations ─ difficulties in mobile device uninterrupted operations • Maintaining quality of service along with the provisioning of seamlessaccess to all users.(ii)Accessibility constraints • Smart labels on packages limited access ─ transmitted signals low power • Labels can only be read from very short ranges RFID access limited to ranges within line of sight • RFID transmissions require hotspots close by due to low transmitted signalstrength. (A hotspot is an access point an interface for mobile systems, sensingsystems, and embedded systems to connect to a mobile network, wireless LAN, or theInternet.)(iii)Range Constraints: • Signal strength inversely proportional to the square of the distance 92

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING • Degradation of signal quality due to reflection, scattering, and diffractionAccess range limited to the range up to which the signal strength is such that it can beseparated from the noise • Up to which multi-path delays can be compensated for by digital signalprocessing techniques to restore signal quality(iv)Connectivity: • Connectivity loss or intermittent connectivity in certain situations • The atmospheric conditions changes in environment affect signal strength • Water attenuation of UHF and near microwave • For example, in the event of heavy rain, there may be complete loss ofconnectivity(v) Security Constraints: • Unsolicited advertisements and unwanted messages • Virus attacks • Hackers render it functionless or threaten integrity and security of the datastored on the device • Noise signals transmitted by an attacker can jam a mobile device Repeatedtransmission of unwanted signals by an attacker can drain the resources of the device • Energy resources depleted fast when computations are forced andauthentication algorithms are run repeatedly(vi)Mobility constraints: • Non-availability of an access point or base station • Infrastructural issues • No base stations or Wi-Fi hotspots providing connectivity and access to theInternet to sensors, labels, automotive systems, RFID tags, and cell phones Use ofdifferent standards in different regions limits the operability • A GSM phone may not be operable in all continents hence hampering globalroaming for the user • Some service providers may not be able to provide connectivity in all partsof the country or in other continents, etc.(vii) Energy Constraints in Devices • Limited energy in battery • Battery size and power limited due to considerations such as size, weight,and bulk of mobile devices •The devices need to be recharged after short periods of time. In this wayenergy availability also limits device mobility. •Some devices such as smart cards, smart labels, remote sensors, andactuators do not even have a battery of their own. They derive their energy from theradiation received from a wireless source in vicinity. Such devices, therefore, requirethese sources to operate Some devices such as smart cards, smart labels, remotesensors, and actuators do not have a battery of their own. • They derive their energy from the radiation received from a wireless sourcein vicinity. 93

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING • Such devices require these sources(viii)Bandwidth Constraints • Limited by the frequency spectrum that a regulator allots to a serviceprovider • The service must use the frequency spectrum allotted to it in an efficientmanner Multiplexing and coding techniques help in achieving efficient transmission. • The technology in use also limits the spectrum efficiency • For example, CDMA has higher spectrum efficiency as compared to GSM. 2. Describe Software Development kit.  Smartphones Developing Mobile Applications  Android  iOS  BlackBerry  Windows Mobile.  Cell phones:  low-end ”feature phones”  high-end ”smartphones  Smartphone Features  More powerful than feature phone  With more device capabilities  Smartphone as a new PC  Typically cheaper than computers  More convenient because of their portability  Will perform many of the routine tasks currently on a desktop/laptop  The center of gravity of the software industry will be mobilized.  Terminology  Integrated Development Environment (IDE)  Application Programming Interface (API)  Software Development Kit (SDK)  Native Development Kit (NDK) 3. Explain detail about Mobile Commerce. Mobile Commerce defines as an ability to access an IT-System whilst movingfrom one place to the other using a mobile device and carry out transactions andtransfer information wherever and whenever needed to. In our context, by mobiledevice , we refer to a cell phone device. M-commerce does not have a precise or fixeddefinition. M-commerce and its definition vary from one person to the other. Fromwhat we have noticed, m-commerce can be seen and understood in many ways anddifferently by various people.  M-commerce can be seen as means of selling and purchasing of goods and services using mobile communication devices such as cellular phones, PDA s etc, which are able to connect to the Internet through wireless channels and interact with e-commerce systems . 94

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  M-commerce can be referred to as an act of carrying-out transactions using a wireless device .  It is understood as a data connection that results in the transfer of value in exchange for information, services or goods .  It can also bye seen as a natural extension of e-commerce that allows users to interact with other users or businesses in a wireless mode, anytime/anywhere.  It can be perceived to be any electronic transaction or information interaction conducted using a mobile device and mobile network thereby guaranteeing customers virtual and physical mobility , which leads to the transfer of real or perceived value in exchange for personalized, location-based information, services, or goods  M-commerce can also be seen and referred to as wireless commerce  It is any transaction with a monetary value that is conducted via a mobile telecommunications network .  As it can be noticed from above, the definition of m-commerce differs from one person to the other. We have a view and an argument that m-commerce does not necessarily have to involve valued or monetary transactions. We see m-commerce as any transaction, information transfer and interchange carried- out in the mobile environment. Though there are many definitions of m- commerce, we accept the one given which views m-commerce as transactions or information interaction using a mobile device and mobile network to guarantee customer and users physical mobility. Even though we accept it, this definition does not fully fit our context; hence we have given our definition of m-commerce. 4. Describe M-Commerce Architecture M-commerce structural design or architecture is a three-tier type ofarchitecture. It consists of or is divided into:  Front-End (client) The piece of application that runs on the mobile device or the mobile device itself,  Middleware (server) is the software server running on the desktop workstation, which contains the business logic of the system. The actual desktop workstation or computer on which the server software is installed can itself be seen as a server  Back-End (database) - can refer to the database server (i.e. Database Management System (DBMS)) installed on a particular computer or can refer to that particular computer itself. When defining these tiers, someone can be referring to the software or hardware part of them. However, for the client to be complete and be able to do the job of being a client has to have both the software and the hardware. The same applies to the other tiers as well. The diagram below shows the m-commerce structure and layout. 95

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING M-Commerce ArchitectureThe above diagram shows: Numbers 1(a), 1(b) and 1(c) - show cell phone devices which are used toaccess the m-commerce systems. They are basically the front end tiers (or clients) inthe m-commerce architecture. Numbers 2(a), 2(b) and 2(c) show the base station whose function is toforward and route the signals to the intended destination. Number 3 shows the SMS gateway which is used to bridge the systems thatcommunicate via the SMS platform with their mobile clients, i.e. the cell phonedevices. It is meant for communications that are done via text messages between thecell phone and the system. Number 4 - shows the Wireless Applications Protocol (WAP) gateway whichconverts WAP requests from the cell phone to HTTP requests and converts HTTPresponses from the web server to WAP responses. Number 5 - shows the web server which serves as the middleware in the M-commerce architecture. The middleware (web server) contains or keeps the businesslogic of the M-commerce system. Number 6 shows the database server which serves as a back-end in the M-commerce architecture. The above diagram shows the structural design of m-commerce systems.Customers or users access these systems via their cell phones (as show in 1(a)-(c)).The user accessing the server using the GPRS enabled cell phone, (in 1(c)) makesdirect. HTTP connections to the IP-based web server without going through the WAPgateway. This is due to the fact that GPRS simulates the TCP/IP network principlesand concepts 96

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING6. Describe Security Issues in Mobile Payment System For widespread use and customer acceptance of m-payment services, bothperceived and technical levels of security should be high. For customers, privacyshould not be compromised and there should be no possibility of financial losses. Forbusinesses, customer authentication is important. As per the general framework of anysecure messaging system - confidentiality, integrity, non-repudiation andauthentication should be guaranteed by the m-payment services. The transport layersecurity offered by GSM/CDMA networks sufficiently guarantees confidentiality(that messages cannot be read by anyone else) and message integrity (the assurancethat the message has not been altered in transit). Authentication (identifies the authorof the transaction) and non-repudiation (makes sure that any of the users in the systemcannot later deny the message they sent) can only be guaranteed with the help ofwireless public key infrastructure (WPKI) and digital certificates. Hassinen,Hyppönen and Trichina (2007) suggest that secure mobile payment transactions canbe implemented using existing national public key infrastructure, which isindependent of financial institutions, mobile network operators and mobile paymentapplication service providers but can be used by all of them. Their proposedtechnological solution to provide secure mobile payment transaction is brieflydescribed below.  Public Key Infrastructure and SIM cards Every user of the system is listed in a publicly available directory. Arunawould like to send a message to another user Bob. Aruna first obtains Bob’s publickey from the directory and encrypts the message using it. Since only Bob has theprivate key only he can read the message (after decryption) and no one else. FurtherAruna can digitally sign the message. In this scheme anybody can verify that Arunadid indeed send the message and the message was not altered during transmission. ACertification Authority (CA)maintains the publicly available directory, which isresponsible for issuing and revoking digital certificates. A digital certificate containsthe public key of a user in the system. This framework is known as public keyinfrastructure (PKI).A user normally maintains his or her private key confidentially ina personal secure environment. SIM cards have the ability to store and process privatekeys. In terms of key management, there must be an administrative system to issuekey pairs to genuine citizens in a country.  Protocols A sample protocol that describes the transaction between a customer and amerchant, each using his or her mobile phone and a m-payment application serviceprovider as an intermediary (cf. generic architecture for m-payments in section 5above) is outlined in this section. It is assumed that customer and merchant areregistered as users with the m-payment application service provider (with theirrespective bank account details) and both of them have valid digital certificates. Thetransactions are detailed below. (i) Service Request Customer → Merchant 97

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING Customer makes a service request to the merchant (ii) Product Options Merchant → Customer: Merchant sends his product options and his certificate (iii)Product Selection Customer → Merchant: Customer selects a product; the selection is signed by the customer’s privatekey (iv)Payment Request Merchant →M-payment Application Solution Provider (MASP)→Customer:The payment request (containing the invoice amount) is signed using merchant’sprivate key. Customer can verify that the merchant is genuine by using hiscertificate(sent earlier in step 2). The MASP also authenticates the merchant beforepassing the payment request to the customer. (v) Payment Authorization Customer → MASP: The customer authorizes the payment request by digitally signing theauthorization using the customer’s private key. The MASP transfers the money fromthe buyer’s account to the seller’s account by communicating to the bank(s). (vi)Payment Confirmation MASP → Customer: MASP confirms payment made to merchant MASP→Merchant: MASP informs merchant of successful payment The customer and the merchant can verify their respective bank accounts as towhether payment has been made. The Institute for Development and Research in Banking Technology (IDRBT)has an experimental, proof–of-concept project where PKI enabled m-paymentapplications have been demonstrated to be feasible.7. Explain the Important features of iOS. A few important features of the iOS are the following:  Integrated search support enables simultaneous search through files, media, applications and email.  Gesture recognition supports, for example, shaking the device to undo the most recent action.  Google Maps direction services.  Push email.  Safari mobile browser.  Integrated camera and video.  Integrated media player.  Direct access to the Apple Store’s catalogue of applications, music, podcasts, television shows and movies. 98

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING  Compatibility with Apple’s cloud service, iCloud.8. Explain the features of android OS. A few important features of the android OS are the following:  Messaging  Web browser  Voice-based features  Multi-touch  Multitasking  Screen capture  Video calling  Multiple language support  Accessibility  Connectivity  Streaming media support  External storage 99

SEMESTER – VI COMPUTER SCIENCE AND ENGINEERING 100