Seize the Opportunity

Have you ever seen the movie â€Å"YES MAN† with Jim Carrey. I believe most of you do, which is one of my favorite movie. in this movie, Jim Carrey goes to this motivational seminar which teaches that you have to say ‘Yes’ to everything in life, and this will open unimaginable doors. So, Jim Carrey starts to say ‘Yes’ to everything and he starts to have all these amazing experiences and learns so many different . He got a promotion for his job, he find a girlfriend, and of course it’s a happy ending. Movies always come from reality, but it beyond reality.I think blindly saying yes to everything is not such a good idea, it will open opportunities and also might put you in trouble, so It’s easy to see many plots in this movie are not gonna happen in our life, but it still give us an important idea, which is having a positive attitude to every opportunity can bring success to you. We couldn’t live like a yes man say yes to everything , but we can use the following skills to seize the opportunity, which are say â€Å"yes† more often, have a positive attitude , take more risk. First of all, it’s impossible to say â€Å"Yes† to everything, but you could almost certainly say â€Å"Yes† to more than you do.When your friends invite you to join them to do something they like, and that you’ve never tried, what would you say. Do you take the chance to try it, or do you just put them down because you are too busy to do something else . If the first time human being saw the fire, and not try to make a fire, I guess we wouldn’t exist in this planet today. We all have potential, and potential is possibility. the only way to increase possibility is to learn more knowledge , to see more things, and to make more choices. So, let’s try it. Say â€Å"Yes† to something you would normally turn down.Try different food, try different music, have a conversation with different typ e of people. If you are shy, take guy way’s public speaking class. If you are noisy, try to be quiet and learn something from other. The world is huge, we should open ourselves to more opportunities, instead of staying where we are. Second, Positive attitude is very important to be successful and happy. Have you ever looked at people who always seem happy and enjoy life and wish you could be more like them? We are living in the same world, for some people, life is suffering, because they are easily broken down by any little trouble.For other people, life is paradise, because they have a positive attitude to face trouble. They always believe they are stronger than who they are, and they have more possibility to defeat any problem. According to Dr Becca Levy, a Harvard University social psychologist who focuses her research on aging and attitudes, a positive attitude will let you live longer. Therefore, never give up your belief. Whenever you give up , you close the door to suc cess. Being curious and happy, and with humor. Those positive attitudes will finally help you to seize the opportunity.Last, opportunities won’t last forever, and people always regret. According to wiki, the definition of opportunity is :a chance for advancement or profit and A favorable occasion or time. So, it takes risk and also short lived. When you’re sitting on couch watching TV, how much risk you are taking, and how many opportunities come to you? When a man start a new business, he is not only taking risk, but also taking advantage of an opportunity. Also, when you have your target, just do it and don’t hesitate, cause chance won't wait for you forever.For many examples, men want to chase a girl they like, they always want to set up a perfect time and encounter. However, when they finally get to the right time, someone else has already got there. Opportunity are not prepared for you, it’s for everyone. If you don’t take risk, you will regre t forever. In conclusion, in this huge planet, anything is possible. In order to follow your dream, you should size every chance. Saying â€Å"yes† is way to open more possibility, having a positive attitude will keep things going smoothly, and taking risk will lead you to success directly. When you have done those, opportunity is right in your hand.

Accounting Project Essay

Foundations of Accounting I Accounting Project Written by: Karen Pitsch Special thanks to Donna Larner Randiddle Co. is a merchandising business. Their account balances as of November 30, 2012 (unless otherwise indicated), are as follows: 110Cash$ 74,370 112Accounts Receivable 6,178 113Allowance for Doubtful Accounts 650 115Merchandise Inventory 2,346 116Prepaid Insurance 5,750 117Store Supplies 2,850 123Store Equipment 100,800 124Accumulated Depreciation-Store Equipment 31,060 210Accounts Payable 3,286 211Salaries Payable 0 218Interest Payable 0 220Note Payable (Due 2017) 30,000 ($6,000 to be paid in 2013) 310Randiddle, Capital (January 1, 2012) 46,288 311Randiddle, Withdrawals 60,000 312Income Summary 0 410Sales 296,130 411Sales Returns and Allowances 10,020 412Sales Discounts 7,200 510Cost of Goods Sold 30,250 520Sales Salaries Expense 34,400 521Advertising Expense 18,000 522Depreciation Expense 0 523Store Supplies Expense 0 529Miscellaneous Selling Expense 2,800 530Office Salaries Expense 25,500 531Rent Expense 24,200 532Insurance Expense 0 533Bad Debt Expense 0 539Miscellaneous Administrative Expense 1,650 550 Interest Expense 1,100 See more: Analysis of Starbucks coffee company employees essay Randiddle Co. uses the perpetual inventory system and the First-in, First-out costing method. Transportation-in and purchase discounts should be added to the Inventory Control Sheet, but since this will complicate the computation of the First-in, First-out costing method, please ignore this step in the process. They also use the Allowance Method for bad debt. The Accounts Receivable and Accounts Payable Subsidiary Ledgers along with the Inventory Control Sheet should be updated as each transaction affects them (daily). Randiddle Co. sells three types of microwave ovens. The sale prices of each are: 900 watt microwave: $199 1000 watt microwave: $299 1200 watt microwave: $499 During December, the last month of the accounting year, the following transactions were completed: Dec. 1. Issued check number 2632 for the December rent, $2,200. 2. Sold two 1200 watt microwaves for cash. 4. Purchased four 1000 watt microwaves on account from Matt Co., terms 2/10, n/30, FOB shipping point, $596. 5. Issued check number 2633 to pay the transportation charges on purchase of December 4, $89. (NOTE: Debit Merchandise Inventory. Do not include shipping and purchase discounts to the Inventory Control sheet for this project.) 6. Sold six 1000 watt microwaves and four 1200 watt microwaves on account to Briana Co., invoice 891, terms 2/10, n/30, FOB shipping point. 8. Issued check number 2634 for refund of cash on sales made for cash, $150. (Customer was going to return goods until an allowance was arranged.) 10. Purchased store supplies on account from Prince Co., terms n/30, $310. 10. Issued check to Matt Co. number 2635 for the full amount due, less discount allowed. (Round discount to nearest dollar.) 11. Paid Prince Co. full amount due, check number 2636. 12. Issued credit memo for one 1000 watt microwave returned on sale of December 6. (NOTE: Assume the returned microwave was from the 11/30 inventory) 13. Issued check number 2637 for advertising expense for last half of December, $3,000. 14. Received cash from Briana Co. for the full amount due (less return of December 12 and discount; round to nearest dollar). 19. Issued check number 2638 to buy five 900 watt microwaves, $495. 19. Issued check number 2639 for $596 to Joseph Co. on account. 20. Sold seven 900 watt microwaves on account to Cameron Co., invoice number 892, terms 1/10, n/30, FOB shipping point. 20. To expedite sale on Dec. 20, issued check number 2640 for shipping charges on sale to Cameron on December 20, $120 (NOTE: Cameron Co. will be reimbursing us for this shipping cost). 21. Received $1,396 cash from McKenzie Co. on account, no discount. 21. Purchased three 1200 watt microwaves on account from Elisha Co., terms 1/10, n/30, FOB shipping point, $747, shipping $78 (NOTE: Debit Merchandise Inventory $825, but only put $747 in the Inventory Control Sheet). 24. Received notification that Marie Co. has been granted bankruptcy with no amount of recovery. We are to write-off her amount due. (Note: See page 365 for entry required.) 26. Issued a debit memo for return of $249 because of damage to one 1200 watt microwave purchased on December 21, receiving credit from the seller. 27. Issued check number 2641 for sales salaries of $2,050 and office  salaries of $1,400. 28. Purchased store equipment on account from Joseph Co., terms n/30, FOB destination, $1,200. 29. Issued check number 2642 for store supplies, $70. 29. Purchased seven 1000 watt microwave from Prince Co, terms 1/10, n/30, FOB shipping point, for $1,113 on account, shipping $107. 30. Sold eight 1000 watt microwaves on account to Briana Co., invoice number 893, terms 2/10, n/30, FOB shipping point. 30. Received cash from sale of December 20, less discount, plus transportation paid on December 20. (Round calculations to the nearest dollar.) 31. Issued check number 2643 for purchase of December 21, less return of December 25 and discount. (Round discount to the nearest dollar.) 31. Issued a debit memo for $200 of the purchase returned from December 28. Instructions: 1. Enter the balances of each of the accounts in the appropriate balance column of the General Ledger (B-S and I-S Ledger). Write Balance in the item section, and place a (x) in the Post Reference column. 2. Journalize the transactions in a sales journal, purchases journal, cash receipts journal, cash payments journal, or general journal as illustrated in chapter 7. Also post to the Accounts Receivable and Accounts Payable Subsidiary ledgers and Inventory Control Sheet as needed. 3. Total each column on the special journals and prove the journals. 4. Post the totals of the account named columns and individually post the â€Å"Other Accounts† columns as well to the General Ledger. 5. Prepare the Schedule of Accounts Receivable and the Schedule of Accounts Payable (their total amount must equal the amount in their controlling general ledger account). 6. Prepare the unadjusted trial balance on the worksheet. 7. Complete the worksheet for the year ended December 31, 2012, using the following adjustment data: a. Merchandise inventory on December 31 $1,090 b. Insurance expired during the year 2,250 c. Store supplies on hand on December 31 850 d. Depreciation for the current year needs to be calculated. The business uses the Straight-line method, the store equipment has a useful life of 10 years with no salvage value. (NOTE: the purchase and return will not be included as the dates of the transactions were after the 15th of the month). e. Accrued salaries on December 31: Sales salaries$1,075 Office salaries 540 $1,615 f. The note payable terms are at 8%, payment is not being made until Jan. 3, 2013. Interest must be recognized for one month. g. Calculate the Bad Debt adjustment amount; net realizable value of Accounts Receivable is determined to be $6,313. 8. Prepare a multiple-step income statement, a statement of owner’s equity, and a classified balance sheet in good form. (Recommend review of â€Å"Current Liabilities† on page 149.) 9. Journalize and post the adjusting entries. 10. Journalize and post the closing entries. Indicate closed accounts by inserting a zero in both balance columns opposite the closing entry. 11. Prepare a post-closing trial balance.

Data and Computer Communications

DATA AND COMPUTER COMMUNICATIONS Eighth Edition William Stallings Upper Saddle River, New Jersey 07458 Library of Congress Cataloging-in-Publication Data on File Vice President and Editorial Director, ECS: Marcia J. Horton Executive Editor: Tracy Dunkelberger Assistant Editor: Carole Snyder Editorial Assistant: Christianna Lee Executive Managing Editor: Vince O’Brien Managing Editor: Camille Trentacoste Production Editor: Rose Kernan Director of Creative Services: Paul Belfanti Creative Director: Juan Lopez Cover Designer: Bruce Kenselaar Managing Editor,AV Management and Production: Patricia Burns  ©2007 Pearson Education, Inc.Pearson Prentice Hall Pearson Education, Inc. Upper Saddle River, NJ 07458 Art Editor: Gregory Dulles Director, Image Resource Center: Melinda Reo Manager, Rights and Permissions: Zina Arabia Manager,Visual Research: Beth Brenzel Manager, Cover Visual Research and Permissions: Karen Sanatar Manufacturing Manager, ESM: Alexis Heydt-Long Manufacturing B uyer: Lisa McDowell Executive Marketing Manager: Robin O’Brien Marketing Assistant: Mack Patterson All rights reserved. No part of this book may be reproduced in any form or by any means, without permission in writing from the publisher.Pearson Prentice Hallâ„ ¢ is a trademark of Pearson Education, Inc. All other tradmarks or product names are the property of their respective owners. The author and publisher of this book have used their best efforts in preparing this book. These efforts include the development, research, and testing of the theories and programs to determine their effectiveness. The author and publisher make no warranty of any kind, expressed or implied, with regard to these programs or the documentation contained in this book. The author and publisher shall not be liable in any event for incidental or consequential amages in connection with, or arising out of, the furnishing, performance, or use of these programs. Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 ISBN: 0-13-243310-9 Pearson Education Ltd. , London Pearson Education Australia Pty. Ltd. , Sydney Pearson Education Singapore, Pte. Ltd. Pearson Education North Asia Ltd. , Hong Kong Pearson Education Canada, Inc. , Toronto Pearson Educaci n de Mexico, S. A. de C. V. Pearson Education Japan, Tokyo Pearson Education Malaysia, Pte. Ltd. Pearson Education, Inc. , Upper Saddle River, New Jersey For my scintillating wife ATSWEB SITE FOR DATA AND COMPUTER COMMUNICATIONS, EIGHTH EDITION The Web site at WilliamStallings. com/DCC/DCC8e. html provides support for instructors and students using the book. It includes the following elements. Course Support Materials The course support materials include †¢ Copies of figures from the book in PDF format †¢ A detailed set of course notes in PDF format suitable for student handout or for use as viewgraphs †¢ A set of PowerPoint slides for use as lecture aids †¢ Computer Science Student Support Site: contains a number of links and documents that the student may find useful in his/her ongoing computer science education.The site includes a review of basic, relevant mathematics; advice on research, writing, and doing homework problems; links to computer science research resources, such as report repositories and bibliographies; and other useful links. †¢ An errata sheet for the book, updated at most monthly T DCC Courses The DCC8e Web site includes links to Web sites for courses taught using the book. These sites can provide useful ideas about scheduling and topic ordering, as well as a number of useful handouts and other materials. Useful Web Sites The DCC8e Web site includes links to relevant Web sites, organized by chapter.The links cover a broad spectrum of topics and will enable students to explore timely issues in greater depth. iv WEB SITE FOR DATA AND COMPUTER COMMUNICATIONS, EIGHTH EDITION v Supplemental Documents The DCC8e Web site includes a number of documents that expand on the treatment in the book. Topics include standards organizations, Sockets, TCP/IP checksum, ASCII, and the sampling theorem. Internet Mailing List An Internet mailing list is maintained so that instructors using this book can exchange information, suggestions, and questions with each other and the author.Subscription information is provided at the book’s Web site. Simulation and Modeling Tools The Web site includes links to the cnet Web site and the modeling tools Web site. These packages can be used to analyze and experiment with protocol and network design issues. Each site includes downloadable software and background information. The instructor’s manual includes more information on loading and using the software and suggested student projects. This page intentionally left blank CONTENTS Web Site for Data and Computer Communications Preface xv 1 iv Chapter 0 Reader’s and Instructor’s Guide 0. Outline of the Book 2 0. 2 Roadmap 3 0. 3 Internet and Web Resources 5 0. 4 Standards 6 PART ONE OVERVIEW 9 Chapter 1 Data Communications, Data Networking, and the Internet 10 1. 1 Data Communications and Networking for Today’s Enterprise 12 1. 2 A Communications Model 16 1. 3 Data Communications 19 1. 4 Networks 22 1. 5 The Internet 25 1. 6 An Example Configuration 29 Chapter 2 Protocol Architecture, TCP/IP, and Internet-Based Applications 2. 1 The Need for a Protocol Architecture 33 2. 2 The TCP/IP Protocol Architecture 34 2. 3 The OSI Model 42 2. 4 Standardization within a Protocol Architecture 44 2. Traditional Internet-Based Applications 48 2. 6 Multimedia 48 2. 7 Recommended Reading and Web Sites 53 2. 8 Key Terms, Review Questions, and Problems 54 Appendix 2A The Trivial File Transfer Protocol 57 PART TWO DATA COMMUNICATIONS 62 Chapter 3 Data Transmission 65 3. 1 Concepts and Terminology 67 3. 2 Analog and Digital Data Transmission 78 3. 3 Transmission Impairments 86 3. 4 Channel Capacity 91 3. 5 Recommended Reading and Web Si te 96 3. 6 Key Terms, Review Questions, and Problems Appendix 3A Decibels and Signal Strength 99 Chapter 4 Transmission Media 102 4. Guided Transmission Media 104 4. 2 Wireless Transmission 117 4. 3 Wireless Propagation 125 32 96 vii viii CONTENTS 4. 4 4. 5 4. 6 Line-of-Sight Transmission 129 Recommended Reading and Web Sites 133 Key Terms, Review Questions, and Problems 134 Chapter 5 Signal Encoding Techniques 138 5. 1 Digital Data, Digital Signals 141 5. 2 Digital Data, Analog Signals 151 5. 3 Analog Data, Digital Signals 162 5. 4 Analog Data, Analog Signals 168 5. 5 Recommended Reading 175 5. 6 Key Terms, Review Questions, and Problems 175 Chapter 6 Digital Data Communication Techniques 180 6. Asynchronous and Synchronous Transmission 182 6. 2 Types of Errors 186 6. 3 Error Detection 186 6. 4 Error Correction 196 6. 5 Line Configurations 201 6. 6 Recommended Reading 203 6. 7 Key Terms, Review Questions, and Problems 204 Chapter 7 Data Link Control Protocols 207 7. 1 Flow Control 209 7. 2 Error Control 216 7. 3 High-Level Data Link Control (HDLC) 222 7. 4 Recommended Reading 228 7. 5 Key Terms, Review Questions, and Problems 229 Appendix 7A Performance Issues 232 Chapter 8 Multiplexing 239 8. 1 Frequency-Division Multiplexing 242 8. 2 Synchronous Time-Division Multiplexing 248 8. Statistical Time-Division Multiplexing 258 8. 4 Asymmetric Digital Subscriber Line 265 8. 5 xDSL 268 8. 6 Recommended Reading and Web Sites 269 8. 7 Key Terms, Review Questions, and Problems 270 Chapter 9 Spread Spectrum 274 9. 1 The Concept of Spread Spectrum 276 9. 2 Frequency Hopping Spread Spectrum 277 9. 3 Direct Sequence Spread Spectrum 282 9. 4 Code-Division Multiple Access 287 9. 5 Recommended Reading and Web Site 290 9. 6 Key Terms, Review Questions, and Problems 291 CONTENTS ix PART THREE WIDE AREA NETWORKS 295 Chapter 10 Circuit Switching and Packet Switching 297 10. Switched Communications Networks 299 10. 2 Circuit Switching Networks 301 10. 3 Circuit Switching Concepts 304 10. 4 Softswitch Architecture 307 10. 5 Packet-Switching Principles 309 10. 6 X. 25 317 10. 7 Frame Relay 319 10. 8 Recommended Reading and Web Sites 324 10. 9 Key Terms, Review Questions, and Problems 325 Chapter 11 Asynchronous Transfer Mode 328 11. 1 Protocol Architecture 329 11. 2 ATM Logical Connections 331 11. 3 ATM Cells 335 11. 4 Transmission of ATM Cells 340 11. 5 ATM Service Categories 345 11. 6 Recommended Reading and Web Sites 348 11. Key Terms, Review Questions, and Problems 349 Chapter 12 Routing in Switched Networks 351 12. 1 Routing in Packet-Switching Networks 352 12. 2 Examples: Routing in ARPANET 362 12. 3 Least-Cost Algorithms 367 12. 4 Recommended Reading 372 12. 5 Key Terms, Review Questions, and Problems 373 Chapter 13 Congestion Control in Data Networks 377 13. 1 Effects of Congestion 379 13. 2 Congestion Control 383 13. 3 Traffic Management 386 13. 4 Congestion Control in Packet-Switching Networks 13. 5 Frame Relay Congestion Control 388 13. 6 ATM Traff ic Management 394 13. 7 ATM-GFR Traffic Management 406 13. Recommended Reading 409 13. 9 Key Terms, Review Questions, and Problems 410 Chapter 14 Cellular Wireless Networks 413 14. 1 Principles of Cellular Networks 415 14. 2 First Generation Analog 427 14. 3 Second Generation CDMA 429 14. 4 Third Generation Systems 437 14. 5 Recommended Reading and Web Sites 440 14. 6 Key Terms, Review Questions, and Problems 441 387 x CONTENTS PART FOUR LOCAL AREA NETWORKS 444 Chapter 15 Local Area Network Overview 446 15. 1 Background 448 15. 2 Topologies and Transmission Media 451 15. 3 LAN Protocol Architecture 457 15. 4 Bridges 465 15. 5 Layer 2 and Layer 3 Switches 473 15. Recommended Reading and Web Site 478 15. 7 Key Terms, Review Questions, and Problems 479 Chapter 16 High-Speed LANs 482 16. 1 The Emergence of High-Speed LANs 483 16. 2 Ethernet 485 16. 3 Fibre Channel 500 16. 4 Recommended Reading and Web Sites 504 16. 5 Key Terms, Review Questions, and Problems 506 Appendix 16A Digital Sig nal Encoding for LANs 508 Appendix 16B Performance Issues 514 Appendix 16C Scrambling 518 Chapter 17 Wireless LANs 522 17. 1 Overview 523 17. 2 Wireless LAN Technology 528 17. 3 IEEE 802. 11 Architecture and Services 531 17. 4 IEEE 802. 11 Medium Access Control 535 17. 5 IEEE 802. 1Physical Layer 543 17. 6 IEEE 802. 11 Security Considerations 549 Recommended Reading and Web Sites 550 17. 7 17. 8 Key Terms, Review Questions, and Problems 551 PART FIVE INTERNET AND TRANSPORT PROTOCOLS Chapter 18 Internetwork Protocols 556 18. 1 Basic Protocol Functions 558 18. 2 Principles of Internetworking 566 18. 3 Internet Protocol Operation 569 18. 4 Internet Protocol 576 18. 5 IPv6 586 18. 6 Virtual Private Networks and IP Security 596 18. 7 Recommended Reading and Web Sites 599 18. 8 Key Terms, Review Questions, and Problems 600 Chapter 19 Internetwork Operation 603 19. 1 Multicasting 605 19. Routing Protocols 614 19. 3 Integrated Services Architecture 625 19. 4 Differentiated Services 636 554 CONTENTS xi 19. 5 19. 6 19. 7 19. 8 Service Level Agreements 645 IP Performance Metrics 646 Recommended Reading and Web Sites 649 Key Terms, Review Questions, and Problems 651 657 Chapter 20 Transport Protocols 655 20. 1 Connection-Oriented Transport Protocol Mechanisms 20. 2 TCP 674 20. 3 TCP Congestion Control 683 20. 4 UDP 693 20. 5 Recommended Reading and Web Sites 695 Key Terms, Review Questions, and Problems 695 20. 6 PART SIX Chapter 21 21. 1 21. 2 21. 3 21. 4 21. 5 21. 6 21. 7 21. 8 21. INTERNET APPLICATIONS 699 Network Security 701 Security Requirements and Attacks 703 Confidentiality with Conventional Encryption 705 Message Authentication and Hash Functions 713 Public-Key Encryption and Digital Signatures 720 Secure Socket Layer and Transport Layer Security 727 IPv4 and IPv6 Security 732 Wi-Fi Protected Access 737 Recommended Reading and Web Sites 739 Key Terms, Review Questions, and Problems 740 Chapter 22 Internet Applications—Electronic Mail and Network Managemen t 22. 1 Electronic Mail: SMTP and MIME 745 22. 2 Network Management: SNMP 760 22. 3 Recommended Reading and Web Sites 770 22. Key Terms, Review Questions, and Problems 771 743 Chapter 23 Internet Applications—Internet Directory Service and World Wide Web 23. 1 Internet Directory Service: DNS 774 23. 2 Web Access: HTTP 784 23. 3 Recommended Reading and Web Sites 795 23. 4 Key Terms, Review Questions, and Problems 796 Chapter 24 Internet Applications—Multimedia 799 24. 1 Audio and Video Compression 800 24. 2 Real-Time Traffic 808 24. 3 Voice Over IP and Multimedia Support—SIP 811 24. 4 Real-Time Transport Protocol (RTP) 820 24. 5 Recommended Reading and Web Sites 831 24. 6 Key Terms, Review Questions, and Problems 832 773 ii CONTENTS APPENDICES 835 Appendix A Fourier Analysis 835 A. 1 Fourier Series Representation of Periodic Signals 836 A. 2 Fourier Transform Representation of Aperiodic Signals 837 A. 3 Recommended Reading 840 Appendix B Projects for Teaching Dat a and Computer Communications B. 1 Practical Exercises 842 B. 2 Sockets Projects 843 B. 3 Ethereal Projects 843 B. 4 Simulation and Modeling Projects 844 B. 5 Performance Modeling 844 B. 6 Research Projects 845 B. 7 Reading/Report Assignments 845 B. 8 Writing Assignments 845 B. 9 Discussion Topics 846 References Index 858 ONLINE APPENDICES WilliamStallings. om/DCC Appendix C Sockets: A Programmer’s Introduction C. 1 Versions of Sockets C. 2 Sockets, Socket Descriptors, Ports, and Connections The Client/Server Model of Communication C. 3 C. 4 Sockets Elements C. 5 Stream and Datagram Sockets C. 6 Run-Time Program Control C. 7 Remote Execution of a Windows Console Application Appendix D Standards Organizations D. 1 The Importance of Standards D. 2 Standards and Regulation D. 3 Standards-Setting Organizations Appendix E Appendix F The International Reference Alphabet Proof of the Sampling Theorem 847 841 Appendix G Physical-Layer Interfacing G. 1 V. 24/EIA-232-F G. ISDN Physical Interface Appendix H The OSI Model H. 1 The Model H. 2 The OSI Layers CONTENTS xiii Appendix I Queuing Effects I. 1 Queuing Models I. 2 Queuing Results Appendix J Orthogonality, Correlation, and Autocorrelation J. 1 Correlation and Autocorrelation J. 2 Orthogonal Codes Appendix K The TCP/IP Checksum K. 1 Ones-Complement Addition K. 2 Use in TCP and IP Appendix L TCP/IP Example Appendix M Uniform Resource Locators (URLs) and Uniform Resource Identifiers (URIs) M. 1 Uniform Resource Locator M. 2 Uniform Resource Identifier M. 3 To Learn More Appendix N Glossary Augmented Backus-Naur FormThis page intentionally left blank PREFACE Begin at the beginning and go on till you come to the end; then stop. —Alice in Wonderland, Lewis Carroll OBJECTIVES This book attempts to provide a unified overview of the broad field of data and computer communications. The organization of the book reflects an attempt to break this massive subject into comprehensible parts and to build, piece by piec e, a survey of the state of the art. The book emphasizes basic principles and topics of fundamental importance concerning the technology and architecture of this field and provides a detailed discussion of leading-edge topics.The following basic themes serve to unify the discussion: †¢ Principles: Although the scope of this book is broad, there are a number of basic principles that appear repeatedly as themes and that unify this field. Examples are multiplexing, flow control, and error control. The book highlights these principles and contrasts their application in specific areas of technology. †¢ Design approaches: The book examines alternative approaches to meeting specific communication requirements. †¢ Standards: Standards have come to assume an increasingly important, indeed dominant, role in this field.An understanding of the current status and future direction of technology requires a comprehensive discussion of the related standards. INTENDED AUDIENCE The book is intended for both an academic and a professional audience. For the professional interested in this field, the book serves as a basic reference volume and is suitable for self-study. As a textbook, it can be used for a one-semester or two-semester course. It covers the material in Networking (NET), a core area in the Information Technology body of knowledge, which is part of the Draft ACM/IEEE/AIS Computing Curricula 2005.The book also covers the material in Computer Networks (CE-NWK), a core area in Computer Engineering 2004 Curriculum Guidelines from the ACM/IEEE Joint Task Force on Computing Curricula. PLAN OF THE TEXT The book is divided into six parts (see Chapter 0): †¢ Overview †¢ Data Communications †¢ Wide Area Networks xv xvi PREFACE †¢ Local Area Networks †¢ Internet and Transport Protocols †¢ Internet Applications In addition, the book includes an extensive glossary, a list of frequently used acronyms, and a bibliography. Each chapter inc ludes problems and suggestions for further reading.The chapters and parts of the book are sufficiently modular to provide a great deal of flexibility in the design of courses. See Chapter 0 for a number of detailed suggestions for both top-down and bottom-up course strategies. INSTRUCTIONAL SUPPORT MATERIALS To support instructors, the following materials are provided: †¢ Solutions Manual: Solutions to all end-of-chapter Review Questions and Problems. †¢ PowerPoint Slides: A set of slides covering all chapters, suitable for use in lecturing. †¢ PDF files: Reproductions of all figures and tables from the book. Projects Manual: Suggested project assignments for all of the project categories listed below. Instructors may contact their Pearson Education or Prentice Hall representative for access to these materials. In addition, the book’s Web site supports instructors with: †¢ Links to Webs sites for other courses being taught using this book †¢ Sign up i nformation for an Internet mailing list for instructors INTERNET SERVICES FOR INSTRUCTORS AND STUDENTS There is a Web site for this book that provides support for students and instructors.The site includes links to other relevant sites, transparency masters of figures in the book, and sign-up information for the book’s Internet mailing list. The Web page is at WilliamStallings. com/DCC/DCC8e. html; see the section, Web Site for Data and Computer Communications, preceding the Table of Contents, for more information. An Internet mailing list has been set up so that instructors using this book can exchange information, suggestions, and questions with each other and with the author. As soon as typos or other errors are discovered, an errata list for this book will be available at WilliamStallings. om. PROJECTS AND OTHER STUDENT EXERCISES For many instructors, an important component of a data communications or networking course is a project or set of projects by which the student gets hands-on experience to reinforce concepts from the text. This book provides an unparalleled degree of support for including a projects component in the course. The instructor’s supplement not only includes guidance on how to assign and structure the projects but also includes a set of User’s PREFACE xvii Manuals for various project types plus specific assignments, all written especially for this book.Instructors can assign work in the following areas: †¢ Practical exercises: Using network commands, the student gains experience in network connectivity. †¢ Sockets programming projects: The book is supported by a detailed description of Sockets available at the book’s Web site. The Instructors supplement includes a set of programming projects. Sockets programming is an â€Å"easy† topic and one that can result in very satisfying hands-on projects for students. †¢ Ethereal projects: Ethereal is a protocol analyzer that enables students to study the behavior of protocols. Simulation projects: The student can use the simulation package cnet to analyze network behavior. †¢ Performance modeling projects: Two performance modeling techniques are provided a tools package and OPNET. †¢ Research projects: The instructor’s supplement includes a list of suggested research projects that would involve Web and literature searches. †¢ Reading/report assignments: The instructor’s supplement includes a list of papers that can be assigned for reading and writing a report, plus suggested assignment wording. Writing assignments: The instructor’s supplement includes a list of writing assignments to facilitate learning the material. †¢ Discussion topics: These topics can be used in a classroom, chat room, or message board environment to explore certain areas in greater depth and to foster student collaboration. This diverse set of projects and other student exercises enables the instructor to use t he book as one component in a rich and varied learning experience and to tailor a course plan to meet the specific needs of the instructor and students. See Appendix B for details.WHAT’S NEW IN THE EIGHTH EDITION This eighth edition is seeing the light of day less than four years after the publication of the seventh edition. During that time, the pace of change in this field continues unabated. In this new edition, I try to capture these changes while maintaining a broad and comprehensive coverage of the entire field. To begin the process of revision, the seventh edition of this book was extensively reviewed by a number of professors who teach the subject. The result is that, in many places, the narrative has been clarified and tightened, and illustrations have been improved.Also, a number of new â€Å"field-tested† problems have been added. Beyond these refinements to improve pedagogy and user friendliness, there have been major substantive changes throughout the book . Every chapter has been revised, new chapters have been added, and the overall organization of the book has changed. Highlights include: †¢ Updated coverage of Gigabit Ethernet and 10-Gbps Ethernet: New details of these standards are provided. †¢ Updated coverage of WiFi/IEEE 802. 11 wireless LANs: IEEE 802. 11 and the related WiFi specifications have continued to evolve. viii PREFACE †¢ New coverage of IP performance metrics and service level agreements (SLAs): These aspects of Quality of Service (QoS) and performance monitoring are increasingly important. †¢ Address Resolution Protocol (ARP): This important protocol is now covered. †¢ New coverage of TCP Tahoe, Reno, and NewReno: These congestion control algorithms are now common in most commercial implementations. †¢ Expanded coverage of security: Chapter 21 is more detailed; other chapters provide overview of security for the relevant topic.Among the new topics are Wi-Fi Protected Access (WPA) and the secure hash algorithm SHA-512. †¢ Domain Name System (DNS): This important scheme is now covered. †¢ New coverage of multimedia: Introductory section in Chapter 2; detailed coverage in Chapter 24. Topics covered include video compression, SIP, and RTP. †¢ Online appendices: Fourteen online appendices provide additional detail on important topics in the text, including Sockets programming, queuing models, the Internet checksum, a detailed example of TCP/IP operation, and the BNF grammar.In addition, throughout the book, virtually every topic has been updated to reflect the developments in standards and technology that have occurred since the publication of the seventh edition. ACKNOWLEDGMENTS This new edition has benefited from review by a number of people, who gave generously of their time and expertise. The following people reviewed all or a large part of the manuscript: Xin Liu- (UC, Davis), Jorge Cobb, Andras Farago, Dr. Prasant Mohapatra (UC Davis), Dr. Jingxi an Wu (Sonoma State University), G. R.Dattareya (UT Dallas), Guanling Chen (Umass, Lowell), Bob Roohaprvar (Cal State East Bay), Ahmed Banafa (Cal State East Bay), Ching-Chen Lee (CSU Hayward), and Daji Qaio (Iowa State). Thanks also to the many people who provided detailed technical reviews of a single chapter: Dave Tweed, Bruce Lane, Denis McMahon, Charles Freund, Paul Hoadley, Stephen Ma, Sandeep Subramaniam, Dragan Cvetkovic, Fernando Gont, Neil Giles, Rajesh Thundil, and Rick Jones. In addition, Larry Owens of California State University and Katia Obraczka of the University of Southern California provided some homework problems.Thanks also to the following contributors. Zornitza Prodanoff of the University of North Florida prepared the appendix on Sockets programming. Michael Harris of the University of South Florida is responsible for the Ethereal exercises and user’s guide. Lawrie Brown of the Australian Defence Force Academy of the University of New South Wales produc ed the PPT lecture slides. Finally, I would like to thank the many people responsible for the publication of the book, all of whom did their usual excellent job.This includes the staff at Prentice Hall, particularly my editor Tracy Dunkelberger, her assistants Christianna Lee and Carole Snyder, and production manager Rose Kernan. Also, Patricia M. Daly did the copy editing. CHAPTER READER’S AND INSTRUCTOR’S GUIDE 0. 1 0. 2 0. 3 0. 4 Outline of the Book Roadmap Internet and Web Resources Standards 0 1 2 CHAPTER 0 / READER’S AND INSTRUCTOR’S GUIDE â€Å"In the meanwhile, then,† demanded Li-loe, â€Å"relate to me the story to which reference has been made, thereby proving the truth of your assertion, and at the same time affording n entertainment of a somewhat exceptional kind. † â€Å"The shadows lengthen,† replied Kai Lung, â€Å"but as the narrative in question is of an inconspicuous span I will raise no barrier against your flatter ing request, especially as it indicates an awakening taste hitherto unexpected. † —Kai Lung’s Golden Hours, Earnest Bramah This book, with its accompanying Web site, covers a lot of material. Here we give the reader some basic background information. 0. 1 OUTLINE OF THE BOOK The book is organized into five parts: Part One. Overview: Provides an introduction to the range of topics covered in the book.This part includes a general overview of data communications and networking and a discussion of protocols, OSI, and the TCP/IP protocol suite. Part Two. Data Communications: Concerned primarily with the exchange of data between two directly connected devices. Within this restricted scope, the key aspects of transmission, interfacing, link control, and multiplexing are examined. Part Three. Wide Area Networks: Examines the internal mechanisms and user-network interfaces that have been developed to support voice, data, and multimedia communications over long-distance ne tworks.The traditional technologies of packet switching and circuit switching are examined, as well as the more recent ATM and wireless WANs. Separate chapters are devoted to routing and congestion control issues that are relevant both to switched data networks and to the Internet. Part Four. Local Area Networks: Explores the technologies and architectures that have been developed for networking over shorter distances. The transmission media, topologies, and medium access control protocols that are the key ingredients of a LAN design are explored and specific standardized LAN systems examined.Part Five. Networking Protocols: Explores both the architectural principles and the mechanisms required for the exchange of data among computers, workstations, servers, and other data processing devices. Much of the material in this part relates to the TCP/IP protocol suite. Part Six. Internet Applications: Looks at a range of applications that operate over the Internet. A more detailed, chapte r-by-chapter summary of each part appears at the beginning of that part. 0. 2 / ROADMAP 3 0. 2 ROADMAP Course EmphasisThe material in this book is organized into four broad categories: data transmission and communication; communications networks; network protocols; and applications and security. The chapters and parts of the book are sufficiently modular to provide a great deal of flexibility in the design of courses. The following are suggestions for three different course designs: †¢ Fundamentals of Data Communications: Parts One (overview) and Two (data communications) and Chapters 10 and 11 (circuit switching, packet switching, and ATM). Communications Networks: If the student has a basic background in data communications, then this course could cover Parts One (overview), Three (WAN), and Four (LAN). †¢ Computer Networks: If the student has a basic background in data communications, then this course could cover Part One (overview), Chapters 6 and 7 (data communication techniques and data link control), Part Five (protocols), and part or all of Part Six (applications). In addition, a more streamlined course that covers the entire book is possible by eliminating certain chapters that are not essential on a first reading.Chapters that could be optional are Chapters 3 (data transmission) and 4 (transmission media), if the student has a basic understanding of these topics; Chapter 8 (multiplexing); Chapter 9 (spread spectrum); Chapters 12 through 14 (routing, congestion control, cellular networks); Chapter 18 (internetworking); and Chapter 21 (network security). Bottom-Up versus Top-Down The book is organized in a modular fashion. After reading Part One, the other parts can be read in a number of possible sequences.Figure 0. 1a shows the bottom-up approach provided by reading the book from front to back. With this approach, each part builds on the material in the previous part, so that it is always clear how a given layer of functionality is supporte d from below. There is more material than can be comfortably covered in a single semester, but the book’s organization makes it easy to eliminate some chapters and maintain the bottom-up sequence. Figure 0. 1b suggests one approach to a survey course.Some readers, and some instructors, are more comfortable with a top-down approach. After the background material (Part One), the reader continues at the application level and works down through the protocol layers. This has the advantage of immediately focusing on the most visible part of the material, the applications, and then seeing, progressively, how each layer is supported by the next layer down. Figure 0. 1c is an example of a comprehensive treatment and Figure 0. 1d is an example of a survey treatment. 4 CHAPTER 0 / READER’S AND INSTRUCTOR’S GUIDEPart One Overview Part Two Data Communications Part Three Wide Area Networks Part Four Local Area Networks Part Five Internet and Transport Protocols Part Six Inter net Applications (a) A bottom-up approach Part One Overview Chapter 18 The Internet Protocol Part Six Internet Applications Part Five TCP/IP Part Three WANs Part Four LANs Part Two Data Communications (c) A top-down approach (d) Another top-down approach (b) Another bottom-up approach Part One Overview Chapter 18 The Internet Protocol Part Six Internet Applications Part Five TCP/IP Part Three WANs (10, 12) Part Four LANs (15) Part One Overview (1, 2) Part Two Data Communications (3, 6, 7, 8) Part Three WANs (10, 12) Part Four LANs (15) Part Five TCP/IP (18, 20) Figure 0. 1 Suggested Reading Orders Finally, it is possible to select chapters to reflect specific teaching objectives by not sticking to a strict chapter ordering. We give two examples used in courses taught with the seventh edition.One course used the sequence Part One (Overview); Chapter 3 (Data Transmission); Chapter 6 (Digital Data Communications Techniques); Chapter 7 (Data Link Control); Chapter 15 (LAN Overview); Cha pter 16 (High-Speed LANs); Chapter 10 (Circuit and Packet Switching); Chapter 12 (Routing); Chapter 18 (Internet Protocols); and Chapter 19 (Internet Operation). The other course used the sequence Part One (Overview); Chapter 3 (Data Transmission); Chapter 4 (Guided and Wireless Transmission); Chapter 5 (Signal Encoding Techniques); Chapter 8 (Multiplexing); Chapter 15 (LAN 0. 3 / INTERNET AND WEB RESOURCES 5 Overview); Chapter 16 (High-Speed LANs); Chapter 10 (Circuit and Packet Switching); Chapter 20 (Transport Protocols); Chapter 18 (Internet Protocols); and Chapter 19 (Internet Operation). 0. 3 INTERNET AND WEB RESOURCES There are a number of resources available on the Internet and the Web to support this book and to help one keep up with developments in this field.Web Sites for This Book A special Web page has been set up for this book at WilliamStallings. com/DCC/ DCC8e. html. See the two-page layout at the beginning of this book for a detailed description of that site. As soo n as any typos or other errors are discovered, an errata list for this book will be available at the Web site. Please report any errors that you spot. Errata sheets for my other books are at WilliamStallings. com. I also maintain the Computer Science Student Resource Site, at WilliamStallings. com/StudentSupport. html. The purpose of this site is to provide documents, information, and links for computer science students and professionals.Links and documents are organized into four categories: †¢ Math: Includes a basic math refresher, a queuing analysis primer, a number system primer, and links to numerous math sites †¢ How-to: Advice and guidance for solving homework problems, writing technical reports, and preparing technical presentations †¢ Research resources: Links to important collections of papers, technical reports, and bibliographies †¢ Miscellaneous: A variety of useful documents and links Other Web Sites There are numerous Web sites that provide informa tion related to the topics of this book. In subsequent chapters, pointers to specific Web sites can be found in the Recommended Reading and Web Sites section. Because the addresses for Web sites tend to change frequently, I have not included URLs in the book. For all of the Web sites listed in the book, the appropriate link can be found at this book’s Web site. Other links not mentioned in this book will be added to the Web site over time.The following are Web sites of general interest related to data and computer communications: †¢ Network World: Information and links to resources about data communications and networking. †¢ IETF: Maintains archives that relate to the Internet and IETF activities. Includes keyword-indexed library of RFCs and draft documents as well as many other documents related to the Internet and related protocols. 6 CHAPTER 0 / READER’S AND INSTRUCTOR’S GUIDE †¢ Vendors: Links to thousands of hardware and software vendors who currently have Web sites, as well as a list of thousands of computer and networking companies in a phone directory. †¢ IEEE Communications Society: Good way to keep up on conferences, publications, and so on. ACM Special Interest Group on Communications (SIGCOMM): Good way to keep up on conferences, publications, and so on. †¢ International Telecommunications Union: Contains a listing of ITU-T recommendations, plus information on obtaining ITU-T documents in hard copy or on DVD. †¢ International Organization for Standardization: Contains a listing of ISO standards, plus information on obtaining ISO documents in hard copy or on CD-ROM. †¢ CommWeb: Links to vendors, tutorials, and other useful information. †¢ CommsDesign: Lot of useful articles, tutorials, and product information. A bit hard to navigate, but worthwhile. USENET Newsgroups A number of USENET newsgroups are devoted to some aspect of data communications, networks, and protocols.As with virtually all USENET groups, there is a high noise-to-signal ratio, but it is worth experimenting to see if any meet your needs. The most relevant are as follows: †¢ comp. dcom. lans, comp. dcom. lans. misc: General discussions of LANs †¢ comp. dcom. lans. ethernet: Covers Ethernet, Ethernet-like systems, and the IEEE 802. 3 CSMA/CD standards †¢ comp. std. wireless: General discussion of wireless networks, including wireless LANs †¢ comp. security. misc: Computer security and encryption †¢ comp. dcom. cell-relay: Covers ATM and ATM LANs †¢ comp. dcom. frame-relay: Covers frame relay networks †¢ comp. dcom. net-management: Discussion of network management applications, protocols, and standards †¢ comp. rotocols. tcp-ip: The TCP/IP protocol suite 0. 4 STANDARDS It has long been accepted in the telecommunications industry that standards are required to govern the physical, electrical, and procedural characteristics of communication equipment. In the past, this view has not been embraced by the computer industry. Whereas communication equipment vendors recognize that their 0. 4 / STANDARDS 7 equipment will generally interface to and communicate with other vendors’ equipment, computer vendors have traditionally attempted to monopolize their customers. The proliferation of computers and distributed processing has made that an untenable position.Computers from different vendors must communicate with each other and, with the ongoing evolution of protocol standards, customers will no longer accept special-purpose protocol conversion software development. The result is that standards now permeate all of the areas of technology discussed in this book. There are a number of advantages and disadvantages to the standards-making process. We list here the most striking ones. The principal advantages of standards are as follows: †¢ A standard assures that there will be a large market for a particular piece of equipment or software. Thi s encourages mass production and, in some cases, the use of large-scale-integration (LSI) or very-large-scale-integration (VLSI) techniques, resulting in lower costs. A standard allows products from multiple vendors to communicate, giving the purchaser more flexibility in equipment selection and use. The principal disadvantages are as follows: †¢ A standard tends to freeze the technology. By the time a standard is developed, subjected to review and compromise, and promulgated, more efficient techniques are possible. †¢ There are multiple standards for the same thing. This is not a disadvantage of standards per se, but of the current way things are done. Fortunately, in recent years the various standards-making organizations have begun to cooperate more closely. Nevertheless, there are still areas where multiple conflicting standards exist.Throughout this book, we describe the most important standards in use or being developed for various aspects of data and computer commun ications. Various organizations have been involved in the development or promotion of these standards. The following are the most important (in the current context) of these organizations: †¢ Internet Society: The Internet SOCiety (ISOC) is a professional membership society with more than 150 organizational and 6000 individual members in over 100 countries. It provides leadership in addressing issues that confront the future of the Internet and is the organization home for the groups responsible for Internet infrastructure standards, including the Internet Engineering Task Force (IETF) and the Internet Architecture Board (IAB).All of the RFCs and Internet standards are developed through these organizations. †¢ IEEE 802: The IEEE (Institute of Electrical and Electronics Engineers) 802 LAN/MAN Standards Committee develops local area network standards and metropolitan area network standards. The most widely used standards are for the Ethernet family, wireless LAN, bridging, a nd virtual bridged LANs. An individual working group provides the focus for each area. 8 CHAPTER 0 / READER’S AND INSTRUCTOR’S GUIDE †¢ ITU-T: The International Telecommunication Union (ITU) is an international organization within the United Nations System where governments and the private sector coordinate global telecom networks and services.The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors of the ITU. ITU-T’s mission is the production of standards covering all fields of telecommunications. †¢ ATM Forum: The ATM Forum is an international nonprofit organization formed with the objective of accelerating the use of ATM (asynchronous transfer mode) products and services through a rapid convergence of interoperability specifications. In addition, the Forum promotes industry cooperation and awareness. †¢ ISO: The International Organization for Standardization (ISO)1 is a worldwide federation of national standards bod ies from more than 140 countries, one from each country.ISO is a nongovernmental organization that promotes the development of standardization and related activities with a view to facilitating the international exchange of goods and services, and to developing cooperation in the spheres of intellectual, scientific, technological, and economic activity. ISO’s work results in international agreements that are published as International Standards. A more detailed discussion of these organizations is contained in Appendix D. 1 ISO is not an acronym (in which case it would be IOS), but a word, derived from the Greek, meaning equal. PART ONE Overview The purpose of Part One is to provide a background and context for the remainder of this book. The broad range of topics that are encompassed in the field of data and computer communications is introduced, and the fundamental concepts of protocols and protocol architectures are examined.ROAD MAP FOR PART ONE Chapter 1 Data Communicati ons, Data Networks, and The Internet Chapter 1 provides an overview of Parts Two through Four of the book, giving the â€Å"big picture. † In essence, the book deals with four topics: data communications over a transmission link; wide area networks; local area networks; and protocols and the TCP/IP protocol architecture. Chapter 1 provides a preview of the first three of these topics. Chapter 2 Protocol Architecture, TCP/IP, and Internet-Based Applications Chapter 2 discusses the concept protocol architectures. This chapter can be read immediately following Chapter 1 or deferred until the beginning of Part Three, Four, or Five.After a general introduction, the chapter deals with the two most important protocol architectures: the Open Systems Interconnection (OSI) model and TCP/IP. Although the OSI model is often used as the framework for discourse in this area, it is the TCP/IP protocol suite that is the basis for most commercially available interoperable products and that is the focus of Parts Five and Six of this book. 9 CHAPTER DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 Data Communications and Networking for Today’s Enterprise A Communications Model Data Communications Networks The Internet An Example Configuration 1 10 The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point. The Mathematical Theory of Communication, Claude Shannon KEY POINTS †¢ The scope of this book is broad, covering three general areas: data communications, networking, and protocols; the first two are introduced in this chapter. Data communications deals with the transmission of signals in a reliable and efficient manner. Topics covered include signal transmission, transmission media, signal encoding, interfacing, data link control, and multiplexing. Networking deals with the technology and architecture of the communications networks used to interconnect communicating devices. This field is generally divided into the topics of local area networks (LANs) and wide area networks (WANs). †¢ †¢The 1970s and 1980s saw a merger of the fields of computer science and data communications that profoundly changed the technology, products, and companies of the now combined computer-communications industry. The computercommunications revolution has produced several remarkable facts: †¢ There is no fundamental difference between data processing (computers) and data communications (transmission and switching equipment). †¢ There are no fundamental differences among data, voice, and video communications. †¢ The distinction among single-processor computer, multiprocessor computer, local network, metropolitan network, and long-haul network has blurred.One effect of these trends has been a growing overlap of the computer and communications industries, from component fabrication to system integration. Another resul t is the development of integrated systems that transmit and process all types of data and information. Both the technology and the technical standards organizations are driving toward integrated public systems that make virtually all data and information sources around the world easily and uniformly accessible. This book aims to provide a unified view of the broad field of data and computer communications. The organization of the book reflects an attempt to break this massive subject into comprehensible parts and to build, piece by piece, a survey of the state of the art.This introductory chapter begins with a general model of communications. Then a brief discussion introduces each of the Parts Two through Four of this book. Chapter 2 provides an overview to Parts Five and Six 11 12 CHAPTER 1 / DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET 1. 1 DATA COMMUNICATIONS AND NETWORKING FOR TODAY’S ENTERPRISE Effective and efficient data communication and networking facilitie s are vital to any enterprise. In this section, we first look at trends that are increasing the challenge for the business manager in planning and managing such facilities. Then we look specifically at the requirement for ever-greater transmission speeds and network capacity. TrendsThree different forces have consistently driven the architecture and evolution of data communications and networking facilities: traffic growth, development of new services, and advances in technology. Communication traffic, both local (within a building or building complex) and long distance, both voice and data, has been growing at a high and steady rate for decades. The increasing emphasis on office automation, remote access, online transactions, and other productivity measures means that this trend is likely to continue. Thus, managers are constantly struggling to maximize capacity and minimize transmission costs. As businesses rely more and more on information technology, the range of services expand s. This increases the demand for high-capacity networking and transmission facilities.In turn, the continuing growth in high-speed network offerings with the continuing drop in prices encourages the expansion of services. Thus, growth in services and growth in traffic capacity go hand in hand. Figure 1. 1 gives some examples of information-based services and the data rates needed to support them [ELSA02]. Finally, trends in technology enable the provision of increasing traffic capacity and the support of a wide range of services. Four technology trends are particularly notable: 1. The trend toward faster and cheaper, both in computing and communications, continues. In terms of computing, this means more powerful computers and clusters of computers capable of supporting more demanding applications, such as multimedia applications.In terms of communications, the increasing use of optical fiber has brought transmission prices down and greatly increased capacity. For example, for long-d istance telecommunication and data network links, recent offerings of dense wavelength division multiplexing (DWDM) enable capacities of many terabits per second. For local area networks (LANs) many enterprises now have Gigabit Ethernet backbone networks and some are beginning to deploy 10-Gbps Ethernet. 2. Both voice-oriented telecommunications networks, such as the public switched telephone network (PSTN), and data networks, including the Internet, are more â€Å"intelligent† than ever. Two areas of intelligence are noteworthy.First, today’s networks can offer differing levels of quality of service (QoS), which include specifications for maximum delay, minimum throughput, and so on. Second, today’s networks provide a variety of customizable services in the areas of network management and security. 1. 1 / DATA COMMUNICATIONS AND NETWORKING FOR TODAY’S ENTERPRISE Speed (kbps) Transaction processing Messaging/text apps Voice Location services Still image t ransfers Internet/VPN access Database access Enhanced Web surfing Low-quality video Hifi audio Large file transfer Moderate video Interactive entertainment High-quality video Performance: Poor Adequate Good 9. 6 14. 4 28 64 144 384 2000 13 VPN: virtual private network Figure 1. 1 Services versus Throughput Rates 3.The Internet, the Web, and associated applications have emerged as dominant features of both the business and personal world, opening up many opportunities and challenges for managers. In addition to exploiting the Internet and the Web to reach customers, suppliers, and partners, enterprises have formed intranets and extranets1 to isolate their proprietary information free from unwanted access. 4. There has been a trend toward ever-increasing mobility for decades, liberating workers from the confines of the physical enterprise. Innovations include voice mail, remote data access, pagers, fax, e-mail, cordless phones, cell phones and cellular networks, and Internet portals.T he result is the ability of employees to take their business context with them as they move about. We are now seeing the growth of high-speed wireless access, which further enhances the ability to use enterprise information resources and services anywhere. 1 Briefly, an intranet uses Internet and Web technology in an isolated facility internal to an enterprise; an extranet extends a company’s intranet out onto the Internet to allow selected customers, suppliers, and mobile workers to access the company’s private data and applications. 14 CHAPTER 1 / DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET Data Transmission and Network Capacity RequirementsMomentous changes in the way organizations do business and process information have been driven by changes in networking technology and at the same time have driven those changes. It is hard to separate chicken and egg in this field. Similarly, the use of the Internet by both businesses and individuals reflects this cycli c dependency: the availability of new image-based services on the Internet (i. e. , the Web) has resulted in an increase in the total number of users and the traffic volume generated by each user. This, in turn, has resulted in a need to increase the speed and efficiency of the Internet. On the other hand, it is only such increased speed that makes the use of Web-based applications palatable to the end user.In this section, we survey some of the end-user factors that fit into this equation. We begin with the need for high-speed LANs in the business environment, because this need has appeared first and has forced the pace of networking development. Then we look at business WAN requirements. Finally we offer a few words about the effect of changes in commercial electronics on network requirements. The Emergence of High-Speed LANs Personal computers and microcomputer workstations began to achieve widespread acceptance in business computing in the early 1980s and have now achieved virtu ally the status of the telephone: an essential tool for office workers.Until relatively recently, office LANs provided basic connectivity services—connecting personal computers and terminals to mainframes and midrange systems that ran corporate applications, and providing workgroup connectivity at the departmental or divisional level. In both cases, traffic patterns were relatively light, with an emphasis on file transfer and electronic mail. The LANs that were available for this type of workload, primarily Ethernet and token ring, are well suited to this environment. In the 1990s, two significant trends altered the role of the personal computer and therefore the requirements on the LAN: 1. The speed and computing power of personal computers continued to enjoy explosive growth. These more powerful platforms support graphics-intensive applications and ever more elaborate graphical user interfaces to the operating system. . MIS (management information systems) organizations hav e recognized the LAN as a viable and essential computing platform, resulting in the focus on network computing. This trend began with client/server computing, which has become a dominant architecture in the business environment and the more recent Webfocused intranet trend. Both of these approaches involve the frequent transfer of potentially large volumes of data in a transaction-oriented environment. The effect of these trends has been to increase the volume of data to be handled over LANs and, because applications are more interactive, to reduce the acceptable delay on data transfers.The earlier generation of 10-Mbps Ethernets and 16-Mbps token rings was simply not up to the job of supporting these requirements. The following are examples of requirements that call for higher-speed LANs: †¢ Centralized server farms: In many applications, there is a need for user, or client, systems to be able to draw huge amounts of data from multiple centralized servers, called server farms. An example is a color publishing operation, in 1. 1 / DATA COMMUNICATIONS AND NETWORKING FOR TODAY’S ENTERPRISE 15 which servers typically contain tens of gigabytes of image data that must be downloaded to imaging workstations. As the performance of the servers themselves has increased, the bottleneck has shifted to the network. Power workgroups: These groups typically consist of a small number of cooperating users who need to draw massive data files across the network. Examples are a software development group that runs tests on a new software version, or a computer-aided design (CAD) company that regularly runs simulations of new designs. In such cases, large amounts of data are distributed to several workstations, processed, and updated at very high speed for multiple iterations. †¢ High-speed local backbone: As processing demand grows, LANs proliferate at a site, and high-speed interconnection is necessary. Corporate Wide Area Networking Needs As recently as the ear ly 1990s, there was an emphasis in many organizations on a centralized data processing model.In a typical environment, there might be significant computing facilities at a few regional offices, consisting of mainframes or well-equipped midrange systems. These centralized facilities could handle most corporate applications, including basic finance, accounting, and personnel programs, as well as many of the business-specific applications. Smaller, outlying offices (e. g. , a bank branch) could be equipped with terminals or basic personal computers linked to one of the regional centers in a transaction-oriented environment. This model began to change in the early 1990s, and the change accelerated through the mid-1990s. Many organizations have dispersed their employees into multiple smaller offices.There is a growing use of telecommuting. Most significant, the nature of the application structure has changed. First client/server computing and, more recently, intranet computing have funda mentally restructured the organizational data processing environment. There is now much more reliance on personal computers, workstations, and servers and much less use of centralized mainframe and midrange systems. Furthermore, the virtually universal deployment of graphical user interfaces to the desktop enables the end user to exploit graphic applications, multimedia, and other data-intensive applications. In addition, most organizations require access to the Internet.When a few clicks of the mouse can trigger huge volumes of data, traffic patterns have become more unpredictable while the average load has risen. All of these trends means that more data must be transported off premises and into the wide area. It has long been accepted that in the typical business environment, about 80% of the traffic remains local and about 20% traverses wide area links. But this rule no longer applies to most companies, with a greater percentage of the traffic going into the WAN environment [COHE 96]. This traffic flow shift places a greater burden on LAN backbones and, of course, on the WAN facilities used by a corporation.Thus, just as in the local area, changes in corporate data traffic patterns are driving the creation of high-speed WANs. Digital Electronics The rapid conversion of consumer electronics to digital technology is having an impact on both the Internet and corporate intranets. As these new gadgets come into view and proliferate, they dramatically increase the amount of image and video traffic carried by networks. Two noteworthy examples of this trend are digital versatile disks (DVDs) and digital still cameras. With the capacious DVD, the electronics industry has at last 16 CHAPTER 1 / DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET found an acceptable replacement for the analog VHS videotape.The DVD has replaced the videotape used in videocassette recorders (VCRs) and replaced the CD-ROM in personal computers and servers. The DVD takes video into the di gital age. It delivers movies with picture quality that outshines laser disks, and it can be randomly accessed like audio CDs, which DVD machines can also play. Vast volumes of data can be crammed onto the disk, currently seven times as much as a CDROM. With DVD’s huge storage capacity and vivid quality, PC games have become more realistic and educational software incorporates more video. Following in the wake of these developments is a new crest of traffic over the Internet and corporate intranets, as this material is incorporated into Web sites. A related product development is the digital camcorder.This product has made it easier for individuals and companies to make digital video files to be placed on corporate and Internet Web sites, again adding to the traffic burden. 1. 2 A COMMUNICATIONS MODEL This section introduces a simple model of communications, illustrated by the block diagram in Figure 1. 2a. The fundamental purpose of a communications system is the exchange of data between two parties. Figure 1. 2b presents one particular example, which is communication between a workstation and a server over a public telephone network. Another example is the exchange of voice signals between two telephones over the same network. The key elements of the model are as follows: †¢ Source.This device generates the data to be transmitted; examples are telephones and personal computers. Source system Destination system Source Transmitter Transmission System (a) General block diagram Receiver Destination Workstation Modem Public telephone network (b) Example Modem Server Figure 1. 2 Simplified Communications Model 1. 2 / A COMMUNICATIONS MODEL 17 †¢ Transmitter: Usually, the data generated by a source system are not transmitted directly in the form in which they were generated. Rather, a transmitter transforms and encodes the information in such a way as to produce electromagnetic signals that can be transmitted across some sort of transmission system .For example, a modem takes a digital bit stream from an attached device such as a personal computer and transforms that bit stream into an analog signal that can be handled by the telephone network. †¢ Transmission system: This can be a single transmission line or a complex network connecting source and destination. †¢ Receiver: The receiver accepts the signal from the transmission system and converts it into a form that can be handled by the destination device. For example, a modem will accept an analog signal coming from a network or transmission line and convert it into a digital bit stream. †¢ Destination: Takes the incoming data from the receiver.This simple narrative conceals a wealth of technical complexity. To get some idea of the scope of this complexity, Table 1. 1 lists some of the key tasks that must be performed in a data communications system. The list is somewhat arbitrary: Elements could be added; items on the list could be merged; and some items repr esent several tasks that are performed at different â€Å"levels† of the system. However, the list as it stands is suggestive of the scope of this book. The first item, transmission system utilization, refers to the need to make efficient use of transmission facilities that are typically shared among a number of communicating devices.Various techniques (referred to as multiplexing) are used to allocate the total capacity of a transmission medium among a number of users. Congestion control techniques may be required to assure that the system is not overwhelmed by excessive demand for transmission services. To communicate, a device must interface with the transmission system. All the forms of communication discussed in this book depend on the use of electromagnetic signals propagated over a transmission medium. Thus, once an interface is established, signal generation is required for communication. The properties of the signal, such as form and intensity, must be such that the signal is (1) capable of being propagated through the transmission system, and (2) interpretable as data at the receiver.Not only must the signals be generated to conform to the requirements of the transmission system and receiver, but also there must be some form of synchronization Table 1. 1 Communications Tasks Transmission system utilization Interfacing Signal generation Synchronization Exchange management Error detection and correction Flow control Addressing Routing Recovery Message formatting Security Network management 18 CHAPTER 1 / DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET between transmitter and receiver. The receiver must be able to determine when a signal begins to arrive and when it ends. It must also know the duration of each signal element.Beyond the basic matter of deciding on the nature and timing of signals, there is a variety of requirements for communication between two parties that might be collected under the term exchange management. If data are to be exchanged in both directions over a period of time, the two parties must cooperate. For example, for two parties to engage in a telephone conversation, one party must dial the number of the other, causing signals to be generated that result in the ringing of the called phone. The called party completes a connection by lifting the receiver. For data processing devices, more will be needed than simply establishing a connection; certain conventions must be decided on.These conventions may include whether both devices may transmit simultaneously or must take turns, the amount of data to be sent at one time, the format of the data, and what to do if certain contingencies such as an error arise. The next two items might have been included under exchange managem

BRAPS Coursework Example | Topics and Well Written Essays - 1250 words

BRAPS - Coursework Example It is focusing on developing branches in rural areas as well (Barclays.com- About Us, 2011). The main products offered by the company include commercial banking, retail banking, private equity, investment management, and investment banking. They have also introduced the latest service of trading iShares (Barclays.com- Products and Services, 2011). Barclays is managed by Marcus Agius, the team director who joined the company’s board in 2006 replacing Mathew Barrett as chairperson in 2007 (Barclays.com- About Us, 2011). The Barclays Vision is dedicated to being the international premier financial and banking services. They focus on obtaining superior financial and functional outcomes while keeping the international business standard. These unchanging anticipations offer the basis for our dedication to those with whom we associate. Barclays’ mission statement is to be creative, client-based Group, which delivers excellent products and services, make sure superb careers for our people, and participate actively to the society in which we work and live (Barclays.com- Executing our Strategy, 2011). Barclays bank has more than 2000 UK high street branches along with the Woolwich branches. Internationally, Barclays has more than 5200 branches with most 24/7 cash machine that can be used by Barclays clients as well as other customers at a fee. There are around 150,000 employees working at Barclays throughout the world. Barclays has an international market share as well as the local market share. This is an international corporation and, therefore, it operates worldwide. The financial data for the year 2010 is that the company boosted of 31.440 billion pounds, while their operating income was 6.065 billion pounds (Barclays.com – Annual report, 2011). The top competitors of Barclay bank include American Express Company, Capital One Financial Corporation, and Alliances Data Systems Corporation.

A case study report- POLYSUBSTANCE ABUSE Term Paper

A case study report- POLYSUBSTANCE ABUSE - Term Paper Example Furthermore, although it is not known which factors actually contribute to the polysubstance abuse, perhaps, a mix of many factors actually precipitates it. Chaotic home environment, parental substance abuse, parental mental illness, ineffective parenting, and lack of parental involvement, all of which seem to arise from a family environment are factors that need to be considered in this case. It is considered that family factors are most crucial in promoting drug abuse by the youth. Even the mentally healthy youth demonstrates high risk of abusing when the parents abuse. Poor parental attachment, nurturing, and monitoring, increase the risks of developing substance abuse. It is evident from Antonios case that he was in the middle of a dysfunctional family life. His fathers alcohol abuse and constant domestic fight between his parents leading to marital disruption can be functionally responsible for Antonios abuse behaviors. These led to substantial amount of stress at home and is definitely causative of little or no cohesion, organization, expressiveness, consistency, all leading to absence of communication between family members. More over, in Antonios case, there had been marital disruption between his parents over alcohol abuse, and this could have led to the belief that substance abuse is a normal part of the life. Cohesion among family members prevents delinquency, depression and low self-esteem and fosters self-control and absence of all of these increases the level of social estrangement that strongly predisposes to substance abuse (Dinges & Oetting, 1993). Sudden change in environment occurred in Antonios life due to their relocation from Huntington Beach to Redlands. It created pressure on him, and the factor of ineffective coping came into play. This led to his association with conduct-disordered peers, which was another precipitating factor. Lack of

Psychology of Performance research about my next project Term Paper

Psychology of Performance research about my next project - Term Paper Example After long wanderings Charles returns to the coop just to learn painful truth- dead chickens were infected with bird flu and were killed by the elder and the cow to prevent contamination. Emma knew everything and also wanted to save the lives in the coop. Charles becomes involved into a process of birds â€Å"saving† by killing those which caught the flu but fails to kill his friend Marcy. Finally all chickens and hens die because of the virus and Charles finds out that he has become a main killer himself. The genre can be characterized as adult animation because the scenario is written mostly for the audience older than at least 16-18 year olds. The animation is surreal and mock with main heroes acting like people in the similar to criminal world situations. Obviously, the film incorporates a big quantity of violence and has a plot that is a bit difficult to follow for younger audience. Some details are intentionally shown with attention to injuries and aggression. The film, however, has adult sarcasm which can be understood by the auditory with good sense of humor. The animation also explores some adult social and philosophical issues with major hero dealing with the difficult choice. The audience might mostly consist of men probably because the animation does not have many female characters and any typical attractions for women such as romantic story. The only â€Å"woman† in a film also does not have a good reputation which shows that the world described is a â€Å"men`s world†. However, Emma, the only hen, is shown as brave, loyal, and decisive who can be appreciated by more women nowadays. As the animation is full of scenes of aggression and risky behaviors the film must evoke anxiety in audience first of all. However, taking into account that it is still looks a bit ironical to observe hens and chickens acting like criminals, this emotion can be mixed with amusement and irony. In some cases the

International Finance Paper (Home Depot) Essay Example | Topics and Well Written Essays - 1500 words

International Finance Paper (Home Depot) - Essay Example During the years 2008 and 2009, the company was forced to lay off more than a thousand employees and 54 stores across US had to be closed. This includes the whole of the EXPO Design Centre Chain, which was engaged in high end retailing. In the year 2009 the company logged a sales figure of $71.288 billion, which was $20 billion less than was at it was in 2007. This paper deals with the various financial issues encountered by Home Depot during the course of its operation and talks about the measures, which the company is undertaking to deal with the same. As a business policy, HDI was engaged in mergers and acquisitions from the early days of its operations. The company also later on diversified its operation into other countries like Canada and Mexico, where in it needed expert advice on the various complex issues related to international finance. In these circumstances the company made a deal with Invemed Associates, who are engaged in the business of investment banking. An investment bank has departments like the Corporate Finance, which deals in the areas of mergers and acquisitions along with providing finance related consultancy to the clients. Another important division in the company is of the Research, which is concerned with analysis and valuation of shares and bonds, the recommendations on which are then presented to the clients. An investment bank also provides consultancy to their client’s for raising debts and equity from the market. Invemed Associates is required to constantly monitor the financial health of HDI and report on the same to the Board of Directors of HDI. Invemed is also required to inform the board on any economic trend that is relevant to the type of business in which the company is engaged in. Invemed Associates advises HDI every time it wishes to borrow money from the market or issue securities to the public.  (FindLaw, 2009) Before the sale of Home depot supply in

In Support of the Death Penalty Term Paper Example | Topics and Well Written Essays - 3750 words

In Support of the Death Penalty - Term Paper Example ing the debate at the international level on whether a country should have capital punishment fall into three broad categories, the morality of the death penalty, the inhuman nature of the death penalty, and the issue of the fairness of the judicial process. Many view the debate, which has left the world evenly divided on the issue, as a waste of effort unlikely to change strongly held views. However, with a closer examination of the opinions of elites in various countries and their influence on policy, one cant help but conclude that the weight of the arguments against capital punishment are dramatically shifting the momentum towards having governments around the world abolish or severely limit the use of the death penalty. The death penalty is validating due to one of the most important traditional thoughts which is retribution. â€Å"An eye for an eye† can express the unacceptable anger of victim’s family towards the homicides. The reason why a certain group of people believe that tooth for tooth because of the differentiate culture and values. The most populous country in the world, China, executes numerous people the past of thousands year just derived from an execution can brought closure to the trial for the victims family. As a matter of fact, there were 3400 people received the capital sentence in 2005 which was 90 percent of the total number of sentenced people globally. Importantly, however, the death penalty is much economical than its closest alternative -- life imprisonment with no parole. It is hard to set money aside for governments by using long term of sentence for prisoners who will spend the rest of their lives in jail. For this, the reason is that a great punishment will occupy 1.3 million dollars per case which is less than half as a thirty-year sentence. The death penalty should continue because it does not discriminate against the poor. Supporters argue that there is no excuse for inhuman behavior; society has no choice but to protect

Financial Ratios Analysis Essay Example | Topics and Well Written Essays - 750 words

Financial Ratios Analysis - Essay Example d. Cost of beverage sold percentage: Cost of beverage sold as percentage of total beverage sales. This works out to be 22.9%, which is within the range of industry average of 20-25%. Interestingly, the actual is very close to budgeted average of 22.5%. This shows that while management has made efforts to achieve what was budgeted, the efforts are certainly within the industry average. e. Average daily rate: This is taken as Room revenue to paid room nights. The paid room night is taken as 7555 and the average daily rate works out to be $62.7. As the value for previous year is not available, it is not possible to compare. f. Profit margin: This is income to revenue. The margin works out to be 56.4% of revenue. Profit margin has been worked out separately for room services and F&B. Profit margin for room service stands at 78.2%, which is marginally higher than the industry average of 70-75%. At the same time, F&B division has profit margin of 22% as against the industry average of 15-25%. g. Total revenue change from budget for rooms and F&B: This is actual revenue to budgeted revenue. This is almost one for F&B; but 0.88 for rooms. This is further corroborated by poorer occupancy rate. Marketing of room service is essential in this context. h. Housekeeping cost per occupied room: This is ratio of total housekeeping costs to total room sold. The actual is 6.5 which are substantially lower than budgeted 7.6. Thus, it appears that housekeeping costs has been controlled considerably. i. Room sales to total sales: This is a good indicator to gauge revenue generation by rooms. On the whole, room sales contributed 61.1% of total revenue. But this is found to be lower than budgeted 64.3%. This calls for some strategic intervention to boost up revenue collection from room service. Based on the above analysis, it can be concluded that F&B division has performed well in comparison

Writing a Critique Essay Example for Free

Writing a Critique Essay ‘To critique’ in the academic world means ‘to look into a certain work and state the strengths and weaknesses and then provide suggestions on improving the work in a manner that is constructive’ (Critiquing Tips, n.d.). Methods in Effectively Critiquing a Work Effectively critiquing a work entails the following: First of all, it is very important to be very honest (Critiquing Tips, n.d.). Second is to look for something optimistic or encouraging to speak about (Critiquing Tips, n.d.). Third is to speak about the weaknesses but at the same time â€Å"providing suggestions on how it may be developed and improved† (Critiquing Tips, n.d.). Last but not least, it is essential do be diplomatic no matter what weaknesses are to be stated and keep in mind that the goal of critiquing is to â€Å"provide assistance to the author of the work† and not attack or insult the individual (Critiquing Tips, n.d.). Aspects to Look for in Critiquing It is essential to look into the references utilized by the author, check for validity and reliability (Chesapeake College, n.d.). Scrutinize how the ideas were supported, check if the stated ideas are facts, or simply opinions to verify if there was no bias and both sides (or opposing perspectives) were evenly taken into consideration (Chesapeake College, n.d.). Also, the â€Å"appropriateness of the vocabulary and logic of the argument should be looked into as well† (Chesapeake College, n.d.). Noting the Findings/ Writing and Presenting the Critique The findings may be noted by: 1) â€Å"introducing the work including the author, title, as well as, the references and their dates of publication†; 2) â€Å"providing a one- to two- sentence summary†; and 3) â€Å"producing a thesis statement† (UHWO Writing Center, n.d.). It is also highly recommended to state â€Å"three to five points to support the thesis statement† (Chesapeake College, n.d.).

Mitigation of Health Risk of Women at Child-Bearing Age

Mitigation of Health Risk of Women at Child-Bearing Age Mitigation of Health Risk of Women at Child-Bearing Age Through Nutritional Patterns – Strategy Assumptions Basic assumptions for above mentioned Research The Research uses the findings of three own epidemiological surveys carried out in 1991, 1993, 2000 on nutritional pattern and nutritional status of pregnant and non-pregnant women at child-bearing age, which contain a lot of representative features on a national scale, for the development of strategy on further research in the surveyed area during second and third decade of 21st century. The findings were used as a inputs for development of preliminary diagnosis of current status and as assumptions for the strategy of modern research on early nutritional health risks of pregnant and non-pregnant women at child-bearing age. The Poland lacks diagnosis that would be based on representative national survey of women population falling into 15-49 age category with the application of all necessary methods used in descriptive, analytical and molecular epidemiology. The diagnosis seems to be indispensable. It was proven that in the last several decades most of nutrients served in the right quantities and proportions strengthen definitely the health condition of woman at child-bearing age and her foetus as well as genome stability. Own surveys of the author in this field are one of the most representative on a national scale in the last several decades. The dataset of 3177 all-day diets coming from three own surveys on nutritional pattern and anthropometric measurements of the nutritional status of non-pregnant women at child-bearing age collected in 1991-2000 and dataset of 1472 all-day diets of pregnant women are the most numerous of all surveys published in the last 25 years. The major lessons drawn from the preliminary diagnosis are as follows: * Substantiation that high percentage (>50.0% of all-day diet dataset) with the energy from total fats (above 35%) is chronic and was found out in each of the carried out surveys both in pregnant and non-pregnant women subpopulations. *It was proven that in the last survey it was accompanied by definite deficiency of long-chain n-3 polyunsaturated fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Far higher-than-tolerated (up to 7% of energy from all-day diet) was the share of energy from saturated fatty acids. This enhances unambiguously in the surveyed population a risk of lipid management disturbances, a risk of cardio-vascular system diseases and a risk of diabetes type 2 and obesity. * The sodium intake from all-day diet was proven to be twice as high as Adequate Intake (AI), in predominant number of all-day diets, both in pregnant and non-pregnant women subpopulations. It should be noted that sodium is one of highly significant diet-related risks causing, inter alia, hypertension. *The lower-than-recommended iodine content was found out in the diets (mainly in the diets of pregnant women population), thus enhancing a risk of thyroid gland malfunctions, and in the foetus and infant populations – also physical and mental disorders. *Low iron content was discovered in the diets of pregnant women, which is conducive to enhancement of anaemia risk caused by iron deficiency. It enhances risk of premature birth, low body mass at birth and reduced infant health condition. Iron deficiency during pregnancy reduces its reserves for the foetus and in the first year of life, and also has adverse impact on further development of infant and in subsequent years of life. * For the population of women at child-bearing age evidence was found of lower than adequate intake (AI) from diet, on a population scale: D vitamin, proven by analytical testing, during multi-site clinical tests, published in 2012. The findings also confirm high risk of bone mineral management disorders, development of rickets in children population and growing risk of osteoporosis development in middle aged population. *For non-pregnant and pregnant child-bearing women subpopulations the lower-than-adequate intake (AI) of calcium from diet was discovered, which given specifically low D vitamin content and high phosphorous content in food enhances risk of mineral management disorders, including in particular bone structure, as well as probable increase of obesity prevalence, caused by the deficiency of nutrient in question. During the first decade of 21st century the situation most probably did not change. *Lower-than-adequate intake (AI) from food, on a population scale, was discovered for: dietary fibre, mainly in the diets of non-pregnant women, which by all means enhances the risk of abdominal obesity and diabetes of type 2. *Far lower-than-recommended folates content in the diets of Polish women at child-bearing age was discovered. Additionally in some diets low content of riboflavin, B6 and B12 vitamins was discovered. The folate deficiencies found out in the diets of Polish women enhance a risk of neural tube defects in infant population and they also enhance a risk of genome stability disorders. *Ten nutritional health risks listed above for the population of women at child-bearing age were paralleled by growing prevalence of obesity, mainly in the surveyed women falling into 45+ age category: a percentage of obese women in the 15–44age category rose insignificantly (from6.4% in 1991 to 7.8% in 2000), a percentage of obese women in the 45–49age category declined insignificantly (from21.1% to 20.5%), a percentage of obese women above 50 years of age, also found out in the population surveys in question, rose significantly in statistical terms (from27.7% to 33.9%) (p = 0.074); Prevalence of 3rd degree of obesity in the overall population of adult women rose from 0.2% in 1991 to 0.9% in 2000 (p = 0.001) in the population of 2725 women surveyed in 1991 the obesity was found out in 10.1% of the surveyed, whereas in 2000in the population of 1695 women, in the same age bracket, obesity was found out in a significantly higher (p The presented findings of three surveys carried out in the population of women at child bearing age with the application of only descriptive epidemiology methods, with underrepresentation of samples, with parallel discovery of many flaws in nutritional pattern and nutritional status, give legitimacy to the conduct of a survey, that has not been conducted so far, with the application of descriptive, analytical and molecular methods. The inevitability of such approach to the survey with random sample selection on a nation-wide basis is indicated by the state-of-the-art in the fields of mother and foetus medicine, epigenetics and nutrigenomics. Based on survey findings the following conclusions were drawn: ** The found out, aforementioned most probably prevailing, modifiable, nutritional health and current nutritional status risks in the subpopulations of surveyed non-pregnant and pregnant women at child-bearing age is probably a material dataset of characteristics enhancing a risk of occurrence of homeostasis disorders, threatening the physiological course of pregnancy and the maintenance of health of foetus, infant and child in consecutive decades of her/his life. **Overweight and obesity, with growing prevalence with age, enhances probably in the population of non-pregnant women a risk of chronic, low level inflammation conducive, as shown by the analysis of bibliography, to the occurrence of insulin resistance, diabetes of type 2, damage of blood vessels’ endothelium, development of metabolic syndrome, congenital anomalies, and also through, inter alia, cytokines also probable genome stability disorders. A decisive increase of prevalence of obesity in Poland was recorded mainly in the population of women in the 44+ age category. The prevalence of overweight and obesity in the population of Polish women at child-bearing population may probably grow in decades to come due to, inter alia, disadvantageous demographic situation and insufficient efficiency of health-oriented changes in lifestyle of this subpopulation of women. Intervention measures applied have to be more effective than to date and they should start, at least, one year before fertilization. **The analysis of current state of knowledge, based on survey findings, on early prevention of diet-related diseases (on a population scale) leads to a fundamental conclusion that molecular epidemiology, using methods applied, inter alia, in functional genomics and in epigenetics, should be introduced to diagnose health condition of women at child-bearing age as a tool with the same value as descriptive and analytical epidemiology methods. The molecular epidemiology investigating, inter alia, the susceptibility of genes to food-related conditions, seems to be an irreplaceable tool in the early diagnosis of health condition of women population described in this monograph. The collected and processed in a complementary fashion survey findings in each of the three disciplines should lay foundations for taking early interventions in the field of preventive measures and early secondary measures counteracting health disorders and diet-related diseases caused by faulty nutritional pattern, in both distinguished physiological conditions. The parallel implementation of measures and methods in the three aforementioned areas, in appropriate proportions, in the field of epidemiological studies on nutritional pattern and nutritional status of surveyed non-pregnant and pregnant women population, in order to strengthen effectively this part of public health system, seems to arouse interest of the Ministry of Science and the Ministry of Health or their counterparts in most European Union Members States, and the interest of EFSA. **A number of material detailed findings, from cognitive and application perspectives, is provided in the individual sections of monograph.

Computers in the Mathematics Classroom :: Math Technology Education

?Calculators and computers are reshaping the mathematical landscape, and school mathematics should reflect those changes? (NCTM 24). My view of mathematics and geometry is that they go hand in hand. You have to know some algebraic procedures in order to be able to perform geometry problems. I never enjoyed Geometry in high school but now that I see it in a different prospective using GSP I really understand and enjoy it. I think that Geometry should be taught with software so the students can work with it hand in hand with the teacher and other students. Looking from the teacher prospective it would be easier to describe various concepts. To learn geometry means to know how to perform geometric problems and understand the process. I also think that a person should know various ways to perform geometry including the use of a calculator and Geometry Sketch Pad. One expectation of Geometry according the NCTM Standards is to ?draw and construct representations of twoand three-dimensional geometric objects using a variety of tools? (308). By using GSP the process is easier to follow 2 then just using a pencil and paper approach. Now don?t get me wrong using pencil and paper to draw various geometry objects is ways to have the student learn express relational understanding. Geometry Sketch Pad gives the user the option of reversing the steps to see were you started which could help to remember the process which is even more of a relational understanding. The user can also save his or her work for the future and the teacher is also able to see what the student?s train of thought. We need to use Dynamic Geometry Software in our teaching and learning so we can see and play with problems presented. By teaching with the use of Geometry Sketch Pad the teacher has the capabilities to teach outside of the book. It causes students to learn in a more relational way as apposed to instrumental (How Should Mathematics Be Taught?). By learning with the use of Geometry Sketch Pad a person is able to save their work for later reflections and they are able to learn a process. The capabilities of GSP are vast. The teacher and the learner both can benefit significantly through the use of GSP. I only foresee a little difference between the use of Dynamic Geometry Software in High school and in middle 3 school. I think at the high school level is where teachers