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dffded34c968-0 | Communication Networks | Page 1 |
9e23eabf1336-0 | McGraw-Hill Series in Computer Science SENIOR CONSULTING EDITOR C.L. Liu, University of Illinois at Urbana-Champaign CONSULTING EDITOR Allen B. Tucker, Bowdoin College Fundamentals of Computing and Programming Computer Organization and ArchitectureComputers in Society/EthicsSystems and LanguagesTheoretical FoundationsS... | Page 2 |
6da08886c042-0 | Communication Networks Fundamental Concepts and Key Architectures SECOND EDITION Alberto Leon-Garcia University of Toronto Indra Widjaja | Page 3 |
57ffc20e7dac-0 | COMMUNICATION NETWORKS: FUNDAMENTAL CONCEPTS AND KEY ARCHITECTURES SECOND EDITION Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc., 1221 Avenue of the Americas, New York, NY 10020. Copyright c/circlecopyrt2004, 2000 by The McGraw-Hill Companies, Inc. All rights reserved. No part of this publ... | Page 4 |
57ffc20e7dac-1 | Banowetz Senior media technology producer: Phillip Meek Designer: David W. Hash Cover image: CMU Network, c/circlecopyrtDawson 3D, Inc./Henk Dawson Compositor: Interactive Composition Corporation Typeface: 10.5/12 Times Printer: R. R. Donnelley Crawfordsville, IN Library of Congress Cataloging-in-Publication Data Leon-... | Page 4 |
da6fc3f35571-0 | Tomy teachers who taught me how to learn for the sake of learning, and to my students who taught me how to learn for the sake of teaching. —alg Tomy parents: with gratitude for your love and support. —iw | Page 5 |
722d5c5ede0b-0 | TABLE OF CONTENTS Preface xvii About the Authors xxvii 1 Communication Networks and Services 1 1.1 Evolution of Network Architecture and Services 2 1.1.1 Telegraph Networks and Message Switching 2 1.1.2 Telephone Networks and Circuit Switching 5 1.1.3 The Internet, Computer Networks, and Packet Switching 9 1.2 Future N... | Page 7 |
722d5c5ede0b-1 | TCP/IP Architecture 52 2.3.2 TCP/IP Protocol: How the Layers Work Together 55 2.3.3 Protocol Overview 61 ◆2.4 The Berkeley API 62 2.4.1 Socket System Calls 64 2.4.2 Network Utility Functions 68 ◆2.5 Application Layer Protocols and TCP/IP Utilities 77 2.5.1 Telnet 78 2.5.2 File Transfer Protocol 78 2.5.3 Hypertext Trans... | Page 7 |
973928714498-0 | viii Table of Contents 3 Digital Transmission Fundamentals 99 3.1 Digital Representation of Information 100 3.1.1 Block-Oriented Information 101 3.1.2 Stream Information 103 3.2 Why Digital Communications? 107 3.2.1 Comparison of Analog and Digital Transmission 107 3.2.2 Basic Properties of Digital Transmission Systems... | Page 8 |
973928714498-1 | 3.8 Properties of Media and Digital Transmission Systems 146 3.8.1 Twisted Pair 148 3.8.2 Coaxial Cable 152 3.8.3 Optical Fiber 156 3.8.4 Radio Transmission 162 3.8.5 Infrared Light 166 3.9 Error Detection and Correction 166 3.9.1 Error Detection 167 3.9.2 Two-Dimensional Parity Checks 171 3.9.3 Internet Checksum 172 3... | Page 8 |
71f4554d0262-0 | Table of Contents ix 4 Circuit-Switching Networks 206 4.1 Multiplexing 207 4.1.1 Frequency-Division Multiplexing 208 4.1.2 Time-Division Multiplexing 209 4.1.3 Wavelength-Division Multiplexing 212 4.2 SONET 213 4.2.1 SONET Multiplexing 214 4.2.2 SONET Frame Structure 216 4.3 Transport Networks 221 4.3.1 SONET Networks ... | Page 9 |
71f4554d0262-1 | Overload Controls 261 4.8 Cellular Telephone Networks 263 Summary 270 Checklist of Important Terms 270 Further Reading 271 Problems 272 5P eer-to-Peer Protocols and Data Link Layer 282 Part I: Peer-to-Peer Protocols 283 5.1 Peer-to-Peer Protocols and Service Models 284 5.1.1 Service Models 284 5.1.2 Examples of Service... | Page 9 |
06869848c425-0 | xT able of Contents Part II: Data Link Controls 324 5.4 Framing 325 5.5 Point-to-Point Protocol 329 5.6 HDLC Data Link Control 333 5.6.1 Data Link Services 333 5.6.2 HDLC Configurations and Transfer Modes 335 5.6.3 HDLC Frame Format 335 5.6.4 Typical Frame Exchanges 337 ◆5.7 Link Sharing Using Packet Multiplexers 340 5.... | Page 10 |
06869848c425-1 | Access Control 387 6.3.1 Reservation Systems 388 6.3.2 Polling 390 6.3.3 Token-Passing Rings 393 6.3.4 Comparison of Scheduling Approaches in Medium Access Control 396 6.3.5 Comparison of Random Access and Scheduling Medium Access Controls 397 ◆6.4 Channelization 398 6.4.1 FDMA 399 6.4.2 TDMA 400 6.4.3 CDMA 401 6.4.4 C... | Page 10 |
0057751d6ef3-0 | Table of Contents xi Part II: Local Area Networks 421 6.6 LAN Protocols 421 6.6.1 LAN Structure 422 6.6.2 The Medium Access Control Sublayer 423 6.6.3 The Logical Link Control Sublayer 425 6.7 Ethernet and IEEE 802.3 LAN Standard 427 6.7.1 Ethernet Protocol 427 6.7.2 Frame Structure 429 6.7.3 Physical Layers 431 6.7.4 ... | Page 11 |
0057751d6ef3-1 | Source Routing Bridges 474 6.11.3 Mixed-Media Bridges 477 6.11.4 Virtual LANs 477 Summary 479 Checklist of Important Terms 480 Further Reading 481 Problems 482 7P acket-Switching Networks 490 7.1 Network Services and Internal Network Operation 492 7.2 Packet Network Topology 496 7.3 Datagrams and Virtual Circuits 501 7... | Page 11 |
b6bc6e166b69-0 | xii Table of Contents 7.5 Shortest-Path Routing 522 7.5.1 The Bellman-Ford Algorithm 523 7.5.2 Dijkstra’s Algorithm 530 7.5.3 Source Routing versus Hop-by-Hop Routing 532 7.5.4 Link-State Routing versus Distance-Vector Routing 533 7.6 ATM Networks 534 7.7 Traffic Management at the Packet Level 539 7.7.1 FIFO and Priorit... | Page 12 |
b6bc6e166b69-1 | IP Routing 583 8.2.5 Classless Interdomain Routing (CIDR) 584 8.2.6 Address Resolution 585 8.2.7 Reverse Address Resolution 587 8.2.8 Fragmentation and Reassembly 587 8.2.9 ICMP: Error and Control Messages 589 8.3 IPv6 592 8.3.1 Header Format 593 8.3.2 Network Addressing 594 8.3.3 Extension Headers 597 8.3.4 Migration ... | Page 12 |
de473047a614-0 | Table of Contents xiii 8.6 Internet Routing Protocols 620 8.6.1 Routing Information Protocol 621 8.6.2 Open Shortest Path First 622 8.6.3 Border Gateway Protocol 631 8.7 Multicast Routing 640 8.7.1 Reverse-Path Broadcasting 641 8.7.2 Internet Group Management Protocol 643 8.7.3 Reverse-Path Multicasting 644 8.7.4 Dista... | Page 13 |
de473047a614-1 | Traffic Contracts, Connection Admission Control, and Traffic Management 673 9.4 ATM Adaptation Layer 674 9.4.1 AAL1 675 9.4.2 AAL2 678 9.4.3 AAL3/4 680 9.4.4 AAL5 683 9.4.5 Signaling AAL 684 9.4.6 Applications, AALs, and ATM Service Categories 686 9.5 ATM Signaling 688 9.5.1 ATM Addressing 688 9.5.2 UNI Signaling 690 9.5... | Page 13 |
434ef2c09c70-0 | xiv Table of Contents 10 Advanced Network Architectures 705 10.1 Integrated Services in the Internet 706 10.1.1 Guaranteed Service 707 10.1.2 Controlled-Load Service 708 10.2 RSVP 708 10.2.1 Receiver-Initiated Reservation 710 10.2.2 Reservation Merging 711 10.2.3 Reservation Styles 712 10.2.4 Soft State 714 10.2.5 RSVP... | Page 14 |
434ef2c09c70-1 | 10.5.7 GMPLS 738 10.6 Real-Time Transport Protocol 740 10.6.1 RTP Scenarios and Terminology 741 10.6.2 RTP Packet Format 743 10.6.3 RTP Control Protocol (RTCP) 745 10.7 Session Control Protocols 747 10.7.1 Session Initiation Protocol 747 10.7.2 H.323 Multimedia Communication Systems 751 10.7.3 Media Gateway Control Pro... | Page 14 |
c223158c87e5-0 | Table of Contents xv 11.2.3 Setting Up a Security Association 778 11.2.4 IPSec 780 11.2.5 Secure Sockets Layer and Transport Layer Security 782 11.2.6 802.11 and Wired Equivalent Privacy 788 11.3 Cryptographic Algorithms 790 11.3.1 DES 790 11.3.2 RSA 793 Summary 794 Checklist of Important Terms 795 Further Reading 796 ... | Page 15 |
c223158c87e5-1 | 830 Further Reading 830 Problems 831 Epilogue 837 Appendices A Delay and Loss Performance 840 A.1 Delay Analysis and Little’s Formula 840 A.1.1 Arrival Rates and Traffic Load Definitions 841 A.1.2 Little’s Formula 842 A.2 Basic Queueing Models 845 A.2.1 Arrival Processes 846 A.2.2 Service Times 846 A.2.3 Queueing System ... | Page 15 |
2d7d47440497-0 | xvi Table of Contents A.3 M/M/1: A Basic Multiplexer Model 849 A.3.1 M/M/1 Steady State Probabilities and the Notion of Stability 850 A.3.2 Effect of Scale on Performance 853 A.3.3 Average Packet Delay in a Network 854 A.4 The M/G/1 Model 854 A.4.1 Service Time Variability and Delay 855 A.4.2 Priority Queueing Systems ... | Page 16 |
2a9ecc32dd6e-0 | PREFACE OBJECTIVE Communication networks are in a period of transition from networks that are based on telephone architecture and standards to networks based on the Internet Protocol (IP)architecture. The main reason for this change is that new services and applications canbe deployed with unprecedented speed over an I... | Page 17 |
2a9ecc32dd6e-1 | the functionality of the cellular and telephone network will be replaced by moreversatile signaling based on Internet protocols. A new generation of IP-based protocolswill control and manage the resources in the next generation of networks. It is in this exciting context of new services and emerging next-generation net... | Page 17 |
f5f4b3094031-0 | xviii Preface As prerequisites the book assumes a general knowledge of computer systems. In certain optional parts of the text, knowledge of programming, elementary probability, or elementary calculus is required. These sections are clearly indicated and can beskipped. APPROACH AND CONTENT The book is organized into th... | Page 18 |
f5f4b3094031-1 | an example of a peer-to-peer protocol and thenwe discuss its application in TCP reliable stream service and flow control. We coverthe essential computer network topics, but we also have extensive discussion of accessand transport networks, telephone and cellular services and signaling. This additionalmaterial is organiz... | Page 18 |
8187c1856945-0 | Preface xix Part III. Key architectures, advanced topics, and next generation networks (Chapters 8–12 and Appendices): •IPv4 and IPv6; TCP, UDP; RIP, OSPF, BGP; DHCP and mobile IP •ATM networks •New Architectures: IntServ, RSVP, DiffServ, Peer vs. Overlay Interconnection, MPLSand GMPLS, RTP, SIP, and H.323 •Network Sec... | Page 19 |
8187c1856945-1 | of captured traffic at layers 2 and above at any level of detail. We use Etherealin the following ways: •Examples of Ethereal packet captures demonstrate the operation of protocols such asHTTP, SMTP, Telnet, SIP, RSVP, RTP, DNS, TCP, UDP, OSPF, IP, ARP, Ethernet,802.11, PPP, LCP, IPCP, SSL, and TLS. •Weprovide instructo... | Page 19 |
217516dd3c6f-0 | xx Preface •In Chapter 2 the discussion on how all the layers work together has been improved by introducing examples using Ethereal packet captures. The section on applicationlayer protocols has been expanded and a new section provides an introduction tonetwork protocol analyzers. •PCM speech coding has been moved fro... | Page 20 |
217516dd3c6f-1 | of the overlay and peermodels to network interconnection. The chapter now contains discussion on virtualnetworks and GMPLS. The material on RTP and SIP has been updated and movedfrom Chapter 12 to this chapter. •Chapter 11 has been updated with brief discussions of the Advanced EncryptionStandard and 802.11 security. C... | Page 20 |
3295a3318db0-0 | Preface xxi Appendix A Queueing Models1.1–1.2 Network Evolution 1.3 Evolution Factors 2.1–2.3 Layered Architecture Overview of TCP/IP 2.4 Sockets2.5 Application Layer and Utilities 3.1–3.2 Digital Inform ation and Digital Transm ission3.3–3.5 Digital Inform ation, Channels, and DigitalTransmission3.6–3.7 Line Coding... | Page 21 |
3295a3318db0-1 | Network Secur ity 12. Mult imedia I nformation 10. Advanced Architectures(8.2–8.3)(10.4)8.7–8.8 Multicast Routing,DHCP, Mobile IP(6.11.2)5.6 HDLC 5.7 Link Sharing 6.3 Scheduling6.4 Channelization4.7 Telephone Traffic4.8 Cellular Networks Appendix B Ne twork Management9. ATM Architecture 8.1–8.6 TCP/IP Architecture FIGU... | Page 21 |
983c2a0c6ae5-0 | xxii Preface PEDAGOGICAL ELEMENTS Wehave improved the pedagogical elements of the first edition and offer several new elements. •Ethereal Virtual Lab. Lab experiments are the most effective means for reinforcing the concepts taught in lectures. At the physical layer a rich set of instruments (for example, oscilloscopes,... | Page 22 |
f380d22f2228-0 | Preface xxiii after the student clicks on a web link: A DNS query and response; A TCP three-way connection setup; an HTTP request, followed by a TCP acknowledgment, and then thebeginning of the HTTP response. The sequence of packets exchanged for various typesof protocols can be analyzed in this fashion. The middle pan... | Page 23 |
f380d22f2228-1 | traceroute, which can be used in exercises that involve Ethereal packet captures. •Numerous figures. Network diagrams, time diagrams, performance graphs, state tran- sition diagrams are essential to effectively convey concepts in networking. •Lecture charts. Wehave prepared approximately 500 MS PowerPoint ®charts for us... | Page 23 |
f380d22f2228-2 | material covered in the chapter and in the context of the “big picture.” •Chapter summaries and checklist of important terms. Each chapter includes a sum- mary that reiterates the most important concepts. A checklist of important terms aidsthe student in reviewing the material. •Mathematical sections. In general key ma... | Page 23 |
321e27801a34-0 | xxiv Preface to appropriate Internet Engineering Taskforce (IETF) RFCs and research papers is made where appropriate, especially with more recent topics. •A website. The following website www.mhhe.com/leon-garcia contains links to the following teaching resources: •AnInstructor’s Solutions Manual •Additional problems, ... | Page 24 |
321e27801a34-1 | Mitra for their continued encouragement and interest in the book.Wethank Yau-Ren Jenq for reviewing the fair queueing discussions in detail. Weare especially grateful to Irene Katzela for testing the manuscript in her courses. Wealso thank Ray Pickholtz for testing various versions of the text, including the beta versi... | Page 24 |
321e27801a34-2 | Jim Yan formany illuminating conversations over the years. We especially thank Tony Yuen forsharing his vast knowledge of the networking industry and for continuously showinghow the big picture is actually bigger! Fortheir help with the preparation of the second edition we would like to thank the following reviewers: M... | Page 24 |
8f41dbe15a09-0 | Preface xxv (University of Lund), LeRoy W. Bearnson (Brigham Young University), Michael J. Donahoo (Baylor University), Yuguang Fang (University of Florida), Jeff Fedor (Uni-versity of Southern California), Jeremiah F. Hayes (Concordia University), Mike Kain(Drexel University/Unisys Corporation), W. David Laverell (Cal... | Page 25 |
8f41dbe15a09-1 | and MuhamedDurani for sharing their knowledge of Ethereal with us. We are also grateful for varioustechnical interactions we had with colleagues at Fujitsu: Yau-Ren Jenq, Edmund Cher,Amalendu Chatterjee, Anna Cui, Steven Wright, and Masafumi Katoh; and at BellLabs: Iraj Saniee, Yikai Su, Debasis Mitra, Anwar Elwalid, C... | Page 25 |
8f41dbe15a09-2 | we have tried to make the complex and fluid topic of network architecture as approachable, up-to-date, and error-free as possible. Wewelcome all comments and suggestions on how to improve the text. Please contact usvia the text’s website with any ideas you may have. Alberto Leon-Garcia Indra Widjaja | Page 25 |
5edcd0dad77c-0 | ABOUT THE AUTHORS Alberto Leon-Garcia is a Professor in the Department of Electrical and Computer Engineering at the University of Toronto where he holds the Jeffrey Skoll Chair in Computer Networks and Innovation. He was also Chief Technical Officer and co-founder of AcceLight Networks Inc. where he led the development... | Page 27 |
5edcd0dad77c-1 | research interests include traffic engineering, architectures for cost-effective transport networks, and high-speed packet switching. He has extensive publication in technical journals and conferences and holds several patents in switchingarchitectures. He is also an active member of IETF and IEEE. In 1993, Dr. Widjaja ... | Page 27 |
99eeee3a5a64-0 | CHAPTER 1 Communication Networks and Services Acommunication network, in its simplest form, is a set of equipment and facilities that provides a service: the transfer of information between users located at various geographical points. The most familiar example of a communication network is the tele- phone network, whi... | Page 29 |
99eeee3a5a64-1 | allows users to gather information in large volumes nearly instantaneously and, with the aid of computers, to almost immediately exercise action at a distance. These two unique capabilities form the basis for many emerging servicesand an unlimited number of future network-based services. For example, the Internetcurren... | Page 29 |
633dfb08422f-0 | 2 CHAPTER 1 Communication Networks and Services The purpose of this chapter is to explain how the design or “architecture” of a network is influenced by the services that it supports. In Section 1.1 we consider the evolution of three example networks and their associated services. This discussion serves to identify the ... | Page 30 |
633dfb08422f-1 | last 150 years. In this time we have gone from telegraphsystems that operated at tens of bits/second to modern optical systems that operate atterabits/second. 1.1.1 Telegraph Networks and Message Switching In 1837 Samuel B. Morse demonstrated a practical telegraph that provided the basis fortelegram service, the transm... | Page 30 |
ae8e45335104-0 | 1.1 Evolution of Network Architecture and Services 3 TABLE 1.1 International Morse code. Morse Code Morse Code Morse Code Morse Code A ·—J ·——— S ··· 2 ··——— B— ··· K— ·—T — 3 ···—— C— ·—· L ·—·· U ··—4 ····— D— ·· M— — V ···—5 ····· E · N— · W ·—— 6 — ···· F ··—· O ——— X — ··—7 — — ··· G— — · P ·——· Y— ·—— 8 ——— ·· H ... | Page 31 |
ae8e45335104-1 | address. The operator would store the message until the desired communication line became available and then would forward the message to the next appropriate station. This store-and-forward process would be repeated at each intermediate station until the message arrived atthe destination station. Message switching is ... | Page 31 |
ae8e45335104-2 | system eventually led to the modern practice of representing alphanu- meric characters by groups of binary digits as in the ASCII code (short for AmericanStandard Code for Information Interchange). Table 1.2 shows the binary representationfor a subset of the ASCII code. The Baudot system also eventually led to the de-v... | Page 31 |
700fa42fd884-0 | 4 CHAPTER 1 Communication Networks and Services TABLE 1.2 Subset of ASCII character set and their binary representation. Binary Char Binary Char Binary Char 0000000 NUL 0110000 0 1000001 A 0000001 SOH 0110001 1 1000010 B 0000010 STX 0110010 2 1000011 C 0000011 ETX 0110011 3 1000100 D 0000100 EOT 0110100 4 1000101 E 000... | Page 32 |
700fa42fd884-1 | symbols could be transmitted simultaneously by using multiplepairs of frequencies for the various telegraphy signals. These modulation techniquesformed the basis for today’s modems. Prior to the invention of telegraphy, long-distance communication depended pri- marily on messengers that traveled by foot, horse, or othe... | Page 32 |
700fa42fd884-2 | Morse code, or “zero” and “one” in the case of Baudot or ASCII code. The transmission medium can be copper wire,radio, or smoke signals for that matter. 2 1The speed of light in a vacuum is 3 ×108meters/second; in cable, it is 2.3 ×108meters/second; in optical fiber, it is 2 ×108meters/second. 2Indeed in the 1700s “visu... | Page 32 |
04b78c23d7fa-0 | 1.1 Evolution of Network Architecture and Services 5 2. A framing method is required for indicating the beginning and end of messages and for taking the sequence of dots/dashes or zeros/ones and grouping them into characters, and in turn, meaningful messages. 3. A system for specifying the destination address of messag... | Page 33 |
04b78c23d7fa-1 | in the business and later inresidential markets. The deployment of telephones grew quickly, from 1000 phones in1877 to 50,000 in 1880 and 250,000 in 1890. Connectivity in the original telephone system was provided by an analog transmission system. The transmitted electrical signal is analogous to the original voice sig... | Page 33 |
7730942f9fff-0 | 6 CHAPTER 1 Communication Networks and Services (b)(a) User 1 User 2 User N (c)FIGURE 1.3 Telephone network: (a) dedicated resources require numerous lines; (b) a switch in theform of an operator with a patch cordpanel; (c) cords interconnecting usersockets providing end-to-endconnection. In its simplest form, the tele... | Page 34 |
7730942f9fff-1 | connection. This connection is maintained for the duration of the call. Oncethe connection is established the second phase (information transfer) begins. When theusers are done with their conversation, they “hang up” their telephones, which generatesa signal indicating that the call is complete. At this point, the thir... | Page 34 |
a90db03ab39c-0 | 1.1 Evolution of Network Architecture and Services 7 Toll CO CO CO CO COTandem TandemCO /H11005 central office FIGURE 1.4 Hierarchical telephone network structure. interconnected and organized in a hierarchical network, with customers attaching to end offices, which in turn are connected to tandem offices and so forth as... | Page 35 |
a90db03ab39c-1 | the actual transfer of information can take place. Thetransfer mode of a network that involves setting up a dedicated end-to-end connectionis called circuit switching. Note that in circuit switching the routing decision is made when the path is set up in switching and transmission equipment across the network.After the... | Page 35 |
819853d81aa9-0 | 8 CHAPTER 1 Communication Networks and Services 1. The caller picks up the phone triggering the flow of current in wires that connect to the telephoneoffice.Connection set upInformation transfer2. The current is detected, and a dial tone istransmitted by the telephone office to indicate thatit is ready to receive the d... | Page 36 |
819853d81aa9-1 | mission systems had to interface to existing analog switches. Upon arrival at an analogswitch, the digital signal would be reconverted into analog voice signals for switchingand then reconverted to digital form for transmission in the next hop. This inefficiencywaseliminated by the deployment of digital switches in the ... | Page 36 |
f84deb8d7844-0 | 1.1 Evolution of Network Architecture and Services 9 between the computers that controlled these switches. In addition to setting up calls, the signaling network enabled the introduction of new services such as credit card calls,long-distance calls, 800 calls, call screening, voice mail, and many other services. A majo... | Page 37 |
f84deb8d7844-1 | be analog or digital depending on the attached transmission system. The tandem connection of transmission lines andtelephone switches form the end-to-end circuit that transfers the voice signal. 3. A telephone numbering system to identify telephone users or stations. 4. Methods for allowing users to indicate to the net... | Page 37 |
f84deb8d7844-2 | provides datagram service, namely, the transfer of “packets”of information across multiple, possibly dissimilar networks. Before discussing packet switching and the architecture of the Internet, we need to present some of the types ofnetworks that the Internet operates on. We also retrace the development of computernet... | Page 37 |
99376f1f10c7-0 | 10 CHAPTER 1 Communication Networks and Services The first computer network was the Semi-Automatic Ground Environment (SAGE) system developed between 1950 and 1956 for air defense systems [Green 1984]. The system consisted of 23 computer networks, each network connecting radar sites, ground-to-air data links, and other ... | Page 38 |
99376f1f10c7-1 | overawide geographical area. 4Weemphasize the fact that the “users” of this network were full-fledged computers, not terminals. As such, the users of this networkhad processing and storage resources not available in previous terminal equipment. Ittherefore became possible to develop powerful networking protocols that ma... | Page 38 |
99376f1f10c7-2 | shows a typical exchange of messages that occurs when you call the telephone company to find a phone number. Theinteraction begins with the user dialing for directory assistance (411). The telephonenetwork responds with an automated welcoming message followed by a request forthe city (and state or province depending on ... | Page 38 |
c647186332ae-0 | 1.1 Evolution of Network Architecture and Services 11 “Do you have a first name or street?”Caller “Simpson”Caller replies System replieswith numberSystem replies System replies System replies Operator replies“Thank you, please hold” “Evergreen Terrace”CallerrepliesDials 411 “What city”? Callerreplies OperatorrepliesCa... | Page 39 |
c647186332ae-1 | browsing the HyperText Transfer Protocol (HTTP) specifies how a web client and server areto interact. Other examples of protocols are: File Transfer Protocol (FTP) for thetransfer of files, Simple Mail Transfer Protocol (SMTP) for e-mail, Internet Protocol(IP) for the transfer of packets, and Domain Name System (DNS) for... | Page 39 |
a9158b4ca7d0-0 | 12 CHAPTER 1 Communication Networks and Services (a) (b)CT T … C TTC /H11005 computer T /H11005 terminal Modem poolModemTT … Telephone network FIGURE 1.7 Terminal-oriented networks: (a) time-shared computers and cables for input devices; (b) dial-in. TERMINAL-ORIENTED NETWORKS Figure 1.7a shows an arrangement that allo... | Page 40 |
a9158b4ca7d0-1 | the same computer. In most of these appli-cations, the terminals would generate messages in a burstymanner; that is, the message transmissions would be separated by long idle times. The cost of providing individuallines to each terminal could be prohibitive, so various systems were developed to providea message transfe... | Page 40 |
fa2bf6546a2b-0 | 1.1 Evolution of Network Architecture and Services 13 HostInformation Address CRC Information Address CRCT T TMux … FIGURE 1.9 Multiplexer systems. listen to the outgoing line, but only the terminal that is polled replies by sending any information that it has ready for transmission on the incoming line. Statistical mu... | Page 41 |
fa2bf6546a2b-1 | impulses generated by analog switching equipment, and thermal noise inherentin electronic equipment. Error-control techniques were developed to ensure virtually error-free communication of data information. In addition to the header, each frame ofinformation would have a number of redundant CRC or “check bits” appended... | Page 41 |
49cd6a31b0f7-0 | 14 CHAPTER 1 Communication Networks and Services using lower-speed lines from various sites in its region. Multidrop lines such as those discussed above could be used in such lines, for example, Atlanta in the figure. Notethat routing and forwarding are straightforward in these tree-topology networks as allinformation fl... | Page 42 |
49cd6a31b0f7-1 | connected to the network.This function is similar to the message switching service provided by telegraph systems.An additional requirement of a computer network is that transit times be short for mes-sages from interactive applications. This requirement suggests that a limit be imposedon the size of messages that are a... | Page 42 |
a9e5a5019dc0-0 | 1.1 Evolution of Network Architecture and Services 15 AMES UCLAMCCLELLAN RANDUTAH TINKERBOULDER BBNGWC HARVCASE NBSETACMITRECARN MITLINCRADC SCDUSCILL AMES STANUCSB FIGURE 1.12 ARPANET circa 1972 [Kahn 1972]. packets are transferred from packet switch to packet switch until they are delivered at the destination. The me... | Page 43 |
a9e5a5019dc0-1 | computers over wide geographical distances. 6 The packet switches were implemented by dedicated minicomputers, and each packetswitch was connected to at least two other packet switches to provide alternative paths incase of failures. The communications lines were leased from public carriers and initiallyhad a speed of ... | Page 43 |
ba4cd10bb000-0 | 16 CHAPTER 1 Communication Networks and Services Each packet switch maintained a routing table that would specify the output line that was to be used for each given destination. Packets were then buffered to await transmissionon the appropriate link. Packets from different users would thus be multiplexed into thelinks ... | Page 44 |
ba4cd10bb000-1 | contained a limited amount of buffering for holding packets. To prevent packet switches from becoming congested, an end-to-endcongestion control wasdeveloped. Operating between the source and destination packet switching nodes, the congestion control limited the number of packets that a host canhave in transit. In addi... | Page 44 |
ba4cd10bb000-2 | inside of frames that con- tain delineation information as well as check bits for error control. 3. Destinations are identified by unique addresses that are used by routing tables to perform routing decisions to select the next hop of each packet as it traverses the network. 4.Routing tables at the packet switches are c... | Page 44 |
2c66bee83b0e-0 | 1.1 Evolution of Network Architecture and Services 17 5.Messages are segmented into packets at the ingress to the network and reassembled at the egress of the network. End-to-end congestion control mechanisms are used to prevent congestion inside the network by limiting the number of packets a host can have in transit.... | Page 45 |
2c66bee83b0e-1 | at which messages are sent to match the abilityof the destination computer to process messages. The resulting computer network inturn enables the running of applications over geographically separate computers. InChapter 2 we will examine the layered structure of network architectures in detail. Local Area Networks The ... | Page 45 |
2c66bee83b0e-2 | topologies can provide thebroadcasting feature required by LANs, including ring, bus, and tree networks. The most successful LAN, the Ethernet shown in Figure 1.13a, involved transmis- sion over a bus topology coaxial cable. Stations with messages to transmit would first 7The missing element is that of an internetwork, ... | Page 45 |
406e3309187a-0 | 18 CHAPTER 1 Communication Networks and Services (a) (b)Transceivers FIGURE 1.13 Ethernet local area network: (a) bus topology; (b) star topology. sense the cable (carrier sensing) for the presence of ongoing transmissions. If no trans- missions were found, the station would proceed to transmit its message encapsulated... | Page 46 |
406e3309187a-1 | message-transfer service between computers and other devices that are attached to the LAN. The elements of LAN architecture involve: 1. A high-speed (typically 10 megabits/second and above) digital transmission system that may support broadcast transmissions. 2. An addressing structure that provides each station with a... | Page 46 |
9dea50443213-0 | book 1.1 Evolution of Network Architecture and Services 19 G /H11005 gateway/router H /H11005 host G G GGGG HHH HNet 5 Net 4Net 3 Net 2Net 1 FIGURE 1.14 An internetwork. lying technology and operation. For example, these networks could consist of various types of LANs, packet-switching networks, or even individual poin... | Page 47 |
9dea50443213-1 | service provided by IP is unreliable. Thestudent may wonder why one would want to build an internetwork to provide unreliableservice. The reason is that providing reliability inside the internetwork introduces a greatdeal of complexity in the routers. The requirement that IP operate over any networkplaces a premium on ... | Page 47 |
3221a29a5717-0 | 20 CHAPTER 1 Communication Networks and Services The Internet also provides a name space to refer to machines connected to the Internet, for example, tesla.comm.toronto.edu . The name space also has a hierarchical structure, butiti sadministrative and not used in the routing operation of the network. Automatic translat... | Page 48 |
3221a29a5717-1 | is relegated to the edge of the network, where it can be implementedin the host computers. A rich set of applications has been developed to operate on top of the TCP/IP. These applications include SMTP for e-mail service, FTP for file transfer, HTTP forweb service, and RTP for real-time transfer of information such as v... | Page 48 |
3221a29a5717-2 | its subsequent extensions/follow-ons. b.Is able to support communications using the Transmission ControlProtocol/Internet Protocol (TCP/IP) suite or its subsequentextenstions/follow-ons, and/or other IP-compatible protocols. c. Provides, uses, or makes accessible, either publicly or privately, high-level services layer... | Page 48 |
40b5c9c6c9f0-0 | 1.1 Evolution of Network Architecture and Services 21 WHAT IS A DOMAIN NAME? While each machine on a network has an IP address, this address usually provides little information on the use of the machine or who its owner is. To make the addressesmore meaningful to people, host names were introduced. For example, the IP ... | Page 49 |
40b5c9c6c9f0-1 | lines for the transfer of streams of binary information between equipment. 2. Exchange of frames of information between adjacent equipment; these frames contain delineation information as well as check bits for error control. 3.Medium access control procedures to regulate the transmission of frames from multiple users ... | Page 49 |
dcf1a1a959d0-0 | 22 CHAPTER 1 Communication Networks and Services transmission to enable the transfer of blocks of information across a transmission line. Another example involves an application building on top of a network informationservice. For example, the HTTP application builds on top of TCP/IP to deliver the web-browsing service... | Page 50 |
dcf1a1a959d0-1 | For example, the introduction of the electrical telegraphled to the disappearance of the visual telegraph networks within a few years. We havealso seen that a new architecture can grow steadily over many decades eventuallydisplacing an older architecture. For example, the gradual global deployment of thetelephone netwo... | Page 50 |
dcf1a1a959d0-2 | of messages between computers. Applicationsthat are taken for granted today, e-mail for example, came into wide use only in the | Page 50 |
da1180e7a1cc-0 | 1.2 Future Network Architectures and Their Services 23 recent past because of the Internet. Other applications, such as the World Wide Web and Napster, underwent explosive growth and had dramatic impact on business, commerce,education, and entertainment. We can expect that new generations of applications willcontinue t... | Page 51 |
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