Contents Introduction to TCP/IP Preface ..................................................................................i Prerequisites ........................................................................................i Key Topics ...........................................................................................i Course Objectives ...............................................................................ii Pedagogical Features ..........................................................................ii Learning Objectives, Unit Summaries, Discussion Questions, and Activities/Exercises ..................................................................iii Key Terms ..........................................................................................iii Supplements ......................................................................................iii Advancing Your Level of Technical Expertise .................................. iv Why Choose WestNet? ..................................................................... iv

Introduction .................................................................... xxiii Overview of Architectures .............................................................xxiii

Unit 1 TCP/IP Structure and Addressing ........................................1 Lesson 1 OSI Model Review .................................................................9 Primary Functions of the OSI Model Layers ...................................... 9 Physical Addresses ..................................................................... 10 The Physical Layer .............................................................. 11 The Data Link Layer ........................................................... 11 Logical Addresses ....................................................................... 11 The Network Layer ............................................................. 11 The Transport Layer ........................................................... 13 Layers 5 Through 7 ................................................................... 13 The Session Layer ............................................................... 14 The Presentation Layer ....................................................... 14 v

Introduction to TCP/IP The Application Layer ........................................................ 14 Addressing Summary ....................................................................... 14 Activities ........................................................................................... 15

Lesson 2 Internet Protocol Suite .........................................................17 Overview of the TCP/IP Protocol Suite ............................................ 17 Network Interface Layer Protocols ............................................ 18 Internetwork Layer Protocols .................................................... 18 Transport Layer Protocols ......................................................... 19 Application Layer Protocols ...................................................... 20 Communication Using TCP/IP ........................................................ 21 Application Layer ...................................................................... 21 Transport Layer ......................................................................... 22 Network Layer ........................................................................... 22 Network Interface Layer ............................................................ 23 Destination Station ................................................................... 23 Activities ........................................................................................... 24

Lesson 3 Internet Addressing .............................................................27 IP Addresses ...................................................................................... 27 Class A Address .......................................................................... 28 Class B Address .......................................................................... 29 Class C Address ......................................................................... 29 Class D Address ......................................................................... 30 Class E Address .......................................................................... 30 Address Format ................................................................................. 30 Dotted Decimal Notation .......................................................... 31 Addressing Rules .............................................................................. 31 Sample Network Using Class A Address Format .............................. 34 Activities ........................................................................................... 35

Lesson 4 Internetworking Devices ......................................................37 Common Network Components ..................................................... 38 NIC ............................................................................................ 38 Repeaters ................................................................................... 39 Hubs .......................................................................................... 40 Bridges ....................................................................................... 41 Switches ..................................................................................... 42 Routers ....................................................................................... 43 Broadcast Isolation ............................................................. 45 Making Forwarding Decisions ............................................ 46 Activities ........................................................................................... 47

Summary .............................................................................50 Quiz ....................................................................................52

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Unit 2 Overview of TCP/IP Applications ......................................57 Lesson 1 Summary of TCP/IP Applications ..........................................63 Accessing TCP/IP Applications ......................................................... 63 Common TCP/IP Applications ........................................................ 64 Browsers (HTTP) ........................................................................ 64 Telnet ......................................................................................... 65 FTP ............................................................................................. 65 TFTP ........................................................................................... 65 NNTP ......................................................................................... 65 E-Mail ........................................................................................ 66 Network Management .............................................................. 66 DNS ............................................................................................ 67 BOOTP ....................................................................................... 67 DHCP ......................................................................................... 67 Different Applications Use Different Protocols ............................... 68 Activities ........................................................................................... 71

Lesson 2 Web Browsers and Servers ...................................................73 Browsers and Servers Overview ........................................................ 73 Web Browsers ............................................................................ 76 Browser Basics .................................................................... 76 Activities ........................................................................................... 79

Lesson 3 Telnet ..................................................................................82 Common Telnet Uses ....................................................................... 82 How to Use Telnet by Means of a Command Line .......................... 83 Using Telnet With Windows .................................................... 84 Using Telnet by Means of a Web Browser ....................................... 86 Activities ........................................................................................... 87

Lesson 4 FTP ......................................................................................89 Why Use FTP? .................................................................................. 89 Purpose of Browser and Server Software .......................................... 90 Where Can We Use FTP? ........................................................... 90 Is Anonymous FTP Really Anonymous? ................................... 91 How Can We Use FTP? .............................................................. 91 Using Command Line FTP ............................................................... 91 Using FTP With a Browser ............................................................... 94 Activities ........................................................................................... 96

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Lesson 5 E-Mail ..................................................................................97 How Does E-Mail Work? .................................................................. 97 Reading an E-Mail Address ............................................................... 98 E-Mail Protocols ............................................................................... 99 SMTP ........................................................................................ 100 Uuencode ......................................................................... 100 MIME ................................................................................ 100 S/MIME ............................................................................. 102 POP ................................................................................... 103 IMAP4 ............................................................................... 103 Mail Server Configuration .............................................................. 103 Store-and-Forward Mail Systems .................................................... 104 Activities ......................................................................................... 106

Lesson 6 Network Management ......................................................109 Network Management Concepts ................................................... 110 Types of Managed Nodes/Devices ................................................. 111 Network Management Model ........................................................ 113 Managed Nodes/Devices ......................................................... 113 SNMP Agents ........................................................................... 114 NMS ......................................................................................... 114 Network Management Protocol .............................................. 114 Network Management Modes ........................................................ 116 Passive Management ............................................................... 117 Active Management ................................................................ 120 Exception Management .......................................................... 120 RMON ............................................................................................. 121 How RMON Works .................................................................. 121 RMON Extensions to SNMP .................................................... 122 RMON2 .................................................................................... 123 Activities ......................................................................................... 125

Lesson 7 Other Applications .............................................................128 NFS ................................................................................................. 128 Rlogin ............................................................................................. 129 X-Windows ..................................................................................... 130 DNS ................................................................................................ 130 TFTP ................................................................................................ 131 NNTP .............................................................................................. 134 DHCP/BOOTP ................................................................................ 136 Obtaining an Address From a DHCP Server ........................... 137 WINS ....................................................................................... 138

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Contents LMHosts .................................................................................. 139 Activities ......................................................................................... 140

Summary ...........................................................................142 Quiz ..................................................................................144 Unit 3 TCP/IP Addressing and Subnets ......................................149 Lesson 1 Number Conversion ..........................................................153 Decimal to Binary Conversion ....................................................... 153 Divide by Two ......................................................................... 154 Binary to Decimal Conversion ....................................................... 155 Decimal to Binary Conversion Related to IP Addressing .............. 156 Activities ......................................................................................... 159

Lesson 2 Subnetting Fundamentals ..................................................162 The Value of Subnetting ................................................................ 162 The IP Address Crisis ............................................................... 163 Why Multiple Network Segments? ......................................... 163 Interconnection of TCP/IP Networks ............................................. 163 The Network Mask ......................................................................... 165 Creating Subnets ............................................................................ 167 Recapping What We Have Learned Thus Far ................................ 169 Maximum Usable Subnets and Hosts ............................................ 170 IP Prefixes ................................................................................ 173 Determining Subnet Requirements ............................................... 176 IP Broadcast Addresses ................................................................... 177 Limited Broadcast ........................................................................... 178 Directed Broadcast ......................................................................... 178 Activities ......................................................................................... 179

Lesson 3 Subnetting Class C Networks .............................................186 Determining Address Ranges ......................................................... 186 Network Address Ranges ......................................................... 187 Subnetwork Address Ranges .................................................... 188 Building the Range .................................................................. 190 Sample Problem #1 ........................................................................ 201 Sample Problem #2 ........................................................................ 203 Activities ......................................................................................... 205

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Lesson 4 Subnetting Class B Networks .............................................210 Building the Address Range ........................................................... 211 Sample Problem #1 ........................................................................ 220 Sample Problem #2 ........................................................................ 224 Activities ......................................................................................... 226

Lesson 5 Subnetting Class A Networks .............................................230 Building the Address Range ........................................................... 230 Sample Problem #1 ........................................................................ 240 Sample Problem #2 ........................................................................ 242 Activities ......................................................................................... 245

Lesson 6 CIDR ..................................................................................249 The Need for CIDR ......................................................................... 250 Large Routing Tables ............................................................... 253 The Proposed Solution ............................................................ 253 How CIDR Works ........................................................................... 254 Reduction of Routing Table Entries ........................................ 255 Creating a Supernet .......................................................... 256 Contiguous Address Space ...................................................... 257 Sample Problem #1 ........................................................................ 257 Sample Problem #2 ........................................................................ 258 Sample Problem #3 ........................................................................ 259 Activities ......................................................................................... 262

Summary ...........................................................................264 Quiz ..................................................................................266 Unit 4 TCP/IP Protocols ..............................................................273 Lesson 1 IP .......................................................................................276 Overview of IP ................................................................................ 276 IP Header Format and Field Descriptions ...................................... 278 ToS .................................................................................................. 281 Precedence Bits ........................................................................ 281 D-T-R-C Bits ............................................................................. 282 Fragmentation ................................................................................ 282 MTU ......................................................................................... 282 Fields Controlling Fragmentation ........................................... 284 Fragmentation Example .......................................................... 284 TTL ................................................................................................. 286 Protocol .......................................................................................... 286 Addressing ...................................................................................... 287 Options ........................................................................................... 287 x

Contents Record Route Option ............................................................... 288 Source Route Option ............................................................... 288 Time Stamp Option ................................................................. 288 IP Packet Encapsulation ................................................................. 288 Activities ......................................................................................... 290

Lesson 2 Address Resolution .............................................................294 ARP ................................................................................................. 294 ARP's Operation ....................................................................... 294 ARP Request ...................................................................... 295 ARP Response ................................................................... 298 ARP Features ..................................................................... 298 Proxy ARP ......................................................................... 300 Frame Encapsulation ...................................................................... 300 RARP ............................................................................................... 301 Operation ................................................................................ 302 RARP Request ................................................................... 302 RARP Response ................................................................. 303 Activities ......................................................................................... 304

Lesson 3 UDP ...................................................................................306 UDP Service .................................................................................... 306 Demultiplexing Based on Port Number ......................................... 308 UDP Port Numbers ......................................................................... 310 Frame Encapsulation ...................................................................... 311 Activities ......................................................................................... 312

Lesson 4 TCP and Connection Establishment ...................................315 TCP Features ................................................................................... 315 TCP Interfaces ................................................................................ 317 The TCP Header ............................................................................. 317 Fundamental Operation ................................................................. 319 Basic Data Transfer .................................................................. 319 Reliability ................................................................................ 320 Flow Control ........................................................................... 320 Multiplexing ............................................................................ 320 Connections ............................................................................ 321 Sequence Numbers ......................................................................... 321 Ports ................................................................................................ 323 Sockets ............................................................................................ 325 Connection Establishment ............................................................ 327 Active Open ............................................................................. 327 Passive Open ........................................................................... 328 Activities ......................................................................................... 329

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Lesson 5 TCP and Data Transmission ...............................................333 Connection Establishment Functions ........................................... 333 Three-Way Handshake ............................................................ 334 Handshake #1 ................................................................... 334 Handshake #2 ................................................................... 335 Handshake #3 ................................................................... 336 Data Transmission .......................................................................... 337 Sequence Numbers .................................................................. 337 Segments ................................................................................. 337 Push and Urgent Flags ............................................................. 338 ACK and Retransmission ......................................................... 339 Smooth Round-Trip Time ....................................................... 341 Data Reception ........................................................................ 341 Window Management ................................................................... 342 Efficient Transmission ............................................................. 343 Flow Control .................................................................................. 344 Variable-Sized Windows .......................................................... 344 Zero Receive Window ............................................................. 345 Connection Termination ............................................................... 345 Side Initiating Disconnection Request .................................... 346 Side Responding to Disconnection Request ........................... 346 Connection Reset—Crash Recovery ............................................... 346 Frame Encapsulations .................................................................... 347 Activities ......................................................................................... 348

Lesson 6 Moving Information Across a TCP/IP Network ...................352 Information Transfer ...................................................................... 352 Primary Functions of Each Layer ................................................... 353 Addressing in Computer Networks ................................................ 353 Physical Addresses ................................................................... 354 Logical Addresses ..................................................................... 354 Obtaining Logical Addresses .......................................................... 355 Obtaining Physical Addresses ........................................................ 356 Establishing a Connection Between Applications ......................... 357 Transferring Information ............................................................... 357 Terminating the Connection ......................................................... 357 Activities ......................................................................................... 358

Summary ...........................................................................360 Quiz ..................................................................................361

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Unit 5 TCP/IP Services ................................................................367 Lesson 1 DNS ..................................................................................372 Overview of DNS ............................................................................ 372 Hierarchical Structure .................................................................... 373 The Hosts File .......................................................................... 374 The DNS Hierarchy ................................................................. 375 TLDs ................................................................................. 375 Second-Level Subdomains ................................................ 376 Consistent Naming Scheme ........................................................... 378 Domain Names ........................................................................ 378 Defining Uniqueness ............................................................... 378 DNS Tree Structure ......................................................................... 380 Domain Name Syntax ............................................................. 381 Authority Over Domains ............................................................... 382 Domain Administrators .......................................................... 382 Zones .............................................................................................. 382 RRs ........................................................................................... 384 RR Format ......................................................................... 384 Name Servers .................................................................................. 386 Authoritative Zone Information .................................................... 386 Master Files ..................................................................................... 387 Cached Data ................................................................................... 389 Resolvers ......................................................................................... 390 Querying the Name Database ................................................. 390 Activities ......................................................................................... 392

Lesson 2 ICMP .................................................................................394 ICMP and the OSI Model ............................................................... 394 Encapsulation ................................................................................. 396 Header Format ................................................................................ 397 Message Types ................................................................................ 399 Destination Unreachable (3) ................................................... 399 Time Exceeded (11) ................................................................. 399 Parameter Problem (12) .......................................................... 399 Source Quench (4) ................................................................... 400 Redirect (5) .............................................................................. 400 Echo Request (8) and Echo Reply (0) ...................................... 401 Timestamp Request (13) and Timestamp Reply (14) .............. 401 Information Request (15) and Information Reply (16) .......... 401 Address Mask Request (17) and Address Mask Reply (18) ...... 401 Activities ......................................................................................... 402

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Lesson 3 IGMP .................................................................................404 IP Multicasting ............................................................................... 404 Multicast Addressing ............................................................... 405 IP Multicast Addresses and Groups ......................................... 406 Mapping IP Multicast Addresses to Physical Multicast Addresses . 407 IGMP Message Format .................................................................... 408 Header Format ......................................................................... 409 Operations ............................................................................... 409 Encapsulation .......................................................................... 410 Activities ......................................................................................... 411

Lesson 4 BOOTP ..............................................................................412 BOOTP ............................................................................................ 412 BOOTP Operation .......................................................................... 415 Client BOOTREQUEST Message .............................................. 415 Server BOOTREPLY Message ................................................... 417 Client BOOTREPLY Message Receipt ...................................... 420 Client BOOTREQUEST Retransmission .................................. 420 The BOOTP Relay Agent ................................................................ 421 BOOTP Relay Agent Operations .............................................. 421 Relay Agent BOOTREQUEST Processing .......................... 421 Relay Agent BOOTREPLY Processing ............................... 423 Activities ......................................................................................... 425

Lesson 5 DHCP ................................................................................427 DHCP .............................................................................................. 428 DHCP Address Allocation Mechanisms .................................. 428 DHCP Message Format ................................................................... 429 DHCP Services ................................................................................ 431 DHCP Operation ............................................................................ 432 How DHCP Clients Obtain Configuration Information ........ 433 Client Initialization—DHCPDISCOVER Message ................... 434 DHCP Server—DHCPOFFER Message ..................................... 437 DHCP Client—DHCPREQUEST Message ................................ 439 DHCP Server—DHCPACK ....................................................... 440 DHCP Client—DHCPACK Receipt .......................................... 441 DHCP Server—DHCPNAK Message ........................................ 441 DHCP Client—DHCPNAK Message ........................................ 441 Initializing With an Existing Address ..................................... 441 DHCP Client Lease Renewal .......................................................... 442 DHCP Relay Agents ........................................................................ 443 DHCP Client—DHCPRELEASE Message ........................................ 444 Activities ......................................................................................... 447

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Contents

Lesson 6 NAT ...................................................................................451 NAT ................................................................................................ 451 What Is Address Reuse? ........................................................... 451 A NAT Overview ............................................................................. 453 NAT Address Spaces ................................................................. 453 IP Address Translation ............................................................. 454 Static Address Translation .............................................................. 454 Dynamic Address Translation ........................................................ 455 Enhanced Network Security .................................................... 455 Masquerading/NAPT ...................................................................... 457 NAPT—Even More Security ..................................................... 461 Activities ......................................................................................... 462

Lesson 7 IPv6 ...................................................................................465 IP Next Generation ........................................................................ 465 Expanded Addresses ................................................................ 466 Multimedia Ready ................................................................... 466 Priority Field ..................................................................... 466 Flow Label Field ................................................................ 467 Multicast Support .................................................................... 468 Bandwidth Reservations .......................................................... 468 Packet Prioritizing ................................................................... 468 Jumbograms ............................................................................ 468 Plug and Play Address Discovery ............................................ 468 Network Information Discovery ............................................. 468 Automated Address Changes .................................................. 468 Support for Mobile Hosts ........................................................ 468 Dead Neighbor Detection ....................................................... 469 Increased Efficiency ........................................................................ 469 Simplified Headers .................................................................. 469 Packet Size Optimization ................................................. 469 Less Load on Hosts ........................................................... 469 Route Aggregation ............................................................ 469 Added Flexibility ..................................................................... 469 Control Over Options Handling ...................................... 470 Control Over Routing ...................................................... 470 Anycast Addressing .......................................................... 470 Configurability of Features ..................................................... 470 IPv4 Compatibility .................................................................. 470 IPv4 Address Translation .................................................. 470 Dual Protocol Stacks ......................................................... 470 IPv6 Tunneled Over IPv4 ................................................. 470

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Introduction to TCP/IP Security Infrastructure .................................................................... 470 Encryption ............................................................................... 471 Authentication ........................................................................ 471 IPv6 Header Format ........................................................................ 471 Activities ......................................................................................... 473

Summary ...........................................................................474 Quiz ..................................................................................476 Unit 6 Routing TCP/IP ................................................................483 Lesson 1 IP Routing ..........................................................................488 Overview of Internet Architecture ................................................. 488 Direct Routing ................................................................................ 490 Indirect Routing ............................................................................. 491 Routing Tables ................................................................................ 492 Building the Routing Table ..................................................... 492 Sample Network Routing Table .............................................. 494 Model of Operation ........................................................................ 496 Host A ...................................................................................... 497 Packet on Network 128.1.0.0 .................................................. 497 Packet on Network 128.2.0.0 .................................................. 498 Packet on Network 128.3.0.0 .................................................. 498 Packet on Network 128.4.0.0 .................................................. 499 Host B ...................................................................................... 500 Static Routing ................................................................................. 500 Default Routes ................................................................................ 502 Dynamic Routing ........................................................................... 503 ADs ................................................................................................. 504 Activity ........................................................................................... 505

Lesson 2 How Routers Share Routing Information ............................507 Routing Information ...................................................................... 508 ASs .................................................................................................. 509 Gateway Protocols .......................................................................... 511 IGPs ......................................................................................... 511 EGPs ......................................................................................... 511 Types of Dynamic Routing Protocols ............................................ 512 DVAs ........................................................................................ 513 DVA Basic Operation ........................................................ 513 DVA Advantages ............................................................... 513 DVA Disadvantages .......................................................... 513 LSAs ......................................................................................... 514 LSA Basic Operation ......................................................... 514 LSA Advantages ................................................................ 514 LSA Disadvantages ........................................................... 514 xvi

Contents Multipath Routing ......................................................................... 515 Router-Based Network Architectures ............................................. 516 Flat Router Networks ............................................................... 516 Flat Networks Are Simple ................................................. 516 Flat Networks Are Less Efficient ....................................... 516 Hierarchical Networks ............................................................. 517 Hierarchical Networks Control Routing Table Updates .. 517 Hierarchical Networks Can Eliminate Routing Loops ..... 518 Simpler Hierarchies Using LSAs ....................................... 518 Activities ......................................................................................... 519

Lesson 3 RIP .....................................................................................522 Overview of RIP .............................................................................. 522 RIP Updates ............................................................................. 523 RIP Stability Features ...................................................................... 523 Hop-Count Limit ..................................................................... 524 Holddowns .............................................................................. 524 Split Horizons .......................................................................... 526 Poison Reverse Updates ........................................................... 527 RIP Timers ............................................................................... 528 Novell RIP ....................................................................................... 528 RIPv2 .............................................................................................. 530 Route Tag ................................................................................. 531 Subnet Mask ............................................................................ 532 Next Hop ................................................................................. 532 Metric ...................................................................................... 532 Authentication ........................................................................ 532 Activities ......................................................................................... 534

Lesson 4 IGRP ..................................................................................540 Overview of IGRP ........................................................................... 540 IGRP Updates .......................................................................... 541 IGRP Stability Features ................................................................... 542 Holddowns .............................................................................. 542 Split Horizons .......................................................................... 543 Poison Reverse Updates ........................................................... 543 Flash Updates .......................................................................... 543 IGRP Timers ............................................................................. 543 IGRP Metrics ................................................................................... 544 Activities ......................................................................................... 545

Lesson 5 OSPF .................................................................................547 Review of Link-State Routing ......................................................... 547 RIP Limitations ............................................................................... 548 OSPF Solution ................................................................................. 549 Routing Areas ................................................................................. 550 xvii

Introduction to TCP/IP Area Routing Components ............................................................ 550 ABR .......................................................................................... 551 Backbone Area ......................................................................... 552 Virtual Links ............................................................................ 553 ASBR ........................................................................................ 553 Stub Areas ................................................................................ 554 Neighbors and Adjacencies ............................................................ 554 DR and BDR ............................................................................. 554 Forming Adjacencies ...................................................................... 555 Phase 1: Finding Neighbor Routers ......................................... 555 Phase 2: Synchronizing Link-State Databases ......................... 556 Phase 3: Maintaining Database Synchronization ................... 556 Link-State Advertisement Types .............................................. 557 ToS Routing .................................................................................... 559 Activities ......................................................................................... 561

Lesson 6 Advanced Routing .............................................................563 IGP and EGP ................................................................................... 563 EGP ................................................................................................. 565 BGP-4 .............................................................................................. 566 BGP in Practice ........................................................................ 567 BGP-4 Message Header Format ............................................... 568 BGP-4 Open Packet Format ..................................................... 569 Advanced Routing Functions ......................................................... 570 Least-Cost Routing .................................................................. 570 Load Splitting .......................................................................... 571 CoS Routing ............................................................................ 571 ToS/QoS Routing ..................................................................... 571 Policy-Based Routing ............................................................... 572 Activities ......................................................................................... 573

Summary ...........................................................................575 Quiz ..................................................................................577 Unit 7 How TCP/IP Applications Work .......................................583 Lesson 1 Web Browser and Web Server Step-by-Step .......................589 Server Waits for a Client Request ................................................... 590 Client Resolves Server IP Address ................................................... 591 Client TCP Sends a Connection Request to Web Server TCP Process ...................................................... 596 The Server TCP Process Responds to the Client TCP Process ........ 600 Client Acknowledges the Server TCP Connection Request ........... 603 Client Sends HTTP Request to Web Server ............................. 604 The Server Processes the Web Page Request .................................. 607 Activity ........................................................................................... 612 xviii

Contents

Lesson 2 Telnet ................................................................................616 Remote Terminal Access ................................................................ 617 VTP .......................................................................................... 619 Telnet Overview ...................................................................... 620 Client Telnet and Server Telnet ....................................... 620 Telnet NVT .............................................................................. 621 Negotiated Options ................................................................. 622 Default NVT ............................................................................ 622 Telnet Data Transfer ................................................................ 623 Transmission of Control Functions ........................................ 624 Out-of-Band Signaling (Telnet Synch) .................................... 625 Urgent Flag and Data Mark Command ........................... 625 Options Negotiations .............................................................. 626 Single Command Options Negotiation Format ............... 627 Subnegotiations ................................................................ 628 Extended Options List ............................................................. 629 Telnet Options ................................................................. 629 Activities ......................................................................................... 631

Lesson 3 FTP ....................................................................................633 Overview of FTP ............................................................................. 633 File Transfer Issues ................................................................... 635 Data Type ......................................................................... 635 File Structure .................................................................... 636 Transmission Mode .......................................................... 637 Sample File Transfer ....................................................................... 638 User and Server Processes ............................................................... 639 DTP .......................................................................................... 639 FTP Command Structure ......................................................... 640 Sample FTP Implementation ................................................... 643 Start FTP ........................................................................... 643 Transfer Files .................................................................... 643 Close Connection ............................................................. 643 Activities ......................................................................................... 644

Lesson 4 SMTP .................................................................................645 SMTP Commands ........................................................................... 645 Overview of SMTP .......................................................................... 646 SMTP Mail Process .......................................................................... 647 Sender SMTP ............................................................................ 647 Receiver SMTP ......................................................................... 648 Mail Addresses ................................................................................ 648 Two-Part Names ...................................................................... 648 SMTP Mail Transfer ................................................................. 648 Connection Establishment .............................................. 648

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Introduction to TCP/IP Data Transfer .................................................................... 649 Connection Closure ......................................................... 652 Activities ......................................................................................... 653

Lesson 5 Network Management ......................................................655 SNMP and OSI Model ..................................................................... 655 Basic Operation ....................................................................... 656 SNMP Architecture ......................................................................... 656 SNMP Proxy Agents ................................................................. 658 SNMP Management Station .................................................... 659 MIB ................................................................................................. 661 Management Objects .............................................................. 661 MIB Object Definitions ........................................................... 661 Systems Group (1) ................................................................... 662 Interface Group (2) .................................................................. 662 Address Translation Group (3) ................................................ 662 IP Group (4) ............................................................................. 662 ICMP Group (5) ....................................................................... 662 TCP Group (6) ......................................................................... 662 UDP Group (7) ........................................................................ 663 MIB Name Tree and Internet Subtrees ........................................... 663 Directory .................................................................................. 664 Management ........................................................................... 664 Managed Objects ..................................................................... 665 Experimental ........................................................................... 666 Private ...................................................................................... 666 Operations and PDUs ..................................................................... 667 PDU Types ............................................................................... 667 Actions Supported by SNMP Protocols .......................................... 668 Agent Actions .......................................................................... 668 Network Management Station Actions ................................... 669 SNMP Encoding ...................................................................... 669 ASN.1 ................................................................................ 669 Protocol Layering ............................................................. 670 Message Format .............................................................................. 671 Version Number ...................................................................... 671 Community String .................................................................. 671 PDU ......................................................................................... 671 Activities ......................................................................................... 673

Lesson 6 H.323 Standard for Packet Multimedia ..............................676 Overview of the H.323 Standard .................................................... 676 Version 1: Videophone ........................................................... 677 Version 2: Packet-Based Multimedia ....................................... 677 Version 3: Connection Reuse .................................................. 677 Version 4: Added Scalability ................................................... 677

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Contents Other Standards of the H.32x Family ............................................ 678 Components of an H.323 Network ......................................... 678 Terminals .......................................................................... 678 MCUs ................................................................................ 679 Gateways .......................................................................... 679 Gatekeepers ...................................................................... 680 H.323 Protocols ....................................................................... 681 Audio Codecs ................................................................... 682 Video Codecs .................................................................... 682 RTP ................................................................................... 682 RTCP ................................................................................. 684 RAS: H.225 ........................................................................ 684 Call Signaling: H.225 ....................................................... 684 Control Signaling: H.245 ................................................. 684 Document Conferencing: T.120 Series ............................ 684 Network Infrastructure Requirements ........................................... 685 Activities ......................................................................................... 686

Summary ...........................................................................689 Quiz ..................................................................................690 Unit 8 Troubleshooting a TCP/IP Network ................................697 Lesson 1 Troubleshooting Principles .................................................699 Troubleshooting Steps .................................................................... 699 Identify the Exact Issue ........................................................... 700 Re-Create the Problem ............................................................ 700 Isolate the Cause ..................................................................... 700 Formulate and Implement a Correction ................................. 700 Test the Solution ..................................................................... 701 Document the Problem and Solution and Provide Feedback . 701 Tools Used for Troubleshooting a TCP/IP Network ....................... 701 Activities ......................................................................................... 702

Lesson 2 Winipcfg ............................................................................704 TCP/IP Applications and Tools ...................................................... 704 Activities ......................................................................................... 708

Lesson 3 Ping ...................................................................................709 Ping Operation ............................................................................... 710 Activities ......................................................................................... 714

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Lesson 4 Tracert ...............................................................................715 How Tracert Works ........................................................................ 715 Activities ......................................................................................... 719

Lesson 5 Nbtstat and Netstat ...........................................................721 Nbtstat ............................................................................................ 722 Netstat ............................................................................................ 725 Activity ........................................................................................... 726

Lesson 6 ARP ...................................................................................727 ARP Operation ................................................................................ 727 Activity ........................................................................................... 731

Lesson 7 A Troubleshooting Problem ...............................................732 The Problem ................................................................................... 732 Identify the Exact Issue .................................................................. 732 Re-Create the Problem ................................................................... 733 Isolate the Cause ............................................................................ 734 Phase 1—Internal Communications ....................................... 735 Phase 2—ISP Communications ............................................... 737 Phase 3—Web Host Firm Communications ........................... 737 Tallying the Results ................................................................. 738 Isolating the Cause .................................................................. 738 Formulate and Implement the Solution ........................................ 740 Test the Solution ............................................................................ 740 Document the Problem and Solution and Obtain Feedback ........ 740 Tools Used in Resolving This Problem ........................................... 741 Activities ......................................................................................... 742

Summary ...........................................................................746 Quiz ..................................................................................747 Course Quiz ......................................................................753 Glossary ............................................................................765 Index ................................................................................783

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