THE TCP/IP GUIDE by Charles M. Kozierok SECTION I TCP/IP OVERVIEW AND BACKGROUND INFORMATION PART I-1 NETWORKING FUNDAMENTALS 1 NETWORKING INTRODUCTION, CHARACTERISTICS, AND TYPES 5 Introduction to Networking ................................................................................................ 6 What Is Networking? ................................................................................................. 6 The Advantages and Benefits of Networking ................................................................. 7 The Disadvantages and Costs of Networking ................................................................ 9 Fundamental Network Characteristics ............................................................................... 10 Networking Layers, Models, and Architectures ............................................................ 10 Protocols: What Are They, Anyway? .......................................................................... 11 Circuit-Switching and Packet-Switching Networks ........................................................ 13 Connection-Oriented and Connectionless Protocols ...................................................... 16 Messages: Packets, Frames, Datagrams, and Cells ............................................................. 17 Message Formatting: Headers, Payloads, and Footers ................................................. 19 Message Addressing and Transmission Methods: Unicast, Broadcast, and Multicast ........ 20 Network Structural Models and Client-Server and Peer-to-Peer Networking ............................ 23 Types and Sizes of Networks ........................................................................................... 26 Segments, Networks, Subnetworks, and Internetworks ........................................................ 27 The Internet, Intranets, and Extranets ................................................................................. 30 2 NETWORK PERFORMANCE ISSUES AND CONCEPTS 33 Putting Network Performance in Perspective ....................................................................... 34 Balancing Network Performance with Key Nonperformance Characteristics .......................... 35 Performance Measurements: Speed, Bandwidth, Throughput, and Latency ............................ 36 Speed .................................................................................................................... 36 Bandwidth .............................................................................................................. 37 Throughput ............................................................................................................. 37 Latency .................................................................................................................. 37 Summary of Performance Measurements .................................................................... 38 Understanding Performance Measurement Units ................................................................. 39 Bits and Bytes ......................................................................................................... 39 Baud ..................................................................................................................... 40 Theoretical and Real-World Throughput, and Factors Affecting Network Performance ............. 41 Normal Network Overhead ...................................................................................... 41 External Performance Limiters .................................................................................... 42 Network Configuration Problems ............................................................................... 42 Asymmetry ............................................................................................................. 43 Simplex, Full-Duplex, and Half-Duplex Operation ............................................................... 43 Simplex Operation .................................................................................................. 44 Half-Duplex Operation ............................................................................................. 44 Full-Duplex Operation .............................................................................................. 44 Quality of Service (QoS) ................................................................................................. 45
Transcript
T H E T C P / I P G U I D Eby Charles M. Kozierok
SECTION ITCP/IP OVERVIEW AND BACKGROUND INFORMATION
PART I-1NETWORKING FUNDAMENTALS
1NETWORKING INTRODUCTION, CHARACTERISTICS, AND TYPES 5
Introduction to Networking ................................................................................................6What Is Networking? .................................................................................................6The Advantages and Benefits of Networking .................................................................7The Disadvantages and Costs of Networking ................................................................9
Fundamental Network Characteristics ...............................................................................10Networking Layers, Models, and Architectures ............................................................10Protocols: What Are They, Anyway? ..........................................................................11Circuit-Switching and Packet-Switching Networks ........................................................13Connection-Oriented and Connectionless Protocols ......................................................16
Messages: Packets, Frames, Datagrams, and Cells .............................................................17Message Formatting: Headers, Payloads, and Footers .................................................19Message Addressing and Transmission Methods: Unicast, Broadcast, and Multicast ........20
Network Structural Models and Client-Server and Peer-to-Peer Networking ............................23Types and Sizes of Networks ...........................................................................................26Segments, Networks, Subnetworks, and Internetworks ........................................................27The Internet, Intranets, and Extranets .................................................................................30
2NETWORK PERFORMANCE ISSUES AND CONCEPTS 33
Putting Network Performance in Perspective .......................................................................34Balancing Network Performance with Key Nonperformance Characteristics ..........................35Performance Measurements: Speed, Bandwidth, Throughput, and Latency ............................36
Speed ....................................................................................................................36Bandwidth ..............................................................................................................37Throughput .............................................................................................................37Latency ..................................................................................................................37Summary of Performance Measurements ....................................................................38
Understanding Performance Measurement Units .................................................................39Bits and Bytes .........................................................................................................39Baud .....................................................................................................................40
Theoretical and Real-World Throughput, and Factors Affecting Network Performance .............41Normal Network Overhead ......................................................................................41External Performance Limiters ....................................................................................42Network Configuration Problems ...............................................................................42Asymmetry .............................................................................................................43
Quality of Service (QoS) .................................................................................................45
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3NETWORK STANDARDS AND STANDARDS ORGANIZATIONS 47
Proprietary, Open, and De Facto Standards ......................................................................48Proprietary Standards ..............................................................................................48Open Standards .....................................................................................................49De Facto Standards .................................................................................................50
Networking Standards ....................................................................................................50International Networking Standards Organizations ............................................................51Networking Industry Groups ............................................................................................53Internet Standards Organizations (ISOC, IAB, IESG, IETF, IRSG, and IRTF) ............................54Internet Registration Authorities and Registries
(IANA, ICANN, APNIC, ARIN, LACNIC, and RIPE NCC) ......................................57Internet Centralized Registration Authorities ................................................................57Modern Hierarchy of Registration Authorities ..............................................................58
Internet Standards and the Request for Comment (RFC) Process ............................................59RFC Categories .......................................................................................................60The Internet Standardization Process ..........................................................................60
4A REVIEW OF DATA REPRESENTATION ANDTHE MATHEMATICS OF COMPUTING 63
Binary Information and Representation: Bits, Bytes, Nibbles, Octets, and Characters ..............64Binary Information ...................................................................................................64Binary Information Representation and Groups ...........................................................65Byte Versus Octet ....................................................................................................66
Decimal, Binary, Octal, and Hexadecimal Numbers ...........................................................67Binary Numbers and Their Decimal Equivalents ...........................................................67Making Binary Numbers Easier to Use by Grouping Bits ..............................................68Octal Numbers .......................................................................................................68Hexadecimal Numbers ............................................................................................69
Decimal, Binary, Octal, and Hexadecimal Number Conversion ...........................................70Binary, Octal, and Hexadecimal Conversions .............................................................70Conversion from Binary, Octal, or Hexadecimal to Decimal .........................................71Conversion from Decimal to Binary, Octal or Hexadecimal ..........................................72
Binary, Octal, and Hexadecimal Arithmetic .......................................................................73Binary Arithmetic .....................................................................................................74Octal and Hexadecimal Arithmetic ............................................................................74
Bit Masking (Setting, Clearing, and Inverting) Using Boolean Logical Functions ......................77Setting Groups of Bits with OR ..................................................................................78Clearing Bits with AND ............................................................................................78Inverting Bits with XOR .............................................................................................79
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PART I-2THE OPEN SYSTEM INTERCONNECTION (OSI)REFERENCE MODEL
5GENERAL OSI REFERENCE MODEL ISSUES AND CONCEPTS 83
History of the OSI Reference Model ..................................................................................84General Reference Model Issues ......................................................................................85
The Benefits of Networking Models ...........................................................................85Why Understanding the OSI Reference Model Is Important to You .................................86How to Use the OSI Reference Model ........................................................................87Other Network Architectures and Protocol Stacks ........................................................88
Key OSI Reference Model Concepts .................................................................................89OSI Reference Model Networking Layers, Sublayers, and Layer Groupings ....................89“N” Notation and Other OSI Model Layer Terminology ...............................................91Interfaces: Vertical (Adjacent Layer) Communication ....................................................93Protocols: Horizontal (Corresponding Layer) Communication ........................................95Data Encapsulation, Protocol Data Units (PDUs), and Service Data Units (SDUs) ..............97Indirect Device Connection and Message Routing ..................................................... 100
Understanding the OSI Model: An Analogy ..................................................................... 115Remembering the OSI Model Layers: Some Mnemonics .................................................... 118Summarizing the OSI Model Layers: A Summary Chart ..................................................... 119
PART I-3TCP/IP PROTOCOL SUITE AND ARCHITECTURE
8TCP/IP PROTOCOL SUITE AND ARCHITECTURE 123
TCP/IP Overview and History ........................................................................................ 124TCP/IP History and Development ............................................................................. 124Important Factors in the Success of TCP/IP ................................................................ 125
TCP/IP Services ........................................................................................................... 127The TCP/IP Client/Server Structural Model ......................................................................127
Hardware and Software Roles ................................................................................ 129Transactional Roles ................................................................................................ 129
TCP/IP Architecture and the TCP/IP Model ......................................................................130
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PART II -1TCP/IP NETWORK INTERFACE LAYER PROTOCOLS
9TCP/IP SERIAL LINE INTERNET PROTOCOL (SLIP)AND POINT-TO-POINT PROTOCOL PPP OVERVIEWAND FUNDAMENTALS 141
SLIP versus PPP ............................................................................................................. 142Serial Line Internet Protocol (SLIP) ................................................................................... 143
SLIP Data Framing Method and General Operation ................................................... 143Problems and Limitations of SLIP .............................................................................. 144
Point-to-Point Protocol (PPP) Overview and Fundamentals ................................................... 146Development and Standardization ........................................................................... 146Function and Architecture ....................................................................................... 147Advantages and Benefits ........................................................................................ 147PPP Main Components ...........................................................................................148PPP Functional Groups ...........................................................................................149General Operation ................................................................................................ 149PPP Link Setup and Phases ...................................................................................... 150PPP Standards .......................................................................................................153
10PPP CORE PROTOCOLS: LINK CONTROL, NETWORKCONTROL, AND AUTHENTICATION 157
Link Control Protocol (LCP) .............................................................................................157LCP Packets .......................................................................................................... 158LCP Link Configuration ...........................................................................................159LCP Link Maintenance ............................................................................................161LCP Link Termination .............................................................................................. 161Other LCP Messages .............................................................................................. 161
The Network Control Protocols (IPCP, IPXCP, NBFCP, and Others) .....................................161Operation of NCPs ................................................................................................ 162The Internet Protocol Control Protocol (IPCP): An Example NCP ................................... 164
PPP Authentication Protocols: PAP and CHAP ................................................................... 164PAP ..................................................................................................................... 164CHAP ..................................................................................................................165
11PPP FEATURE PROTOCOLS 169
PPP Link Quality Monitoring and Reporting (LQM, LQR) .................................................... 170LQR Setup ............................................................................................................ 170
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Using Link Quality Reports ...................................................................................... 171PPP Compression Control Protocol (CCP) and Compression Algorithms ............................... 171
CCP Operation: Compression Setup ........................................................................ 172CCP Configuration Options and Compression Algorithms .......................................... 173Compression Algorithm Operation: Compressing and Decompressing Data .................173
PPP Encryption Control Protocol (ECP) and Encryption Algorithms ....................................... 174ECP Operation: Encryption Setup ............................................................................ 175ECP Configuration Options and Encryption Algorithms .............................................. 175Encryption Algorithm Operation: Encrypting and Decrypting Data ............................... 176
PPP Bandwidth Allocation Protocol (BAP) and Bandwidth Allocation Control Protocol (BACP) . 180BACP Operation: Configuring the Use of BAP ...........................................................181BAP Operation: Adding and Removing Links ............................................................181
12PPP PROTOCOL FRAME FORMATS 183
PPP General Frame Format ............................................................................................184Protocol Field Ranges .............................................................................................185Protocol Field Values .............................................................................................186PPP Field Compression ...........................................................................................187
PPP General Control Protocol Frame Format and Option Format ........................................ 188PPP Control Messages and Code Values .................................................................. 189PPP Control Message Option Format .......................................................................190Summary of PPP Control Message Formatting ...........................................................192
PPP Link Control Protocol (LCP) Frame Formats ................................................................. 192PAP and CHAP Frame Formats ...................................................................................... 194
PPP PAP Control Frame Formats .............................................................................. 194PPP CHAP Control Frame Formats ........................................................................... 196
PPP Multilink Protocol (MP) Frame Format ........................................................................ 197PPP MP Frame Fragmentation Process ......................................................................198PPP MP Fragment Frame Format .............................................................................. 198PPP MP Fragmentation Demonstration ......................................................................200
PART II -2TCP/IP NETWORK INTERFACE/INTERNET LAYER CONNECTION PRO TOCOLS
13ADDRESS RESOLUTION AND THE TCP/IP ADDRESSRESOLUTION PROTOCOL (ARP) 205
Address Resolution Concepts and Issues .......................................................................... 206The Need for Address Resolution ............................................................................. 206Address Resolution Through Direct Mapping ............................................................. 208Dynamic Address Resolution ................................................................................... 211
TCP/IP Address Resolution Protocol (ARP) ........................................................................ 214ARP Address Specification and General Operation ................................................... 215ARP Message Format .............................................................................................218ARP Caching ........................................................................................................ 220
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Proxy ARP ............................................................................................................ 223TCP/IP Address Resolution for IP Multicast Addresses ....................................................... 225TCP/IP Address Resolution for IP Version 6 ......................................................................226
14REVERSE ADDRESS RESOLUTION AND THE TCP/IPREVERSE ADDRESS RESOLUTION PROTOCOL (RARP) 229
The Reverse Address Resolution Protocol (RARP) ............................................................... 230RARP General Operation .............................................................................................. 231Limitations of RARP .......................................................................................................232
PART II -3INTERNET PROTOCOL VERSION 4 ( IP/IPV4)
15INTERNET PROTOCOL VERSIONS: CONCEPTS AND OVERVIEW 237
IP Overview and Key Operational Characteristics ............................................................238IP Functions .................................................................................................................240IP History, Standards, Versions, and Closely Related Protocols ........................................... 241
IP Versions and Version Numbers ............................................................................ 241IP-Related Protocols ................................................................................................ 242
16IPV4 ADDRESSING CONCEPTS AND ISSUES 243
IP Addressing Overview and Fundamentals ..................................................................... 244Number of IP Addresses Per Device ......................................................................... 245Address Uniqueness and Network Specificity ............................................................245Contrasting IP Addresses and Data Link Layer Addresses ........................................... 246Private and Public IP Network Addresses .................................................................. 246IP Address Configuration and Addressing Types ....................................................... 246
IP Address Size, Address Space, and Notation ................................................................ 247IP Address Size and Binary Notation .......................................................................247IP Address Dotted Decimal Notation ........................................................................ 247IP Address Space .................................................................................................. 248
IP Basic Address Structure and Main Components ............................................................249Network ID and Host ID ......................................................................................... 249Location of the Division Between Network ID and Host ID ........................................... 250
IP Addressing Categories and IP Address Adjuncts ...........................................................251Conventional (Classful) Addressing .......................................................................... 252Subnetted Classful Addressing ................................................................................ 252Classless Addressing .............................................................................................252Subnet Mask and Default Gateway ......................................................................... 253
Number of IP Addresses and Multihoming .......................................................................253IP Address Management and Assignment Methods and Authorities .................................... 255
17CLASSFUL (CONVENTIONAL) ADDRESSING 257
IP Classful Addressing Overview and Address Classes ...................................................... 258IP Address Classes ................................................................................................ 258
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Rationale for Classful Addressing ............................................................................ 259IP Classful Addressing Network and Host Identification and Address Ranges ....................... 260
Classful Addressing Class Determination Algorithm ................................................... 260Determining Address Class from the First Octet Bit Pattern .......................................... 262
IP Address Class A, B, and C Network and Host Capacities .............................................. 264IP Addresses with Special Meanings ............................................................................... 265IP Reserved, Private, and Loopback Addresses ................................................................. 267
IP Multicast Addressing ................................................................................................. 270Multicast Address Types and Ranges ......................................................................270Well-Known Multicast Addresses ............................................................................. 271
Problems with Classful IP Addressing .............................................................................. 271
18IP SUBNET ADDRESSING (SUBNETTING) CONCEPTS 275
IP Subnet Addressing Overview, Motivation, and Advantages ........................................... 276IP Subnetting: Three-Level Hierarchical IP Subnet Addressing ............................................ 278IP Subnet Masks, Notation, and Subnet Calculations ........................................................ 279
Function of the Subnet Mask ................................................................................... 279Subnet Mask Notation ...........................................................................................280Applying the Subnet Mask: An Example ................................................................... 281Rationale for Subnet Mask Notation ........................................................................ 283
IP Default Subnet Masks for Address Classes A, B, and C .................................................283IP Custom Subnet Masks ............................................................................................... 285
Deciding How Many Subnet Bits to Use ................................................................... 285Determining the Custom Subnet Mask ......................................................................286Subtracting Two from the Number of Hosts per Subnet and
(Possibly) Subnets per Network ........................................................................ 288IP Subnet Identifiers, Subnet Addresses, and Host Addresses ............................................. 289
Subnet Identifiers ................................................................................................... 289Subnet Addresses .................................................................................................. 289Host Addresses Within Each Subnet ........................................................................ 290
IP Subnetting Summary Tables for Class A, Class B, and Class C Networks ......................... 291IP Variable Length Subnet Masking (VLSM) ......................................................................294
The Solution: Variable Length Subnet Masking .......................................................... 296Multiple-Level Subnetting Using VLSM ......................................................................296
19IP SUBNETTING PRACTICAL SUBNET DESIGN ANDADDRESS DETERMINATION EXAMPLE 299
Class C Subnetting Design Example ........................................................................ 302Class B Subnetting Design Example ......................................................................... 303
IP Subnetting Step 3: Determining the Custom Subnet Mask ............................................... 304Calculating the Custom Subnet Mask .......................................................................305Determining the Custom Subnet Mask Using Subnetting Tables ................................... 307
IP Subnetting Step 4: Determining Subnet Identifiers and Subnet Addresses ......................... 307Class C Subnet ID and Address Determination Example ............................................. 308
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Class B Subnet ID and Address Determination Example ............................................. 309Using Subnet Address Formulas to Calculate Subnet Addresses ................................... 311
IP Subnetting Step 5: Determining Host Addresses for Each Subnet .....................................312Class C Host Address Determination Example ...........................................................312Class B Host Address Determination Example ...........................................................315Shortcuts for Computing Host Addresses .................................................................. 315
IP Classless Addressing and Supernetting Overview ......................................................... 318The Main Problem with Classful Addressing .............................................................. 318The Solution: Eliminate Address Classes ................................................................... 319The Many Benefits of Classless Addressing and Routing ............................................. 319
IP Supernetting: CIDR Hierarchical Addressing and Notation ............................................. 321CIDR (Slash) Notation ............................................................................................321Supernetting: Subnetting the Internet ........................................................................ 322Common Aspects of Classful and Classless Addressing .............................................. 323
IP Classless Addressing Block Sizes and Classful Network Equivalents ................................ 324IP CIDR Addressing Example ......................................................................................... 326
First Level of Division .............................................................................................. 326Second Level of Division ......................................................................................... 327Third Level of Division ............................................................................................329
IP Datagram Encapsulation ............................................................................................332IP Datagram General Format ......................................................................................... 334
IP Datagram Time to Live (TTL) Field ......................................................................... 337IP Datagram Type of Service (TOS) Field .................................................................. 337
IP Datagram Options and Option Format ........................................................................ 338
IP Datagram Size, MTU, and Fragmentation Overview ..................................................... 342IP Datagram Size and the Underlying Network Frame Size ........................................ 342MTU and Datagram Fragmentation ......................................................................... 343Multiple-Stage Fragmentation ..................................................................................344Internet Minimum MTU: 576 Bytes ........................................................................... 345MTU Path Discovery .............................................................................................. 345
IP Message Fragmentation Process .................................................................................346The IP Fragmentation Process ..................................................................................346Fragmentation-Related IP Datagram Header Fields ..................................................... 348
IP Message Reassembly ............................................................................................... 349
23IP ROUTING AND MULTICASTING 353
IP Datagram Delivery .................................................................................................... 354
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Direct Datagram Delivery ....................................................................................... 355Indirect Datagram Delivery (Routing) ........................................................................ 355The Relationship Between Datagram Routing and Addressing .....................................356
IP Routing Concepts and the Process of Next-Hop Routing .................................................357IP Routes and Routing Tables ......................................................................................... 359IP Routing in a Subnet or Classless Addressing (CIDR) Environment .................................... 361IP Multicasting ............................................................................................................. 362
Multicast Addressing .............................................................................................363Multicast Group Management .................................................................................363Multicast Datagram Processing and Routing ............................................................. 363
PART II -4INTERNET PROTOCOL VERSION 6 ( IPV6)
24IPV6 OVERVIEW, CHANGES, AND TRANSITION 367
IPv6 Motivation and Overview ....................................................................................... 368IPv6 Standards ......................................................................................................368Design Goals of IPv6 .............................................................................................369
Major Changes and Additions in IPv6 ............................................................................ 370Transition from IPv4 to IPv6 ...........................................................................................372
IPv4 to IPv6 Transition: Differences of Opinion .......................................................... 372IPv4 to IPv6 Transition Methods ............................................................................... 373
25IPV6 ADDRESSING 375
IPv6 Addressing Overview: Addressing Model, Address Types, and Address Size ............... 376IPv6 Addressing Model Characteristics .................................................................... 376IPv6 Supported Address Types ................................................................................ 377IPv6 Address Size and Address Space ..................................................................... 378
IPv6 Address and Address Notation and Prefix Representation .......................................... 380IPv6 Address Hexadecimal Notation ........................................................................ 380Zero Compression in IPv6 Addresses .......................................................................381IPv6 Mixed Notation .............................................................................................. 382IPv6 Address Prefix Length Representation ................................................................ 383
IPv6 Address Space Allocation ...................................................................................... 383IPv6 Global Unicast Address Format ............................................................................... 385
Rationale for a Structured Unicast Address Block ....................................................... 385Generic Division of the Unicast Address Space ......................................................... 386IPv6 Implementation of the Unicast Address Space .................................................... 386Original Division of the Global Routing Prefix: Aggregators ....................................... 387A Sample Division of the Global Routing Prefix into Levels .......................................... 388
IPv6 Interface Identifiers and Physical Address Mapping ................................................... 390IPv6 Special Addresses: Reserved, Private, Unspecified, and Loopback .............................. 391
Special Address Types ...........................................................................................392IPv6 Private Addresses Type Scopes ........................................................................ 393
IPv6 Datagram Overview and General Structure .............................................................. 404IPv6 Datagram Main Header Format .............................................................................. 406
IPv6 Next Header Field .......................................................................................... 407Key Changes to the Main Header Between IPv4 and IPv6 .......................................... 408
IPv6 Datagram Extension Headers ..................................................................................409IPv6 Header Chaining Using the Next Header Field .................................................. 409Summary of IPv6 Extension Headers ........................................................................ 411IPv6 Routing Extension Header ................................................................................ 412IPv6 Fragment Extension Header ............................................................................. 413IPv6 Extension Header Order ..................................................................................413
IP NAT Overview ......................................................................................................... 428Advantages of IP NAT ...........................................................................................430Disadvantages of IP NAT ....................................................................................... 431
IP NAT Address Terminology ......................................................................................... 432IP NAT Static and Dynamic Address Mappings ................................................................ 435
Static Mappings .................................................................................................... 435Dynamic Mappings ............................................................................................... 435Choosing Between Static and Dynamic Mapping ...................................................... 435
IPsec Overview, History, and Standards .......................................................................... 452Overview of IPsec Services and Functions ................................................................. 453IPsec Standards ..................................................................................................... 453
IPsec General Operation, Components, and Protocols ...................................................... 454
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IPsec Core Protocols .............................................................................................. 455IPsec Support Components ..................................................................................... 455
IPsec Architectures and Implementation Methods .............................................................. 456Integrated Architecture ...........................................................................................457Bump in the Stack (BITS) Architecture .......................................................................457Bump in the Wire (BITW) Architecture ......................................................................458
IPsec Modes: Transport and Tunnel .................................................................................459Transport Mode .................................................................................................... 459Tunnel Mode ........................................................................................................ 459Comparing Transport and Tunnel Modes .................................................................. 459
IPsec Security Constructs ............................................................................................... 462Security Policies, Security Associations, and Associated Databases ............................. 462Selectors .............................................................................................................. 463Security Association Triples and Security Parameter Index (SPI) ................................... 463
IPsec Authentication Header (AH) ................................................................................... 463AH Datagram Placement and Linking .......................................................................464AH Format ............................................................................................................ 467
IPsec Encapsulating Security Payload (ESP) ......................................................................468ESP Fields ............................................................................................................. 468ESP Operations and Field Use ................................................................................ 469ESP Format ........................................................................................................... 472
30INTERNET PROTOCOL MOBIL ITY SUPPORT (MOBILE IP) 477
Mobile IP Overview, History, and Motivation ................................................................... 478The Problem with Mobile Nodes in TCP/IP ............................................................... 478The Solution: Mobile IP .......................................................................................... 480Limitations of Mobile IP .......................................................................................... 481
Mobile IP Concepts and General Operation .................................................................... 482Mobile IP Device Roles ...........................................................................................483Mobile IP Functions ................................................................................................ 484
Mobile IP Addressing: Home and Care-Of Addresses ....................................................... 485Foreign Agent Care-Of Address .............................................................................. 486
Mobile IP Agent Discovery ............................................................................................488Agent Discovery Process ........................................................................................ 488Agent Advertisement and Agent Solicitation Messages ............................................... 488
Mobile IP Home Agent Registration and Registration Messages .......................................... 493Mobile Node Registration Events ............................................................................. 493Registration Request and Registration Reply Messages ............................................... 493Registration Process ............................................................................................... 494Registration Request Message Format ......................................................................495Registration Reply Message Format ......................................................................... 497
Mobile IP Data Encapsulation and Tunneling ................................................................... 497Mobile IP Conventional Tunneling ........................................................................... 498Mobile IP Reverse Tunneling ................................................................................... 500
Mobile IP and TCP/IP Address Resolution Protocol (ARP) Operation ................................... 500Mobile IP Efficiency Issues .............................................................................................502Mobile IP Security Considerations ..................................................................................505
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PART II -6IP SUPPORT PROTOCOLS
31ICMP CONCEPTS AND GENERAL OPERATION 509
ICMP Overview, History, Versions, and Standards ...........................................................510ICMP General Operation .............................................................................................. 512
The ICMP Message-Passing Service ......................................................................... 512ICMP Error-Reporting Limited to the Datagram Source ................................................513
ICMP Message Classes, Types, and Codes ..................................................................... 514ICMP Message Classes .......................................................................................... 514ICMP Message Types ............................................................................................514ICMP Message Codes ...........................................................................................515ICMP Message Class and Type Summary ................................................................. 515
ICMP Message Creation and Processing Conventions and Rules ........................................ 517Limitations on ICMP Message Responses .................................................................. 518ICMP Message Processing Conventions ................................................................... 519
ICMP Common Message Format and Data Encapsulation .................................................520ICMP Common Message Format ............................................................................. 520Original Datagram Inclusion in ICMP Error Messages ................................................521ICMP Data Encapsulation ....................................................................................... 522
ICMPv4 Source Quench Messages .................................................................................527ICMPv4 Source Quench Message Format ................................................................. 528Problems with Source Quench Messages .................................................................. 528
ICMPv4 Time Exceeded Messages .................................................................................529ICMPv4 Time Exceeded Message Format ................................................................. 530Applications of Time Exceeded Messages ................................................................ 531
ICMPv4 Redirect Messages ...........................................................................................532ICMPv4 Redirect Message Format ........................................................................... 533Redirect Message Interpretation Codes .................................................................... 534Limitations of Redirect Messages ............................................................................. 535
ICMPv4 Parameter Problem Messages ............................................................................ 535ICMPv4 Parameter Problem Message Format ............................................................536Parameter Problem Message Interpretation Codes and the Pointer Field ....................... 536
ICMPv4 Echo (Request) and Echo Reply Messages ...........................................................540ICMPv4 Echo and Echo Reply Message Format ......................................................... 540Application of Echo and Echo Reply Messages ......................................................... 541
ICMPv4 Timestamp (Request) and Timestamp Reply Messages ........................................... 541ICMPv4 Timestamp and Timestamp Reply Message Format ........................................ 542Issues Using Timestamp and Timestamp Reply Messages ............................................ 543
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ICMPv4 Router Advertisement and Router Solicitation Messages ........................................ 543The Router Discovery Process ..................................................................................544ICMPv4 Router Advertisement Message Format ......................................................... 544ICMPv4 Router Solicitation Message Format ............................................................. 546Addressing and Use of Router Advertisement and Router Solicitation Messages ............ 546
ICMPv4 Address Mask Request and Reply Messages ........................................................ 547ICMPv4 Address Mask Request and Address Mask Reply Message Format ................... 547Use of Address Mask Request and Address Mask Reply Messages .............................. 548
ICMPv4 Traceroute Messages ........................................................................................ 548ICMPv4 Traceroute Message Format ........................................................................ 549Use of Traceroute Messages ................................................................................... 550
ICMPv6 Packet Too Big Messages ..................................................................................554ICMPv6 Packet Too Big Message Format .................................................................. 555Applications of Packet Too Big Messages ................................................................. 555
ICMPv6 Time Exceeded Messages .................................................................................556ICMPv6 Time Exceeded Message Format ................................................................. 557Applications of Time Exceeded Messages ................................................................ 558
ICMPv6 Parameter Problem Messages ............................................................................ 558ICMPv6 Parameter Problem Message Format ............................................................559Parameter Problem Message Interpretation Codes and the Pointer Field ....................... 559
35ICMPV6 INFORMATIONAL MESSAGE TYPES AND FORMATS 561
ICMPv6 Echo Request and Echo Reply Messages ............................................................. 562ICMPv6 Echo and Echo Reply Message Format ......................................................... 562Application of Echo and Echo Reply Messages ......................................................... 563
ICMPv6 Router Advertisement and Router Solicitation Messages ........................................ 564ICMPv6 Router Advertisement Message Format ......................................................... 564ICMPv6 Router Solicitation Message Format ............................................................. 566Addressing of Router Advertisement and Router Solicitation Messages ......................... 566
ICMPv6 Neighbor Advertisement and Neighbor Solicitation Messages ............................... 567ICMPv6 Neighbor Advertisement Message Format .................................................... 567ICMPv4 Neighbor Solicitation Message Format ........................................................ 568Addressing of Neighbor Advertisement and Neighbor Solicitation Messages ............... 570
ICMPv6 Redirect Messages ...........................................................................................570ICMPv6 Redirect Message Format ........................................................................... 570Application of Redirect Messages ............................................................................ 571
ICMPv6 Informational Message Options ......................................................................... 574Source Link-Layer Address Option Format ................................................................. 575Target Link-Layer Address Option Format .................................................................. 576Prefix Information Option Format ............................................................................. 576
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Redirected Header Option Format ........................................................................... 578MTU Option Format ............................................................................................... 579
36IPV6 NEIGHBOR DISCOVERY (ND) PROTOCOL 581
IPv6 ND Overview .......................................................................................................582Formalizing Local Network Functions: The Neighbor Concept .....................................583Neighbor Discovery Standards ............................................................................... 583
IPv6 ND General Operational Overview ......................................................................... 584Host-Router Discovery Functions .............................................................................. 585Host-Host Communication Functions ......................................................................... 585Redirect Function ................................................................................................... 585Relationships Between Functions .............................................................................. 586ICMPv6 Messages Used by ND .............................................................................. 586
Host-Router Discovery Functions Performed by Routers ................................................588Host-Router Discovery Functions Performed by Hosts .................................................. 589
IPv6 ND Host-Host Communication Functions ................................................................... 589Next-Hop Determination ......................................................................................... 590Address Resolution ................................................................................................ 590Updating Neighbors Using Neighbor Advertisement Messages ................................... 591Neighbor Unreachability Detection and the Neighbor Cache .....................................591Duplicate Address Detection ................................................................................... 592
IPv6 ND Redirect Function .............................................................................................592
PART II -7TCP/IP ROUTING PROTOCOLS (GATEWAY PROTOCOLS)
Static and Dynamic Routing Protocols ............................................................................. 601
38ROUTING INFORMATION PROTOCOL (RIP, RIP-2, AND RIPNG) 603
RIP Overview ............................................................................................................... 604RIP Standardization ............................................................................................... 604RIP Operational Overview, Advantages, and Limitations ............................................ 605Development of RIP Version 2 (RIP-2) and RIPng for IPv6 ............................................. 606
RIP Route Determination Algorithm and Metric ................................................................. 606RIP Routing Information and Route Distance Metric .................................................... 606RIP Route Determination Algorithm ........................................................................... 607
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RIP Route Determination and Information Propagation ................................................607Default Routes .......................................................................................................610
RIP General Operation, Messaging, and Timers ............................................................... 610RIP Messages and Basic Message Types .................................................................. 610RIP Update Messaging and the 30-Second Timer ...................................................... 611Preventing Stale Information: The Timeout Timer ........................................................ 611Removing Stale Information: The Garbage-Collection Timer ........................................ 612Triggered Updates ................................................................................................. 612
RIP Problems and Some Resolutions ................................................................................ 612Issues with RIP’s Algorithm ...................................................................................... 613Issues with RIP’s Metric ...........................................................................................616RIP Special Features for Resolving RIP Algorithm Problems .......................................... 617
RIP Version-Specific Message Formats and Features .......................................................... 620RIP Version 1 (RIP-1) Message Format and Features ................................................... 620RIP Version 2 (RIP-2) Message Format and Features ................................................... 623RIPng (RIPv6) Message Format and Features ............................................................. 626
39OPEN SHORTEST PATH FIRST (OSPF) 631
OSPF Overview ........................................................................................................... 632Development and Standardization of OSPF .............................................................. 632Overview of OSPF Operation .................................................................................633OSPF Features and Drawbacks ............................................................................... 633
OSPF Basic Topology and the Link-State Database ...........................................................634OSPF Basic Topology ............................................................................................634LSDB Information Storage and Propagation .............................................................. 635
OSPF Hierarchical Topology .......................................................................................... 636OSPF Areas .......................................................................................................... 636Router Roles in OSPF Hierarchical Topology ............................................................. 637
OSPF Route Determination Using SPF Trees ..................................................................... 639The SPF Tree ......................................................................................................... 639OSPF Route Determination ...................................................................................... 640
OSPF Message Formats ................................................................................................ 645OSPF Common Header Format ............................................................................... 645OSPF Hello Message Format ..................................................................................647OSPF Database Description Message Format ............................................................647OSPF Link State Request Message Format ................................................................. 649OSPF Link State Update Message Format ................................................................. 649OSPF Link State Acknowledgment Message Format ................................................... 650OSPF Link State Advertisements and the LSA Header Format ....................................... 650
40BORDER GATEWAY PROTOCOL (BGP/BGP-4) 653
BGP Overview ............................................................................................................. 654BGP Versions and Defining Standards ..................................................................... 655Overview of BGP Functions and Features ................................................................. 656
BGP Route Determination and the BGP Decision Process ................................................... 666BGP Decision Process Phases ..................................................................................666Criteria for Assigning Preferences to Routes .............................................................. 666Limitations on BGP’s Ability to Select Efficient Routes .................................................. 667Originating New Routes and Withdrawing Unreachable Routes ................................. 668
BGP General Operation and Messaging ......................................................................... 668Speaker Designation and Connection Establishment .................................................. 668Route Information Exchange ................................................................................... 669Connectivity Maintenance ...................................................................................... 669Error Reporting ..................................................................................................... 669
BGP Detailed Messaging, Operation, and Message Formats ............................................. 670BGP Message Generation and Transport .................................................................. 670BGP General Message Format ................................................................................ 670BGP Connection Establishment: Open Messages ....................................................... 672BGP Route Information Exchange: Update Messages ................................................674BGP Connectivity Maintenance: Keepalive Messages ............................................... 677BGP Error Reporting: Notification Messages ............................................................. 680
Two Protocols for TCP/IP Transport Layer Requirements ..................................................... 698Applications of TCP and UDP ........................................................................................ 699
Summary Comparison of UDP and TCP ........................................................................... 700
43TCP AND UDP ADDRESSING: PORTS AND SOCKETS 703
TCP/IP Processes, Multiplexing, and Client/Server Application Roles ................................. 704Multiplexing and Demultiplexing ............................................................................. 704TCP/IP Client Processes and Server Processes ...........................................................705
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Multiplexing and Demultiplexing Using Ports ............................................................. 707Source Port and Destination Port Numbers ................................................................ 707Summary of Port Use for Datagram Transmission and Reception .................................. 709
TCP/IP Application Assignments and Server Port Number Ranges ......................................709Reserved Port Numbers .......................................................................................... 710TCP/UDP Port Number Ranges ............................................................................... 710
TCP/IP Client (Ephemeral) Ports and Client/Server Application Port Use ............................. 711Ephemeral Port Number Assignment ........................................................................ 712Ephemeral Port Number Ranges .............................................................................. 713Port Number Use During a Client/Server Exchange ................................................... 713
TCP/IP Sockets and Socket Pairs: Process and Connection Identification ............................. 714Common TCP/IP Applications and Well-Known and Registered Port Numbers ..................... 715
44TCP/IP USER DATAGRAM PROTOCOL (UDP) 719
UDP Overview, History, and Standards ........................................................................... 720UDP Operation ............................................................................................................ 721
What UDP Does .................................................................................................... 721What UDP Does Not Do ........................................................................................ 721
UDP Message Format ................................................................................................... 722UDP Common Applications and Server Port Assignments .................................................. 724
Why Some TCP/IP Applications Use UDP ................................................................. 725Common UDP Applications and Server Port Use ........................................................ 726Applications That Use Both UDP and TCP ................................................................. 727
45TCP OVERVIEW, FUNCTIONS, AND CHARACTERISTICS 729
TCP Overview, History, and Standards ........................................................................... 730TCP History .......................................................................................................... 730Overview of TCP Operation ................................................................................... 731TCP Standards ......................................................................................................731
TCP Functions .............................................................................................................. 732Functions That TCP Performs ................................................................................... 733Functions That TCP Doesn’t Perform ......................................................................... 733
46TRANSMISSION CONTROL PROTOCOL (TCP)FUNDAMENTALS AND GENERAL OPERATION 737
TCP Data Handling and Processing ................................................................................ 738Increasing the Flexibility of Application Data Handling:
TCP’s Stream Orientation ................................................................................ 738TCP Data Packaging: Segments .............................................................................. 738TCP Data Identification: Sequence Numbers ............................................................. 739The Need for Application Data Delimiting ................................................................ 741
TCP Sliding Window Acknowledgment System ................................................................ 741The Problem with Unreliable Protocols: Lack of Feedback ........................................... 742Providing Basic Reliability Using Positive Acknowledgment with
Retransmission (PAR) ....................................................................................... 742Improving PAR ......................................................................................................744
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TCP’s Stream-Oriented Sliding Window Acknowledgment System ............................... 744More Information on TCP Sliding Windows .............................................................. 750
TCP Ports, Connections, and Connection Identification ...................................................... 751TCP Common Applications and Server Port Assignments ................................................... 752
47TCP BASIC OPERATION: CONNECTION ESTABLISHMENT,MANAGEMENT, AND TERMINATION 755
TCP Operational Overview and the TCP Finite State Machine (FSM) ................................... 756Basic FSM Concepts .............................................................................................. 756The Simplified TCP FSM ......................................................................................... 757
TCP Connection Preparation .......................................................................................... 760Storing Connection Data: The Transmission Control Block (TCB) .................................. 761Active and Passive OPENs ..................................................................................... 761Preparation for Connection ..................................................................................... 762
TCP Connection Establishment Process: The Three-Way Handshake .................................... 762Connection Establishment Functions ......................................................................... 762Control Messages Used for Connection Establishment: SYN and ACK ......................... 763Normal Connection Establishment: The Three-Way Handshake ................................... 763Simultaneous Open Connection Establishment .......................................................... 765
TCP Connection Establishment Sequence Number Synchronizationand Parameter Exchange ................................................................................ 767
Initial Sequence Number Selection .......................................................................... 767TCP Sequence Number Synchronization .................................................................. 768TCP Parameter Exchange ....................................................................................... 769
TCP Connection Management and Problem Handling ....................................................... 770The TCP Reset Function .......................................................................................... 770Handling Reset Segments ....................................................................................... 771Idle Connection Management and Keepalive Messages ............................................. 771
TCP Connection Termination .......................................................................................... 772Requirements and Issues In Connection Termination ................................................... 772Normal Connection Termination .............................................................................. 773The TIME-WAIT State .............................................................................................775Simultaneous Connection Termination ......................................................................776
48TCP MESSAGE FORMATTING AND DATA TRANSFER 779
TCP Message (Segment) Format ..................................................................................... 780TCP Checksum Calculation and the TCP Pseudo Header ................................................... 784
Detecting Transmission Errors Using Checksums ........................................................ 784Increasing the Scope of Detected Errors: The TCP Pseudo Header ............................... 784Advantages of the Pseudo Header Method ............................................................... 786
TCP Maximum Segment Size (MSS) ................................................................................ 787MSS Selection .......................................................................................................788TCP Default MSS ................................................................................................... 788Nondefault MSS Value Specification .......................................................................789
TCP Sliding Window Data Transfer and Acknowledgment Mechanics ................................ 790Sliding Window Transmit and Receive Categories ..................................................... 790Send (SND) and Receive (RCV) Pointers ................................................................... 791TCP Segment Fields Used to Exchange Pointer Information ......................................... 793An Example of TCP Sliding Window Mechanics ....................................................... 794Real-World Complications of the Sliding Window Mechanism .................................... 797
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TCP Immediate Data Transfer: Push Function .................................................................... 799TCP Priority Data Transfer: Urgent Function ..................................................................... 800
49TCP RELIABILITY AND FLOW-CONTROL FEATURES 803
TCP Segment Retransmission Timers and the Retransmission Queue .................................... 804Managing Retransmissions Using the Retransmission Queue ....................................... 804Recognizing When a Segment Is Fully Acknowledged ............................................... 805
TCP Adaptive Retransmission and Retransmission Timer Calculations .................................. 813Adaptive Retransmission Based on RTT Calculations .................................................. 813Acknowledgment Ambiguity ................................................................................... 814Refinements to RTT Calculation and Karn’s Algorithm .................................................814
TCP Window Size Adjustment and Flow Control .............................................................. 815Reducing Send Window Size to Reduce the Rate Data Is Sent .................................... 816Reducing Send Window Size to Stop the Sending of New Data ................................. 818Closing the Send Window ...................................................................................... 818
TCP Window-Management Issues ................................................................................... 819Problems Associated with Shrinking the TCP Window ................................................819Reducing Buffer Size Without Shrinking the Window .................................................820Handling a Closed Window and Sending Probe Segments ........................................ 821
PART II I -1NAME SYSTEMS AND TCP/IP NAME REGISTRATION AND NAME RES OLUTION
50NAME SYSTEM ISSUES, CONCEPTS, AND TECHNIQUES 835
Name System Overview ................................................................................................ 836Symbolic Names for Addressing ............................................................................. 836A Paradox: Name Systems Are Both Essential and Unnecessary .................................. 836Basic Name System Functions: Name Space, Name Registration, and Name Resolution 839
Name Spaces and Name Architectures ........................................................................... 841Name Space Functions .......................................................................................... 841Flat Name Architecture (Flat Name Space) ............................................................... 842Hierarchical Name Architecture .............................................................................. 842Comparing Name Architectures .............................................................................. 843
Name Registration Methods, Administration, and Authorities ............................................. 844Name Registration Functions ................................................................................... 844Hierarchical Name Registration .............................................................................. 845
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Name Registration Methods .................................................................................... 845Name Resolution Techniques and Elements ......................................................................846
Name Resolution Methods ...................................................................................... 847Client/Server Resolution Functional Elements ............................................................848
Efficiency, Reliability, and Other Name Resolution Considerations .....................................848Efficiency Considerations ....................................................................................... 849Reliability Considerations ....................................................................................... 849Other Considerations .............................................................................................850
51TCP/IP NAME SYSTEMS OVERVIEW ANDTHE HOST TABLE NAME SYSTEM 851
A Brief History of TCP/IP Host Names and Name Systems ................................................852Developing the First Name System: ARPAnet Host Name Lists .....................................852Storing Host Names in a Host Table File .................................................................. 852Outgrowing the Host Table Name System and Moving to DNS ................................... 853
The TCP/IP Host Table Name System .............................................................................. 853Host Table Name Resolution ................................................................................... 854Host Table Name Registration .................................................................................854Weaknesses of the Host Table Name System ............................................................855Use of the Host Table Name System in Modern Networking ....................................... 856
52DOMAIN NAME SYSTEM (DNS) OVERVIEW, FUNCTIONS,AND CHARACTERISTICS 857
DNS Overview, History, and Standards .......................................................................... 858Early DNS Development and the Move to Hierarchical Domains ................................. 858Standardization of DNS and Initial Defining Standards .............................................. 859DNS Evolution and Important Additional Standards ................................................... 860DNS Adaptation for Internet Protocol Version 6 ......................................................... 860
DNS Design Goals, Objectives, and Assumptions ............................................................861DNS Design Goals and Objectives .......................................................................... 861DNS Design Assumptions ....................................................................................... 862
DNS Components and General Functions ........................................................................ 863DNS Name Space ................................................................................................ 863Name Registration (Including Administration and Authorities) .....................................864Name Resolution ................................................................................................... 864
53DNS NAME SPACE, ARCHITECTURE, AND TERMINOLOGY 867
DNS Domains and the DNS Hierarchical Name Architecture ............................................. 868The Essential Concept in the DNS Name Space: Domains .......................................... 868The DNS Hierarchical Tree Structure of Names ......................................................... 868
DNS Structural Elements and Terminology .......................................................................870DNS Tree-Related Terminology ................................................................................ 870DNS Domain-Related Terminology ........................................................................... 870DNS Family-Related Terminology ............................................................................. 871
DNS Labels, Names, and Syntax Rules ........................................................................... 873DNS Labels and Label Syntax Rules ......................................................................... 873Domain Name Construction .................................................................................... 874
Absolute (Fully Qualified) and Relative (Partially Qualified) Domain Name Specifications .....875
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54DNS NAME REGISTRATION, PUBLIC ADMINISTRATION,ZONES, AND AUTHORITIES 877
DNS Hierarchical Authority Structure and the Distributed Name Database ..........................878The DNS Root Domain Central Authority .................................................................. 878TLD Authorities ......................................................................................................879Lower-Level Authority Delegation ............................................................................. 879Authority Hierarchy’s Relationship to the Name Hierarchy ......................................... 879The DNS Distributed Name Database ......................................................................880
DNS Organizational (Generic) TLDs and Authorities ......................................................... 880Original Generic TLDs ...........................................................................................881New Generic TLDs ................................................................................................ 881
DNS Geopolitical (Country Code) TLDs and Authorities ..................................................... 884Country Code Designations .................................................................................... 884Country Code TLD Authorities .................................................................................885Leasing/Sale of Country Code Domains ................................................................... 885Drawbacks of the Geopolitical TLDs ......................................................................... 886
Public Registration for Second-Level and Lower Domains ................................................... 886Registration Authority .............................................................................................887Registration Coordination ....................................................................................... 888
DNS Public Registration Disputes and Dispute Resolution ................................................... 888Public Registration Disputes .................................................................................... 888Methods of Registration Dispute Resolution ............................................................... 890The Uniform Domain Name Dispute Resolution Policy ................................................890
DNS Name Space Administrative Hierarchy Partitioning: DNS Zones of Authority ............... 891Methods of Dividing a Name Space into Zones of Authority ....................................... 892The Impact of Zones on Name Resolution: Authoritative Servers .................................. 892
DNS Private Name Registration ..................................................................................... 894Using Publicly Accessible Private Names ................................................................. 894Using Private Names for Internal Use .......................................................................895Using Private Names on Networks Not Connected to the Internet ................................ 895
55DNS NAME SERVER CONCEPTS AND OPERATION 897
DNS General Operation ............................................................................................... 898DNS Name Server Architecture and the Distributed Name Database ...........................898DNS Server Support Functions ................................................................................ 899The Logical Nature of the DNS Name Server Hierarchy ............................................. 900
DNS Name Server Data Storage .................................................................................... 900Binary and Text Representations of Resource Records (RRs) ......................................... 900Use of RRs and Master Files .................................................................................... 901Common RR Types ................................................................................................. 902RR Classes ............................................................................................................ 903
DNS Name Server Types and Roles ............................................................................... 903Master (Primary)/Slave (Secondary) Servers ............................................................. 903Name Server Roles ................................................................................................ 905Caching-Only Name Servers ..................................................................................905
DNS Zone Management, Contacts, and Zone Transfers .................................................... 905Domain Contacts ................................................................................................... 906
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Zone Transfers ......................................................................................................906DNS Root Name Servers ............................................................................................... 909
Root Name Server Redundancy ............................................................................... 909Current Root Name Servers .................................................................................... 910
DNS Name Server Caching .......................................................................................... 911Name Server Caching ...........................................................................................912Caching Data Persistence and the Time to Live Interval ............................................... 912Negative Caching ................................................................................................. 914
DNS Name Server Load Balancing ................................................................................ 914Using Multiple Address Records to Spread Out Requests to a Domain ..........................914Using Multiple DNS Servers to Spread Out DNS Requests .......................................... 915
DNS Name Server Enhancements ..................................................................................915Automating Zone Transfers: DNS Notify ................................................................... 916Improving Zone Transfer Efficiency: Incremental Transfers ........................................... 917Dealing with Dynamic IP Addresses: DNS Update/Dynamic DNS ............................... 917
56DNS RESOLUTION CONCEPTS AND RESOLVER OPERATIONS 919
DNS Resolver Functions and General Operation .............................................................. 920Name Resolution Services ...................................................................................... 920Functions Performed by Name Resolvers .................................................................. 920
DNS Name Resolution Techniques: Iterative and Recursive Resolution ................................. 922Iterative Resolution ................................................................................................. 923Recursive Resolution ............................................................................................... 924Contrasting Iterative and Recursive Resolution ...........................................................924
DNS Name Resolution Efficiency Improvements: Caching and Local Resolution .................... 925The Motivation for Caching: Locality of Reference ..................................................... 926Name Resolver Caching ........................................................................................ 926Local Resolution .................................................................................................... 927
DNS Name Resolution Process ....................................................................................... 928A Simple Example of DNS Name Resolution ............................................................928Changes to Resolution to Handle Aliases (CNAME Records) ....................................... 930
DNS Reverse Name Resolution Using the IN-ADDR.ARPA Domain ......................................931The Original Method: Inverse Querying ................................................................... 931The IN-ADDR.ARPA Name Structure for Reverse Resolution ......................................... 932RR Setup for Reverse Resolution ............................................................................... 932
DNS Electronic Mail Support and Mail Exchange (MX) ResourceRecords ............................934Special Requirements for Email Name Resolution ...................................................... 935The Mail Exchange (MX) Record and Its Use ............................................................. 935
57DNS MESSAGING AND MESSAGE, RESOURCE RECORD,AND MASTER FILE FORMATS 937
DNS Message Generation and Transport ........................................................................ 938DNS Client/Server Messaging Overview ................................................................. 938DNS Message Transport Using UDP and TCP ...........................................................939DNS Message Processing and General Message Format ........................................... 940
DNS Message Header Format ....................................................................................... 942DNS Question Section Format ....................................................................................... 945DNS Message Resource Record Field Formats ................................................................. 945
DNS Common RR Format ....................................................................................... 946RData Field Formats for Common RRs ......................................................................946
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DNS Name Notation and Message Compression ............................................................950Standard DNS Name Notation ............................................................................... 950DNS Electronic Mail Address Notation .................................................................... 951DNS Message Compression ................................................................................... 951
DNS Master File Format ................................................................................................ 953DNS Common Master File Record Format ................................................................ 954Use and Interpretation of Partially Qualified Domain Names (PQDNs) ......................... 954Master File Directives .............................................................................................955Syntax Rules for Master Files ................................................................................... 955Specific RR Syntax and Examples ............................................................................ 956Sample Master File ................................................................................................ 958
DNS Changes to Support IPv6 ....................................................................................... 958IPv6 DNS Extensions .............................................................................................. 959Proposed Changes to the IPv6 DNS Extensions ......................................................... 959
PART II I -2NETWORK FILE AND RESOURCE SHARING PROTOCOLS AND THE TCP/IP NETWORK FILE SYSTEM (NFS)
58NETWORK FILE AND RESOURCE SHARING ANDTHE TCP/IP NETWORK FILE SYSTEM (NFS) 963
File and Resource Sharing Concepts and Components ...................................................... 964The Power of File and Resource Sharing Protocols ..................................................... 964Components of a File and Resource Sharing Protocol .................................................964
NFS Design Goals, Versions, and Standards ................................................................... 965NFS Design Goals ................................................................................................. 965NFS Versions and Standards ..................................................................................966
NFS Architecture and Components .................................................................................967NFS Main Components .......................................................................................... 967Other Important NFS Functions ............................................................................... 968
NFS Data Definition with the External Data Representation (XDR) Standard ......................... 969A Method of Universal Data Exchange: XDR ............................................................. 969XDR Data Types .................................................................................................... 970
NFS Client/Server Operation Using Remote Procedure Calls (RPCs) ................................... 971RPC Operation and Transport Protocol Usage ...........................................................972Client and Server Responsibilities in NFS ................................................................. 973Client and Server Caching ..................................................................................... 973
NFS Server Procedures and Operations .......................................................................... 974NFS Version 2 and Version 3 Server Procedures ....................................................... 974NFS Version 4 Server Procedures and Operations ..................................................... 976
NFS File System Model and the Mount Protocol ............................................................... 978The NFS File System Model .................................................................................... 978The Mount Protocol ................................................................................................ 978
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PART II I -3HOST CONFIGURATION AND TCP/IP HOST CONFIGURATION PROTO COLS
59HOST CONFIGURATION CONCEPTS, ISSUES, AND MOTIVATION 983
The Purpose of Host Configuration .................................................................................983The Problems with Manual Host Configuration ................................................................. 984Automating the Process: Host Configuration Protocols ....................................................... 985The Role of Host Configuration Protocols in TCP/IP ...........................................................985
60TCP/IP BOOTSTRAP PROTOCOL (BOOTP) 987
BOOTP Overview, History, and Standards ......................................................................988BOOTP: Correcting the Weaknesses of RARP ...........................................................988Vendor-Specific Parameters .................................................................................... 989Changes to BOOTP and the Development of DHCP ................................................... 990
BOOTP Client/Server Messaging and Addressing ............................................................990BOOTP Messaging and Transport ........................................................................... 991BOOTP Use of Broadcasts and Ports ........................................................................ 991Retransmission of Lost Messages ............................................................................. 992
BOOTP Detailed Operation ...........................................................................................993BOOTP Bootstrapping Procedure ............................................................................. 993Interpretation of the Client IP Address (CIAddr) Field .................................................. 994
BOOTP Message Format ............................................................................................... 995BOOTP Vendor-Specific Area and Vendor Information Extensions ......................................998
BOOTP Vendor Information Extensions ..................................................................... 999BOOTP Vendor Information Fields ......................................................................... 1000
BOOTP Relay Agents (Forwarding Agents) ....................................................................1001The Function of BOOTP Relay Agents .....................................................................1002Normal BOOTP Operation Using a Relay Agent ..................................................... 1002Relaying BOOTP Requests Using Broadcasts ........................................................... 1003
61DHCP OVERVIEW AND ADDRESS ALLOCATIONCONCEPTS 1007
DHCP Overview, History, and Standards ...................................................................... 1008DHCP: Building on BOOTP’s Strengths ................................................................... 1009Overview of DHCP Features ................................................................................. 1009
DHCP Lease Life Cycle and Lease Timers ....................................................................... 1015DHCP Lease Life Cycle Phases .............................................................................. 1016Renewal and Rebinding Timers ............................................................................. 1016
DHCP Lease Address Pools, Ranges, and Address Management ...................................... 1018
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Address Pool Size Selection .................................................................................. 1018Lease Address Ranges (Scopes) ............................................................................ 1019Other Issues with Address Management ................................................................. 1020
62DHCP CONFIGURATION AND OPERATION 1023
DHCP Overview of Client and Server Responsibilities ..................................................... 1024DHCP Server Responsibilities ................................................................................1024DHCP Client Responsibilities ................................................................................. 1025DHCP Client/Server Roles .................................................................................... 1025DHCP Relay Agents ............................................................................................. 1026
DHCP Configuration Parameters, Storage, and Communication ....................................... 1026Configuration Parameter Management ................................................................... 1026Parameter Storage ............................................................................................... 1027Configuration Parameter Communication ............................................................... 1027
DHCP General Operation and the Client Finite State Machine ......................................... 1027DHCP Lease Allocation, Reallocation, and Renewal ........................................................ 1031
Initial Lease Allocation Process .............................................................................. 1031DHCP Lease Reallocation Process .......................................................................... 1036DHCP Lease Renewal and Rebinding Processes ....................................................... 1038DHCP Early Lease Termination (Release) Process ..................................................... 1041
DHCP Parameter Configuration Process for Clients with Non-DHCP Addresses ................... 1043
63DHCP MESSAGING, MESSAGE TYPES, AND FORMATS 1045
DHCP Message Generation, Addressing, Transport, and Retransmission ........................... 1046Message Generation and General Formatting ........................................................ 1046Message Transport .............................................................................................. 1046Retransmission of Lost Messages ........................................................................... 1047
DHCP Message Format ............................................................................................... 1048DHCP Options ........................................................................................................... 1051
Options and Option Format .................................................................................. 1052Option Categories ............................................................................................... 1053Option Overloading ............................................................................................ 1054
Summary of DHCP Options/BOOTP Vendor Information Fields ........................................ 1055RFC 1497 Vendor Extensions ...............................................................................1055IP Layer Parameters Per Host ................................................................................. 1057IP Layer Parameters Per Interface ........................................................................... 1057Link Layer Parameters Per Interface ........................................................................ 1058TCP Parameters ................................................................................................... 1058Application and Service Parameters ...................................................................... 1058DHCP Extensions ................................................................................................. 1060
64DHCP CLIENT/SERVER IMPLEMENTATION, FEATURES,AND IPV6 SUPPORT 1063
DHCP Server and Client Implementation and Management Issues ....................................1064DHCP Server Implementations ...............................................................................1064DHCP Client Implementations ................................................................................1066
DHCP Message Relaying and BOOTP Relay Agents ....................................................... 1066Use of BOOTP Relay Agents for DHCP ................................................................... 1067
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DHCP Relaying Process ........................................................................................ 1067DHCP Autoconfiguration/Automatic Private IP Addressing (APIPA) ...................................1068
DHCP Server Conflict Detection .................................................................................... 1071DHCP and BOOTP Interoperability ...............................................................................1072
BOOTP Clients Connecting to a DHCP Server .........................................................1073DHCP Clients Connecting to a BOOTP Server .........................................................1073
DHCP for IP Version 6 (DHCPv6) .................................................................................. 1075Two Methods for Autoconfiguration in IPv6 ............................................................. 1075DHCPv6 Operation Overview ...............................................................................1075DHCPv6 Message Exchanges ...............................................................................1076
PART II I -4TCP/IP NETWORK MANAGEMENT FRAMEWORK AND PROTOCOLS
65TCP/IP INTERNET STANDARD MANAGEMENTFRAMEWORK OVERVIEW 1079
Overview and History of the TCP/IP Internet Standard Management Frameworkand Simple Network Management Protocol (SNMP) ......................................... 1080
Early Development of SNMP ................................................................................. 1080The Two Meanings of SNMP ................................................................................1081Design Goals of SNMP ........................................................................................ 1081Further Development of SNMP and the Problem of SNMP Variations .........................1082
TCP/IP SNMP Operational Model, Components, and Terminology .................................. 1082SNMP Device Types ............................................................................................ 1082SNMP Entities .....................................................................................................1083SNMP Operational Model Summary .....................................................................1083
TCP/IP Internet Standard Management Framework Architecture and Protocol Components .. 1085SNMP Framework Components ............................................................................. 1085SNMP Framework Architecture ............................................................................. 1086
TCP/IP Internet Standard Management Framework and SNMP Versions(SNMPv1, SNMPv2 Variants, and SNMPv3) ................................................... 1087
TCP/IP MIB Objects, Object Characteristics, and Object Types ....................................... 1099
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MIB Object Characteristics ................................................................................... 1099SMI Data Types ................................................................................................... 1101
TCP/IP MIB Object Descriptors and Identifiers and the Object Name Hierarchy ................. 1102Object Descriptors ............................................................................................... 1103Object Identifiers ................................................................................................. 1103Structure of the MIB Object Name Hierarchy ..........................................................1104Recursive Definition of MIB Object Identifiers ..........................................................1106
TCP/IP MIB Modules and Object Groups ...................................................................... 1106The Organization of MIB Objects into Object Groups ..............................................1106MIB Modules ...................................................................................................... 1108MIB Module Format ............................................................................................. 1109
67TCP/IP SIMPLE NETWORK MANAGEMENT PROTOCOL(SNMP) CONCEPTS AND OPERATION 1111
SNMP Protocol Overview ............................................................................................ 1112Early Development of SNMPv1 ............................................................................. 1112SNMPv2 and the Division of SNMP into Protocol Operations and Transport Mappings 1113SNMP Communication Methods ............................................................................ 1114
SNMP Protocol Operations ..........................................................................................1114SNMP PDU Classes ............................................................................................. 1115Basic Request/Response Information Poll Using GetRequest
and (Get)Response Messages ........................................................................ 1116Table Traversal Using GetNextRequest and GetBulkRequest Messages ....................... 1117Object Modification Using SetRequest Messages ..................................................... 1119Information Notification Using Trap and InformRequest Messages ............................. 1121
SNMP Protocol Security Issues and Methods .................................................................. 1122Problems with SNMPv1 Security ............................................................................ 1123SNMPv2/v3 Security Methods .............................................................................. 1123
68SNMP PROTOCOL MESSAGING AND MESSAGE FORMATS 1125
SNMP Protocol Message Generation ............................................................................ 1126SNMP Transport Mappings .........................................................................................1126
SNMP General Message Format .................................................................................. 1128The Difference Between SNMP Messages and PDUs ................................................ 1129General PDU Format ............................................................................................ 1129
SNMP Version 1 (SNMPv1) Message Format ................................................................ 1131SNMPv1 General Message Format ....................................................................... 1131SNMPv1 PDU Formats .........................................................................................1132
SNMP Version 2 (SNMPv2) Message Formats ............................................................... 1134SNMP Version 2 (SNMPv2p) Message Format ........................................................ 1135Community-Based SNMP Version 2 (SNMPv2c) Message Format .............................. 1136User-Based SNMP Version 2 (SNMPv2u) Message Format ....................................... 1136SNMPv2 PDU Formats .........................................................................................1138
SNMP Version 3 (SNMPv3) Message Format ................................................................ 1141
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69TCP/IP REMOTE NETWORK MONITORING (RMON) 1145
RMON Standards ...................................................................................................... 1146RMON MIB Hierarchy and Object Groups ....................................................................1146RMON Alarms, Events, and Statistics ............................................................................ 1148
PART II I -5TCP/IP APPLICATION LAYER ADDRESSING AND APPLICATION CATE GORIES
URI Overview and Standards ....................................................................................... 1152URI Categories: URLs and URNs ............................................................................ 1153URI Standards .....................................................................................................1154
URL General Syntax ....................................................................................................1154Common Internet Scheme Syntax .......................................................................... 1155Omission of URL Syntax Elements .......................................................................... 1156URL Fragments ....................................................................................................1157Unsafe Characters and Special Encodings .............................................................. 1157
URL Relative Syntax and Base URLs .............................................................................. 1162Interpretation Rules for Relative URLs ...................................................................... 1163Practical Interpretation of Relative URLs .................................................................. 1164
URL Length and Complexity Issues ................................................................................1166URL Wrapping and Delimiting .............................................................................. 1167Explicit URL Delimiting and Redirectors ................................................................... 1168URL Abbreviation ................................................................................................ 1168
URL Obscuration, Obfuscation, and General Trickery ..................................................... 1168URNs ........................................................................................................................ 1171
The Problem With URLs ........................................................................................ 1171Overview of URNs .............................................................................................. 1172URN Namespaces and Syntax .............................................................................. 1172URN Resolution and Implementation Difficulties ....................................................... 1173
71FILE AND MESSAGE TRANSFER OVERVIEW ANDAPPLICATION CATEGORIES 1175
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General File Transfer Applications ......................................................................... 1176Message Transfer Applications ............................................................................. 1176The Merging of File and Message Transfer Methods ................................................ 1177
PART II I -6TCP/IP GENERAL FILE TRANSFER PROTOCOLS
72FILE TRANSFER PROTOCOL (FTP) 1181
FTP Overview, History, and Standards .......................................................................... 1182FTP Development and Standardization ................................................................... 1182Overview of FTP Operation .................................................................................. 1183
FTP Operational Model, Protocol Components, and Key Terminology ............................... 1184The Server-FTP Process and User-FTP Process ........................................................... 1184FTP Control Connection and Data Connection .........................................................1184FTP Process Components and Terminology ............................................................. 1185Server-FTP Process Components ............................................................................. 1185User-FTP Process Components ...............................................................................1186Third-Party File Transfer (Proxy FTP) ........................................................................ 1186
FTP Control Connection Establishment, User Authentication, and Anonymous FTP Access ....1187FTP Login Sequence and Authentication ................................................................. 1187FTP Security Extensions ........................................................................................ 1188Anonymous FTP ................................................................................................... 1189
FTP Data Connection Management ...............................................................................1189Normal (Active) Data Connections ......................................................................... 1190Passive Data Connections ..................................................................................... 1190Efficiency and Security Issues Related to the Connection Methods .............................. 1191
FTP General Data Communication and Transmission Modes ............................................ 1193Stream Mode ...................................................................................................... 1193Block Mode ........................................................................................................ 1194Compressed Mode .............................................................................................. 1194
FTP Data Representation: Data Types, Format Control, and Data Structures ....................... 1194FTP Data Types ................................................................................................... 1195ASCII Data Type Line-Delimiting Issues ................................................................... 1196FTP Format Control .............................................................................................. 1196FTP Data Structures .............................................................................................. 1197
FTP Internal Command Groups and Protocol Commands ................................................. 1197FTP Command Groups and Commands .................................................................. 1197
FTP Replies ................................................................................................................1200Advantages of Using Both Text and Numeric Replies ...............................................1200Reply Code Structure and Digit Interpretation ..........................................................1201FTP Multiple-Line Text Replies ................................................................................1204
FTP User Interface and User Commands ........................................................................ 1205Command-Line and Graphical FTP Interfaces ..........................................................1205Typical FTP User Commands ................................................................................. 1206
TFTP Overview, History, and Standards ........................................................................ 1212Why TFTP Was Needed ...................................................................................... 1212Comparing FTP and TFTP ..................................................................................... 1213
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Overview of TFTP Operation ................................................................................. 1213TFTP General Operation, Connection Establishment, and Client/Server Communication ..... 1214
Connection Establishment and Identification ........................................................... 1215Lock-Step Client/Server Messaging ........................................................................ 1215Difficulties with TFTP’s Simplified Messaging Mechanism .......................................... 1216
TFTP Detailed Operation and Messaging ...................................................................... 1216Initial Message Exchange ..................................................................................... 1216Data Block Numbering .........................................................................................1217TFTP Read Process Steps ...................................................................................... 1217TFTP Write Process Steps ...................................................................................... 1218
TFTP Options and Option Negotiation .......................................................................... 1220TFTP Option Negotiation Process ........................................................................... 1220TFTP Options ...................................................................................................... 1223
PART II I -7TCP/IP ELECTRONIC MAIL SYSTEM: CONCEPTS AND PROTOCOLS
74TCP/IP ELECTRONIC MAIL SYSTEM OVERVIEW ANDCONCEPTS 1229
TCP/IP Electronic Mail System Overview and History ..................................................... 1230The Early Days of Email ....................................................................................... 1230History of TCP/IP Email ........................................................................................ 1231Overview of the TCP/IP Email System ....................................................................1231
TCP/IP Email Communication Overview ........................................................................ 1232TCP/IP Email Message Communication Model ............................................................... 1234Protocol Roles in Email Communication ......................................................................... 1236
75TCP/IP ELECTRONIC MAIL ADDRESSES AND ADDRESSING 1237
TCP/IP Email Addressing and Address Resolution ..........................................................1238Standard DNS-Based Email Addresses ................................................................... 1238Special Requirements of Email Addresses ............................................................... 1239
TCP/IP Historical and Special Email Addressing ............................................................ 1240FidoNet Addressing ............................................................................................. 1240UUCP-Style Addressing ........................................................................................ 1241Addressing for Gatewaying .................................................................................. 1241
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76TCP/IP ELECTRONIC MAIL MESSAGE FORMATS ANDMESSAGE PROCESSING: RFC 822 AND MIME 1245
TCP/IP Email RFC 822 Standard Message Format Overview .......................................... 1246Development of the RFC 822 Message Format Standard .......................................... 1247Overview of RFC 822 Messages ........................................................................... 1247General RFC 822 Message Structure .....................................................................1248
TCP/IP Email RFC 822 Standard Message Format Header Fields and Groups ................... 1249Header Field Structure .........................................................................................1249Header Field Groups ...........................................................................................1249Common Header Field Groups and Header Fields .................................................. 1250
TCP/IP Email RFC 822 Standard Message Format Processing and Interpretation ................ 1253MIME Overview ......................................................................................................... 1254
MIME Content-Type Header and Discrete Media ............................................................ 1260Content-Type Header Syntax ................................................................................. 1260Discrete Media Types and Subtypes ...................................................................... 1261
MIME Composite Media Types: Multipart and Encapsulated Message Structures ...............1265MIME Multipart Message Type .............................................................................. 1265Multipart Message Encoding ................................................................................1266MIME Encapsulated Message Type ....................................................................... 1269MIME Content-Transfer-Encoding Header and Encoding Methods .............................. 12697-Bit and 8-Bit Encoding ....................................................................................... 1270Quoted-Printable Encoding ................................................................................... 1270Base64 Encoding ................................................................................................ 1270
MIME Extension for Non-ASCII Mail Message Headers ................................................... 1273
77TCP/IP ELECTRONIC MAIL DELIVERY PROTOCOL:THE SIMPLE MAIL TRANSFER PROTOCOL (SMTP) 1275
SMTP Overview, History, and Standards ....................................................................... 1276SMTP Standards .................................................................................................. 1276SMTP Communication and Message Transport Methods ........................................... 1277Terminology: Client/Server and Sender/Receiver .................................................... 1279
SMTP Connection and Session Establishment and Termination ......................................... 1279Overview of Connection Establishment and Termination ........................................... 1280Connection Establishment and Greeting Exchange .................................................. 1280Connection Establishment Using SMTP Extensions .................................................... 1281Connection Termination ....................................................................................... 1282
SMTP Mail Transaction Process .................................................................................... 1283Overview of SMTP Mail Transaction ...................................................................... 1283SMTP Mail Transaction Details .............................................................................. 1284
SMTP Special Features, Capabilities, and Extensions ...................................................... 1286SMTP Special Features and Capabilities ................................................................. 1287SMTP Extensions ................................................................................................. 1288
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SMTP Replies and Reply Codes .................................................................................... 1293Reply Code Structure and Digit Interpretation ..........................................................1293SMTP Multiple-Line Text Replies ............................................................................. 1296Enhanced Status Code Replies .............................................................................. 1296
78TCP/IP ELECTRONIC MAIL ACCESS AND RETRIEVALPROTOCOLS AND METHODS 1297
TCP/IP Email Mailbox Access Model, Method, and Protocol Overview ............................. 1298Email Access and Retrieval Models ........................................................................ 1299
TCP/IP Post Office Protocol (POP/POP3) ....................................................................... 1300POP Overview, History, Versions, and Standards .................................................... 1300POP3 General Operation ..................................................................................... 1302POP3 Session States ............................................................................................ 1302
TCP/IP Internet Message Access Protocol (IMAP/IMAP4) ................................................ 1309IMAP Overview, History, Versions, and Standards .................................................. 1310IMAP4 General Operation ................................................................................... 1312IMAP Session States ............................................................................................ 1312IMAP Commands, Results, and Responses .............................................................. 1314IMAP4 Not Authenticated State: User Authentication Process and Commands ............. 1318IMAP4 Authenticated State: Mailbox Manipulation/Selection Process and Commands 1319IMAP4 Selected State: Message Manipulation Process and Commands ..................... 1321
TCP/IP Direct Server Email Access ................................................................................1323TCP/IP World Wide Web Email Access ....................................................................... 1325
PART II I -8TCP/IP WORLD WIDE WEB AND THE HYPERTEXT TRANSFER PROTO COL (HTTP)
79WORLD WIDE WEB AND HYPERTEXT OVERVIEW ANDCONCEPTS 1329
World Wide Web and Hypertext Overview and History ................................................. 1330History of Hypertext ............................................................................................. 1330The World Wide Web Today ...............................................................................1331
World Wide Web System Concepts and Components .................................................... 1332Major Functional Components of the Web ............................................................. 1332Web Servers and Web Browsers .......................................................................... 1333
World Wide Web Media and the Hypertext Markup Language ...................................... 1334Overview of HTML .............................................................................................. 1334HTML Elements and Tags ...................................................................................... 1335Common HTML Elements ...................................................................................... 1336Common Text Formatting Tags .............................................................................. 1338
World Wide Web Addressing: HTTP Uniform Resource Locators ...................................... 1338HTTP URL Syntax ................................................................................................. 1339Resource Paths and Directory Listings .....................................................................1340
80HTTP GENERAL OPERATION AND CONNECTIONS 1341
HTTP Versions and Standards ...................................................................................... 1342
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HTTP Operational Model and Client/Server Communication ........................................... 1345Basic HTTP Client/Server Communication ............................................................... 1345Intermediaries and the HTTP Request/Response Chain ............................................. 1346The Impact of Caching on HTTP Communication ..................................................... 1347
HTTP Transitory and Persistent Connections and Pipelining ..............................................1348Persistent Connections ..........................................................................................1349Pipelining ........................................................................................................... 1349HTTP Persistent Connection Establishment and Management ..................................... 1350
81HTTP MESSAGES, METHODS, AND STATUS CODES 1353
HTTP Generic Message Format ................................................................................... 1354HTTP Request Message Format ..................................................................................... 1355
Request Line ........................................................................................................ 1356Headers ............................................................................................................. 1358
HTTP Response Message Format .................................................................................. 1358Status Line .......................................................................................................... 1359Headers ............................................................................................................. 1360
HTTP Entities and Internet Media Types ......................................................................... 1382Media Types and Subtypes .................................................................................. 1382HTTP’s Use of Media Types .................................................................................. 1383Differences in HTTP and MIME Constructs ............................................................... 1383
HTTP Content and Transfer Encodings ........................................................................... 1384HTTP’s Two-Level Encoding Scheme ....................................................................... 1385Use of Content and Transfer Encodings .................................................................. 1385
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HTTP Data Length Issues, Chunked Transfers, and Message Trailers .................................. 1386Dynamic Data Length ...........................................................................................1387Chunked Transfers and Message Trailers ................................................................ 1387
HTTP Content Negotiation and Quality Values ............................................................... 1390Content Negotiation Techniques ............................................................................ 1390Quality Values for Preference Weights ................................................................... 1392
84HTTP FEATURES, CAPABILITIES, AND ISSUES 1393
HTTP Caching Features and Issues ................................................................................1394Benefits of HTTP Caching .................................................................................... 1394Cache Locations .................................................................................................. 1395Cache Control ....................................................................................................1396Important Caching Issues ...................................................................................... 1397
HTTP Proxy Servers and Proxying ................................................................................. 1398Benefits of Proxies ............................................................................................... 1398Comparing Proxies and Caches ............................................................................ 1399Important Proxying Issues ..................................................................................... 1399
HTTP Security and Privacy ...........................................................................................1400HTTP Authentication Methods ................................................................................1400Security and Privacy Concerns and Issues .............................................................. 1401Methods for Ensuring Privacy in HTTP ....................................................................1402
HTTP State Management Using Cookies ........................................................................ 1402Issues with Cookies .............................................................................................. 1403Managing Cookie Use .........................................................................................1404
PART II I -9OTHER FILE AND MESSAGE TRANSFER APPLICATIONS
85USENET (NETWORK NEWS) AND THE TCP/IPNETWORK NEWS TRANSFER PROTOCOL (NNTP) 1409
Usenet Overview, History, and Operation ....................................................................1410History of Usenet ................................................................................................. 1410Usenet Operation and Characteristics ....................................................................1411Usenet Transport Methods .................................................................................... 1412
Usenet Communication Model ..................................................................................... 1413Usenet’s Public Distribution Orientation .................................................................. 1414Usenet Communication Process ............................................................................. 1414Message Propagation and Server Organization ...................................................... 1416Usenet Addressing: Newsgroups ........................................................................... 1416
Usenet Message Format and Special Headers ............................................................... 1420Usenet Header Categories and Common Headers ................................................... 1420Additional Usenet Headers ................................................................................... 1422Usenet MIME Messages ....................................................................................... 1423
NNTP Overview and General Operation ...................................................................... 1423NNTP Interserver Communication Process: News Article Propagation ............................... 1425
The Usenet Server Structure .................................................................................. 1425Basic NNTP Propagation Methods ........................................................................ 1426
NNTP Client-Server Communication Process: News Posting and Access ............................ 1428News Posting, Access, and Reading ...................................................................... 1429News Access Methods .........................................................................................1430
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Other Client/Server Functions ...............................................................................1430Article Threading ................................................................................................. 1431
NNTP Commands and Command Extensions ................................................................. 1432Command Syntax ................................................................................................ 1432Base Command Set ............................................................................................. 1432NNTP Command Extensions ................................................................................. 1434
NNTP Status Responses and Response Codes ................................................................ 1438
86GOPHER PROTOCOL (GOPHER) 1443
Gopher Overview and General Operation ....................................................................1443Information Storage on Gopher Servers ................................................................. 1444Gopher Client/Server Operation ........................................................................... 1444
Important Differences Between Gopher and the Web ..................................................... 1445Gopher’s Role in the Modern Internet ........................................................................... 1445
PART II I -10INTERACTIVE AND ADMINISTRATIVE UTILITIES AND PROTOCOLS
87TCP/IP INTERACTIVE AND REMOTE APPLICATIONPROTOCOLS 1449
Telnet Protocol ........................................................................................................... 1450Telnet Overview, History, and Standards ................................................................ 1450Telnet Connections and Client/Server Operation ..................................................... 1453Telnet Communications Model and the Network Virtual Terminal (NVT) ..................... 1455Telnet Protocol Commands ................................................................................... 1458Telnet Interrupt Handling ...................................................................................... 1461Telnet Options and Option Negotiation ................................................................. 1462
Internet Relay Chat Protocol (IRC) ................................................................................. 1470IRC Communication Model and Client/Server Operation ......................................... 1471Messaging and IRC Channels ...............................................................................1471IRC and the Modern Internet ................................................................................. 1472
88TCP/IP ADMINISTRATION AND TROUBLESHOOTINGUTIL ITIES AND PROTOCOLS 1473
TCP/IP Host Name Utility (hostname) ............................................................................ 1474TCP/IP Communication Verification Utility (ping) ............................................................ 1475
Operation of the ping Utility ................................................................................. 1476Basic Use of ping ................................................................................................ 1476Methods of Diagnosing Connectivity Problems Using ping ........................................ 1477ping Options and Parameters ...............................................................................1478
TCP/IP Route Tracing Utility (traceroute) ........................................................................ 1479Operation of the traceroute Utility .......................................................................... 1480Basic Use of the traceroute Utility .......................................................................... 1481
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traceroute Options and Parameters ........................................................................ 1482TCP/IP Address Resolution Protocol Utility (arp) .............................................................. 1483TCP/IP DNS Name Resolution and Lookup Utilities (nslookup, host, and dig) ..................... 1484
TCP/IP DNS Registry Database Lookup Utility (whois/nicname) ....................................... 1489TCP/IP Network Status Utility (netstat) ........................................................................... 1491
The UNIX netstat Utility .........................................................................................1492The Windows netstat Utility .................................................................................. 1494
TCP/IP Configuration Utilities (ifconfig, ipconfig, and winipcfg) ....................................... 1496The ifconfig Utility for UNIX .................................................................................. 1496The ipconfig for Windows NT, 2000, and XP .........................................................1498The winipcfg Utility for Windows 95, 98, and Me .................................................. 1500
