The ABCs of TCP IP

344 Pages·2002·10.04 MB·English

by  Gilbert Held

The ABCs
of
TCP/IP
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The ABCs
of
TCP/IP
GILBERT HELD
AUERBACH PUBLICATIONS
A CRC Press Company
Boca Raton London New York Washington, D.C.
AU1463/frame/fm Page iv Tuesday, September 10, 2002 9:18 AM
Library of Congress Cataloging-in-Publication Data
Held, Gilbert, 1943-
The ABCs of TCP/IP / Gilbert Held.
p. cm.
Includes index.
ISBN 0-8493-1463-1
1. TCP/IP (Computer network protocol) I. Title.
TK5105.585 .H44695 2002
004.6′2—dc21 2002028013
CIP
This book contains information obtained from authentic and highly regarded sources. Reprinted
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© 2003 by CRC Press LLC
Auerbach is an imprint of CRC Press LLC
No claim to original U.S. Government works
International Standard Book Number 0-8493-1463-1
Library of Congress Card Number 2002028013
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
Printed on acid-free paper
AU1463/frame/fm Page v Tuesday, September 10, 2002 9:18 AM
Contents
Chapter 1 Overview .....................................................................................1
Applications............................................................................................................. 2
Current Applications........................................................................................ 2
Electronic Mail .................................................................................................2
File Transfers ....................................................................................................4
Remote Terminal Access .................................................................................7
Web Surfing ......................................................................................................7
Emerging Applications ...................................................................................10
Audio and Video Players ..............................................................................10
Voice-over-IP ..................................................................................................11
Virtual Private Networking ............................................................................14
Book Preview ........................................................................................................14
The Protocol Suite .........................................................................................15
The Standards Process ...................................................................................15
The Internet Protocol and Related Protocols.............................................. 16
Transport Layer Protocols.............................................................................. 16
Applications and Built-In Diagnostic Tools................................................. 16
Routing ............................................................................................................17
Security Threats ..............................................................................................17
Enhancing Security ........................................................................................17
Emerging Technologies.................................................................................. 17
Chapter 2 The Protocol Suite ...................................................................19
The ISO Reference Model ....................................................................................19
OSI Reference Model Layers......................................................................... 20
Layer 1: The Physical Layer ...................................................................20
Layer 2: The Data-Link Layer................................................................. 21
Layer 3: The Network Layer ..................................................................22
Layer 4: The Transport Layer................................................................. 22
Layer 5: The Session Layer ....................................................................23
Layer 6: The Presentation Layer............................................................. 23
Layer 7: The Application Layer.............................................................. 23
v
AU1463/frame/fm Page vi Tuesday, September 10, 2002 9:18 AM
vi The ABCs of TCP/IP
Data Flow .......................................................................................................24
The TCP/IP Protocol Suite................................................................................... 24
The Network Layer ........................................................................................24
IP ..............................................................................................................25
ARP........................................................................................................... 25
ICMP......................................................................................................... 26
The Transport Layer....................................................................................... 26
TCP ...........................................................................................................26
UDP.......................................................................................................... 27
The Application Layer ...................................................................................27
Data Flow and Header Utilization................................................................ 27
Chapter 3 Internet Governing Bodies and the Standards
Process........................................................................................ 31
Internet Governing Bodies ...................................................................................31
Internet Evolution........................................................................................... 32
The IAB and IETF.......................................................................................... 33
The IANA........................................................................................................ 34
Request for Comments.......................................................................................... 34
The Standards Process................................................................................... 35
Draft RFC.................................................................................................. 35
Proposed Standard and Draft Standard................................................. 35
RFC Standard........................................................................................... 35
RFC Details..................................................................................................... 36
RFC Categories......................................................................................... 36
Accessing RFCs............................................................................................... 36
Best Current Practice...................................................................................... 42
Chapter 4 The Internet Protocol and Related Protocols ....................43
The Internet Protocol ...........................................................................................44
Datagrams and Segments ..............................................................................44
Datagrams and Datagram Transmission .......................................................44
Routing ........................................................................................................... 45
The IP Header................................................................................................ 45
Bytes versus Octets................................................................................. 45
Vers Field .................................................................................................46
Hlen Field................................................................................................ 46
Service Type Field................................................................................... 47
Total Length Field ...................................................................................48
Identification and Fragment Offset Fields............................................. 48
Flags Field................................................................................................ 50
Time to Live Field ..................................................................................51
Protocol Field ..........................................................................................51
Header Checksum Field .........................................................................54
Source and Destination Address Fields................................................. 55
Options ....................................................................................................55
End of Option List ..................................................................................56
No Operation........................................................................................... 56
Security..................................................................................................... 56
Loose Source Routing .............................................................................56
AU1463/frame/fm Page vii Tuesday, September 10, 2002 9:18 AM
Contents vii
Record Route........................................................................................... 57
Stream ID .................................................................................................57
Strict Source Routing ..............................................................................57
IP Addressing ........................................................................................................57
Overview......................................................................................................... 58
The IP Addressing Scheme ...........................................................................59
Address Changes..................................................................................... 59
Rationale ..................................................................................................60
Overview .................................................................................................61
Class A Addresses.......................................................................................... 62
Loopback.................................................................................................. 63
Class B Addresses.......................................................................................... 63
Class C Addresses.......................................................................................... 65
Class D Addresses.......................................................................................... 65
Unicast, Broadcast, and Multicast Comparison ....................................66
Class E Addresses........................................................................................... 67
Dotted Decimal Notation............................................................................... 68
Basic Workstation Configuration................................................................... 69
Reserved Addresses........................................................................................ 73
The WINIPCFG Utility.................................................................................... 74
Subnetting....................................................................................................... 76
Overview.................................................................................................. 76
Subnetting Example................................................................................. 76
Host Restrictions .....................................................................................78
The Zero Subnet .....................................................................................78
Internal versus External Subnet Viewing.............................................. 79
Using the Subnet Mask........................................................................... 80
Multiple Interface Addresses......................................................................... 82
Address Resolution................................................................................................ 84
Ethernet and Token Ring Frame Formats.................................................... 84
LAN Delivery.................................................................................................. 85
Address Resolution Operation....................................................................... 85
ARP Packet Fields.................................................................................... 85
Locating the Required Address ..............................................................86
Gratuitous ARP........................................................................................ 87
Proxy ARP........................................................................................................87
RARP.................................................................................................................87
ICMP........................................................................................................................88
Overview......................................................................................................... 88
The ICMP Type Field..................................................................................... 89
The ICMP Code Field ....................................................................................89
Examining Message Types and Code Field Values ....................................90
Echo Reply............................................................................................... 92
Destination Unreachable......................................................................... 92
Network Unreachable....................................................................... 92
Host Unreachable............................................................................. 92
Protocol Unreachable........................................................................93
Port Unreachable...............................................................................93
Fragmentation Needed and Don’t Fragment Was Set................... 93
Source Route Failed..........................................................................93
AU1463/frame/fm Page viii Tuesday, September 10, 2002 9:18 AM
viii The ABCs of TCP/IP
Destination Network Unknown....................................................... 93
Source Host Isolated ........................................................................93
Destination Network Is Administratively Prohibited...................... 93
Destination Host Is Administratively Prohibited............................ 94
Destination Network Unreachable for Type of Service.................94
Destination Host Unreachable for Type of Service........................94
Communications Administratively Prohibited..................................94
Host Precedence Violation................................................................94
Precedence Cutoff in Effect............................................................. 94
Source Quench........................................................................................ 94
Redirect......................................................................................................95
Echo...........................................................................................................95
Time Exceeded........................................................................................ 95
Router Advertisement and Solicitation................................................... 95
Parameter Problem...................................................................................95
Timestamp and Timestamp Reply...........................................................96
Information Request and Information Reply.........................................96
Address Mask Request and Reply...........................................................96
Traceback..................................................................................................97
ICMP Vulnerabilities....................................................................................... 97
Chapter 5 The Transport Layer.............................................................. 99
TCP .........................................................................................................................99
The TCP Header........................................................................................... 100
Source and Destination Port Fields ............................................................100
Multiplexing and Demultiplexing......................................................... 101
Port Numbers ........................................................................................102
Well-Known Ports.................................................................................. 105
Registered Ports..................................................................................... 105
Dynamic or Private Ports...................................................................... 107
Sequence and Acknowledgment Number Fields....................................... 107
Hlen Field..................................................................................................... 108
Code Bits Field..............................................................................................108
URG Bit.................................................................................................. 108
ACK Bit................................................................................................... 109
PSH Bit................................................................................................... 109
RST Bit.................................................................................................... 109
SYN Bit................................................................................................... 109
FIN Bit.................................................................................................... 109
Window Field............................................................................................... 109
Checksum Field............................................................................................ 110
Urgent Pointer Field ....................................................................................110
Options......................................................................................................... 111
Padding Field ...............................................................................................112
Connection Establishment............................................................................ 112
Connection Function Calls ..........................................................................112
Port Hiding............................................................................................. 112
Passive OPEN........................................................................................ 113
Active OPEN...........................................................................................113
The Three-Way Handshake .........................................................................114
AU1463/frame/fm Page ix Tuesday, September 10, 2002 9:18 AM
Contents ix
Overview................................................................................................ 114
Operation................................................................................................114
The TCP Window..........................................................................................116
Avoiding Congestion..............................................................................117
TCP Slow Start....................................................................................... 117
The Slow Start Threshold .....................................................................118
TCP Retransmissions............................................................................. 118
Keep-Alives............................................................................................ 119
Session Termination.............................................................................. 119
TCP Timers ...................................................................................................120
Delayed ACK Timer.............................................................................. 120
Keep-Alive Timer................................................................................... 120
Persist Timer ..........................................................................................121
FIN-WAIT-2 Timer .................................................................................121
UDP ......................................................................................................................121
The UDP Header .........................................................................................121
Source and Destination Port Fields..................................................... 122
Length Field ...........................................................................................122
Checksum Field..................................................................................... 122
Operation ......................................................................................................123
Applications.................................................................................................. 123
Chapter 6 Applications and Built-in Diagnostic Tools .......................125
The DNS................................................................................................................125
Purpose .........................................................................................................126
The Domain Name Structure...................................................................... 126
The Domain Name Tree........................................................................127
Zones and Zone Transfers.....................................................................128
The Name Resolution Process.................................................................... 129
Data Flow................................................................................................130
Message Format......................................................................................132
Identification Field.......................................................................... 132
Flags Field....................................................................................... 133
Number of Questions Field........................................................... 133
Number of Answers Field.............................................................. 134
Answers, Authority, and Additional Information Fields.............. 134
Question Field Composition ................................................................134
Answers Field Composition.................................................................. 134
Time Consideration............................................................................... 135
DNS Records................................................................................................. 135
The SOA Record ...................................................................................136
Checking Records.................................................................................. 137
Diagnostic Tools.................................................................................................. 137
Ping.................................................................................................................137
Operation................................................................................................138
Implementation.......................................................................................138
Using Windows NT Ping...................................................................... 139
Resolution Time Considerations............................................................140
Applications............................................................................................141
Traceroute......................................................................................................141