Internetworking With TCP/IP

Transcription

1 Internetworking With TCP/IP Vol II: Design, Implementation, and Internals SECOND EDITION DOUGLAS E. COMER and DAVID L. STEVENS Department of Computer Sciences Purdue University West Lafayette, IN Prentice-Hall International, Inc.

2 Contents Foreword Preface Chapter 1 Introduction And Overview 1.1 TCP/IP Protocols The Need To Understand Details Complexity Of Interactions Among Protocols The Approach In This Text The Importance Of Studying Code 3 /.6 The Xinu Operating System Organization Of The Remainder Of The Book 4 /.8 Summary 4 Chapter 2 The Structure Of TCP/IP Software In An Operating System 2.1 Introduction The Process Concept Process Priority Communicating Processes Interprocess Communication Device Drivers, Input, And Output Network Input and Interrupts Passing Packets To Higher Level Protocols Passing Datagrams From IP To Transport Protocols Delivery To Application Programs Information Flow On Output From TCP Through IP To Network Output 20

3 2.13 UDP Output Summary 21 Chapter 3 Network Interface Layer 3.1 Introduction The Network Interface Abstraction Logical State Of An Interface Local Host Interface Buffer Management Demultiplexing Incoming Packets Summary 36 Chapter 4 Address Discovery And Binding (ARP) 4.1 Introduction Conceptual Organization Of ARP Software Example ARP Design Data Structures For The ARP Cache ARP Output Processing AA 4.6 ARP Input Processing ARP Cache Management ARP Initialization ARP Configuration Parameters Summary 59 Chapter 5 IP: Global Software Organization 5.1 Introduction The Central Switch IP Software Design IP Software Organization And Datagram Flow 5.5 Byte-Ordering In The IP Header Sending A Datagram To IP Table Maintenance Summary 82

4 Contents ix Chapter 6 IP: Routing Table And Routing Algorithm Introduction Route Maintenance And Lookup Routing Table Organization Routing Table Data Structures Origin Of Routes And Persistence Routing A Datagram Periodic Route Table Maintenance IP Options Processing Summary 105 Chapter 7 IP: Fragmentation And Reassembly Introduction Fragmenting Datagrams Implementation Of Fragmentation Datagram Reassembly Maintenance Of Fragment Lists Initialization Summary 124 Chapter 8 IP: Error Processing (ICMP) Introduction ICMP Message Formats Implementation Of ICMP Messages Handling Incoming ICMP Messages Handling An ICMP Redirect Message Setting A Subnet Mask Choosing A Source Address For An ICMP Packet Generating ICMP Error Messages Avoiding Errors About Errors Allocating A Buffer For ICMP The Data Portion Of An ICMP Message Generating An ICMP Redirect Message / 3 Summary 145

5 Chapter 9 IP: Multicast Processing (IGMP) 9.1 Introduction Maintaining Multicast Group Membership Information A Host Group Table Searching For A Host Group Adding A Host Group Entry To The Table Configuring The Network Interface For A Multicast Address Translation Between IP and Hardware Multicast Addresses Removing A Multicast Address From The Host Group Table Joining A Host Group Maintaining Contact With A Multicast Router Implementing IGMP Membership Reports Computing A Random Delay A Process To Send IGMP Reports Handling Incoming IGMP Messages Leaving A Host Group Initialization Of IGMP Data Structures Summary 168 Chapter 10 UDP: User Datagrams 70.7 Introduction UDP Ports And Demultiplexing J UDP UDP Output Processing Summary 188 Chapter 11 TCP: Data Structures And Input Processing 77.7 Introduction Overview Of TCP Software J Transmission Control Blocks TCP Segment Format Sequence Space Comparison TCP Finite State Machine Example State Transition Declaration Of The Finite State Machine TCB Allocation And Initialization Implementation Of The Finite State Machine Handling An Input Segment 205

6 Contents XI Summary 214 Chapter 12 TCP: Finite State Machine Implementation Introduction CLOSED State Processing Graceful Shutdown Timed Delay After Closing TIME-WAIT State Processing CLOSING State Processing FIN-WAIT-2 State Processing FIN-WAIT-1 State Processing CLOSE-WAIT State Processing LAST-ACK State Processing ESTABLISHED State Processing Processing Urgent Data In A Segment Processing Other Data In A Segment Keeping Track Of Received Octets Aborting A TCP Connection Establishing A TCP Connection Initializing A TCB SYN-SENT State Processing SYN-RECEIVED State Processing LISTEN State Processing Initializing Window Variables For A New TCB Summary 246 Chapter 13 TCP: Output Processing / Introduction Controlling TCP Output Complexity «Four TCP Output States 248 /5.4 TCP Output As A Process TCP CtapMf Messages Encoding Output States And TCB Numbers Implementation Of The TCP Output Process Mutual Exclusion Implementation Of The IDLE State Implementation Of The PERSIST State Implementation Of The TRANSMIT State Implementation Of The RETRANSMIT State Sending A Segment 255

7 Xll Contents Computing The TCP Data Length Computing Sequence Counts Other TCP Procedures Summary 267 Chapter 14 TCP: Timer Management Introduction A General Data Structure For Timed Events A Data Structure For TCP Events Timers, Events, And Messages The TCP Timer Process Deleting A TCP Timer Event 21A 14.7 Deleting All Events For A TCB Determining The Time Remaining For An Event Inserting A TCP Timer Event Starting TCP Output Without Delay Summary 280 Chapter 15 TCP: Flow Control And Adaptive Retransmission Introduction The Difficulties With Adaptive Retransmission J Tuning Adaptive Retransmission Retransmission Timer And Backoff Window-Based Flow Control Maximum Segment Size Computation Congestion Avoidance And Control Slow-Start And Congestion Avoidance Round Trip Estimation And Timeout Miscellaneous Notes And Techniques Summary 306 Chapter 16 TCP: Urgent Data Processing And The Push Function Introduction Out-Of-Band Signaling J Urgent Data Interpreting The Standard Configuration For Berkeley Urgent Pointer Interpretation Informing An Application 313

8 Contents Xlll 16.7 Reading Data From TCP Sending Urgent Data TCP Push Function Interpreting Push With Out-Of-Order Delivery Implementation Of Push On Input Summary 320 Chapter 17 Socket-Level Interface Introduction Interfacing Through A Device TCP Connections As Devices An Example TCP Client Program An Example TCP Server Program Implementation Of The TCP Master Device Implementation Of A TCP Slave Device Initialization Of A Slave Device Summary 352 Chapter 18 RIP: Active Route Propagation And Passive Acquisition Introduction Acrive An<7 Passive Mode Participants J ßav/c RIP Algorithm And Cost Metric Instabilities And Solutions Message Types Protocol Characterization Implementation Of RIP z<? Principle RIP Process Responding To An Incoming Request Generating Update Messages Initializing Copies Of An Update Message Generating Periodic RIP Output Limitations Of RIP Summary 379 Chapter 19 OSPF: Route Propagation With An SPF Algorithm Introduction OSPF Configuration And Options J OSPF's Graph-Theoretic Model 382

9 XIV Contents 19.4 OSPF Declarations Adjacency And Link State Propagation Discovering Neighboring Gateways With Hello Sending Hello Packets Designated Router Concept Electing A Designated Router Reforming Adjacencies After A Change Handling Arriving Hello Packets Adding A Gateway To The Neighbor List Neighbor State Transitions OSPF Timer Events And Retransmissions Determining Whether Adjacency Is Permitted Handling OSPF input Declarations And Procedures For Link State Processing Generating Database Description Packets Creating A Template ATI Transmitting A Database Description Packet Handling An Arriving Database Description Packet Handling Link State Request Packets Building A Link State Summary OSPF Utility Procedures Summary 439 Chapter 20 SNMP: MIB Variables, Representations, And Bindings Introduction Server Organization And Name Mapping MIB Variables MIB Variable Names AAA 20.5 Lexicographic Ordering Among Names Prefix Removal Operations Applied To MIB Variables Names For Tables Conceptual Threading Of The Name Hierarchy Data Structure For MIB Variables A Data Structure For Fast Lookup Implementation Of The Hash Table Specification Of MIB Bindings Internal Variables Used In Bindings Hash Table Lookup SNMP Structures And Constants ASN.1 Representation Manipulation Summary A1A

10 Contents xv Chapter 21 SNMP: Client And Server Introduction All 21.2 Data Representation In The Server All 21.3 Server Implementation AIS 21.4 Parsing An SNMP Message Converting ASN.l Names In The Binding List Resolving A Query Interpreting The Get-Next Operation Indirect Application Of Operations Indirection For Tables Generating A Reply Message Backward Converting From Internal Form to ASN.l Utility Functions Used By The Server Implementation Of An SNMP Client Initialization Of Variables Summary 500 Chapter 22 SNMP: Table Access Functions Introduction Table Access Object Identifiers For Tables Address Entry Table Functions Address Translation Table Functions Network Interface Table Functions Routing Table Functions TCP Connection Table Functions Summary 545 Chapter 23 Implementation In Retrospect Introduction Statistical Analysis Of The Code Lines Of Code For Each Protocol Functions And Procedures For Each Protocol Summary 551

11 xvi Contents Appendix 1 Cross Reference Of Procedure Calls 553 Appendix 2 Xinu Functions And Constants Used In The Code 573 Bibliography 589 Index 597