Teach Yourself TCP/IP in 14 Days Second Edition Preface to Second Edition About the Author Overview Introduction 1. Open Systems, Standards, and Protocols 2. TCP/IP and the Internet 3. The Internet Protocol (IP) 4. TCP and UDP 5. Gateway and Routing Protocols 6. Telnet and FTP 7. TCP/IP Configuration and Administration Basics 8. TCP/IP and Networks 9. Setting Up a Sample TCP/IP Network: Servers 10. Setting Up a Sample TCP/IP Network: DOS and Windows Clients 11. Domain Name Service 12. Network File System and Network Information Service 13. Managing and Troubleshooting TCP/IP 14. The Socket Programming Interface Appendix A: Acronyms and Abbreviations Appendix B: Glossary Appendix C: Commands Appendix D: Well-Known Port Numbers Appendix E: RFCs Appendix F: Answers to Quizzes This document was produced using a BETA version of HTML Transit 2 Teach Yourself TCP/IP in 14 Days, Second Edition The second edition of Teach Yourself TCP/IP in 14 Days expands on the very popular first edition, bringing the information up-to-date and adding new topics to complete the coverage of TCP/IP. The book has been reorganized to make reading and learning easier, as well as to provide a more logical approach to the subject. New material in this edition deals with installing, configuring, and testing a TCP/IP network of servers and clients. You will see how to easily set up UNIX, Linux, and Windows NT servers for all popular TCP/IP services, including Telnet, FTP, DNS, NIS, and NFS. On the client side, you will see how to set up DOS, Windows, Windows 95, and WinSock to interact with a server. Examples and tips throughout these sections make the process easy and clear. Also added in this edition of Teach Yourself TCP/IP in 14 Days are new sections on DNS, NFS, and NIS. These network services have become popular with the growth of large TCP/IP networks, so we show you how to configure and use them all. A new section on the latest version of IP updates the treatment of the base protocols to 1996 standards. Tim Parker Mail: Dean Miller Comments Department Sams Publishing 201 W. 103rd Street Indianapolis, IN 46290 ■ Topics Covered in Detail in this Edition ■ The TCP/IP Protocol Family ■ Transport ■ Routing ■ Network Addresses ■ User Services ■ Gateway Protocols ■ Others Topics Covered in Detail in this Edition ● Standards and terminology ● Network architecture ● History of TCP/IP and the Internet ● IPng (IP version 6) ● Telnet and FTP ● Configuring servers and clients Introduction So you've just been told you are on a TCP/IP network, you are the new TCP/IP system administrator, or you have to install a TCP/IP system. But you don't know very much about TCP/IP. That's where this book comes in. You don't need any programming skills, and familiarity with operating systems is assumed. Even if you've never touched a computer before, you should be able to follow the material. This book is intended for beginning through intermediate users and covers all the protocols involved in TCP/IP. Each protocol is examined in a fair level of detail to show how it works and how it interacts with the other protocols in the TCP/IP family. Along the way, this book shows you the basic tools required to install, configure, and maintain a TCP/IP network. It also shows you most of the user utilities that are available. Because of the complex nature of TCP/IP and the lack of a friendly user interface, there is a lot of information to look at. Throughout the book, the role of each protocol is shown separately, as is the way it works on networks of all sizes. The relationship with large internetworks (like the Internet) is also covered. Each chapter in the book adds to the complexity of the system, building on the material in the earlier chapters. Although some chapters seem to be unrelated to TCP/IP at first glance, all the material is involved in an integral manner with the TCP/IP protocol family. The last few chapters cover the installation and troubleshooting of a network. By the time you finish this book, you will understand the different components of a TCP/IP system, as well as the complex acronym-heavy jargon used. Following the examples presented, you should be able to install and configure a complete TCP/IP network for any operating system and hardware platform. The TCP/IP Protocol Family Transport Transmission Control Protocol (TCP): connection-based services User Datagram Protocol (UDP): connectionless services Routing Internet Protocol (IP): handles transmission of information Internet Control Message Protocol (ICMP): handles status messages for IP Routing Information Protocol (RIP): determines routing Open Shortest Path First (OSPF): alternate protocol for determining routing Network Addresses Address Resolution Protocol (ARP): determines addresses Domain Name System (DNS): determines addresses from machine names Reverse Address Resolution Protocol (RARP): - determines addresses User Services Boot Protocol (BOOTP): starts up a network machine File Transfer Protocol (FTP): transfers files Telnet: allows remote logins Gateway Protocols Exterior Gateway Protocol (EGP): transfers routing information for external networks Gateway-to-Gateway Protocol (GGP): transfers routing information between gateways Interior Gateway Protocol (IGP): transfers routing information for internal networks Others Network File System (NFS): enables directories on one machine to be mounted on another Network Information Service (NIS): maintains user accounts across networks Remote Procedure Call (RPC): enables remote applications to communicate Simple Mail Transfer Protocol (SMTP): transfers electronic mail Simple Network Management Protocol (SNMP): sends status messages about the network ■ The TCP/IP Protocol Family The TCP/IP Protocol Family Transport TCP (Transmission Control Protocol) Connection-based services (Day 4) UDP (User Datagram Protocol) Connectionless services (Day 4) Routing IP (Internet Protocol) Handles transmission of information (Day 3) ICMP (Internet Control Message Protocol) Handles status messages for IP (Day 3) RIP (Routing Information Protocol) Determines routing (Day 5) OSPF (Open Shortest Path First) Alternate protocol for determining routing (Day 5) Network Addresses ARP (Address Resolution Protocol) Determines addresses (Day 2) DNS (Domain Name System) Determines addresses from machine names (Day 2 and Day 11) RARP (Reverse Address Resolution Protocol) Determines addresses (Day 2) User Services BOOTP (Boot Protocol) Starts up a network machine (Day 11) FTP (File Transfer Protocol) Transfers files (Day 6) Telnet Enables remote logins (Day 6) TFTP (Trivial File Transfer Protocol) Enables remote file transfers (Day 6) Gateway Protocols EGP (Exterior Gateway Protocol) Transfers routing information for external networks (Day 3 and Day 5) GGP (Gateway-to-Gateway Protocol) Transfers routing information between gateways (Day 3 and Day 5) IGP (Interior Gateway Protocol) Transfers routing information for internal networks (Day 5) Others NFS (Network File System) Enables directories on one machine to be mounted on another (Day 12) NIS (Network Information Service) Maintains user accounts across networks (Day 12) NTP (Network Time Protocol) Synchronizes clocks (Day 11) PING (Packet Internet Groper) Checks connectivity (Day 7) RPC (Remote Procedure Call) Enables remote applications to communicate (Day 12) SNMP (Simple Network Management Protocol) Sends status messages about the network (Day 13) ■ Open Systems ■ What Is an Open System? ■ Network Architectures ■ Local Area Networks ■ The Bus Network ■ The Ring Network ■ The Hub Network ■ Wide Area Networks ■ Layers ■ The Application Layer ■ The Presentation Layer ■ The Session Layer ■ The Transport Layer ■ The Network Layer ■ The Data Link Layer ■ The Physical Layer ■ Terminology and Notations ■ Packets ■ Subsystems ■ Entities ■ N Notation ■ N-Functions ■ N-Facilities ■ Services ■ Making Sense of the Jargon ■ Queues and Connections ■ Standards ■ Setting Standards ■ Internet Standards ■ Protocols ■ Breaking Data Apart ■ Protocol Headers ■ Summary ■ Q&A ■ Quiz — 1 — Open Systems, Standards, and Protocols Today I start looking at the subject of TCP/IP by covering some background information you will need to put TCP/IP in perspective, and to understand why the TCP/IP protocols were designed the way they are. This chapter covers some important information, including the following: ● What an open system is ● How an open system handles networking ● Why standards are required ● How standards for protocols like TCP/IP are developed ● What a protocol is ● The OSI protocols You might be eager to get started with the nitty-gritty of the TCP/IP protocols, or to find out how to use the better-known services like FTP and Telnet. If you have a specific requirement to satisfy (such as how to transfer a file from one system to another), by all means use the Table of Contents to find the section you want. But if you want to really understand TCP/IP, you will need to wade through the material in this chapter. It's not complicated, although there are quite a few subjects to be covered. Luckily, none of it requires memorization; more often than not it is a matter of setting the stage for something else I discuss in the next week or so. So don't get too overwhelmed by this chapter! Open Systems This is a book about a family of protocols called TCP/IP, so why bother looking at open systems and standards at all? Primarily because TCP/IP grew out of the need to develop a standardized communications procedure that would inevitably be used on a variety of platforms. The need for a standard, and one that was readily available to anyone (hence open), was vitally important to TCP/IP's success. Therefore, a little background [...]... are combined into a single one for the layer above Multiplexing and splitting (and their reverses, demultiplexing and recombining) are different in the manner in which the lines are split With multiplexing, several connections combine into one in the layer below With splitting, however, one connection can be split into several in the layer below As you might expect, each has its importance within TCP... into a larger PDU within the layer in which the SDUs originated Unblocking is the breaking up of a PDU into several SDUs in the same layer Concatenation is the process of one layer combining several N-PDUs from the next higher layer into one SDU (like blocking except occurring across a layer boundary) Separation is the reverse of concatenation, so that a layer breaks a single SDU into several PDUs for... all aspects of the standard must be machine-independent Imagine trying to define a 2x4 without using a measurement you are familiar with, such as inches, or if inches are adopted, it would be difficult to define inches in an unambiguous way (which indeed is what happens, because most units of length are defined with respect to the wavelength of a particular kind of coherent light) Computers communicate... turned over the task of developing the Internet standards to the Internet Engineering Task Force (IETF), and the long-term research was assigned to the Internet Research Task Force (IRTF) The IAB retained final authorization over anything proposed by the two task forces The last step in this saga was the formation of the Internet Society in 1992, when the IAB was renamed the Internet Architecture Board... for existing and future standards, reporting to the board of the Internet Society After all that, what happened during the shuffling? Almost from the beginning, the Internet was defined as "a loosely organized international collaboration of autonomous, interconnected networks," which supported host-to-host communications "through voluntary adherence to open protocols and procedures" defined in a technical... ring network Despite the almost automatic assumption that a ring network has a backbone with the ends of the cable joined to form a loop, there is no real cabling ring at all The ring name derives from the construction of the central control unit The term ring is a misnomer because ring networks don't have an unending cable like a bus network with the two terminators joined together Instead, the ring... multiplexed into a single session connection) Demultiplexing is the reverse of multiplexing, in which one connection is split into several connections for the layer above it Splitting is when a single connection is supported by several connections in the layer below (so the data link layer might have three connections to support one network layer connection) Recombining is the reverse of splitting, so... together again with a jumper of some sort or the network might cease to function properly The Ring Network A ring network topology is often drawn as its name suggests, shaped like a ring A typical ring network schematic is shown in Figure 1.3 You might have heard of a token ring network before, which is a ring topology network You might be disappointed to find no physical ring architecture in a ring network,... well-defined process, shown schematically in Figure 1.10 It begins with a request for comment (RFC) This is usually a document containing a specific proposal, sometimes new and sometimes a modification of an existing standard RFCs are widely distributed, both on the network itself and to interested parties as printed documents Important RFCs and instructions for retrieving them are included in the appendixes... city All four LANs are joined together by high-speed telephone lines However, as far as the Internet and anyone outside the ABC Software company are concerned, the ABC Software WAN is a single entity (It has a single domain name for the Internet Don’t worry if you don’t known what a domain is at this point in time; it refers to a single entity for organizational purposes on the Internet, as you will see . produced using a BETA version of HTML Transit 2 Teach Yourself TCP/IP in 14 Days, Second Edition The second edition of Teach Yourself TCP/IP in 14 Days expands. machine-to-machine bus network is its simplicity. Adding new machines to the network means installing a network card and connecting the new machine into