Mac OS X Unleashed

By John Ray and William C. Ray

• Table of Contents
  • Copyright
  • About the Author
  • Acknowledgments
  • Tell Us What You Think!
  • Introduction
  • Part I: Introduction to Mac OS X
  • Chapter 1. Mac OS X Component Architecture
  • Chapter 2. Installing Mac OS X
  • Chapter 3. Mac OS X Basics
  • Chapter 4. The Finder: Working with Files and Applications
  • Chapter 5. Running Classic Mac OS Applications
  • Part II: Inside Mac OS X
  • Chapter 6. Native Utilities and Applications
  • Chapter 7. Internet Communications
  • Chapter 8. Installing Third-Party Applications
  • Part III: User-Level OS X Configuration
  • Chapter 9. Network Setup
    • TCP/IP
    • The Network Control Pane
    • AppleTalk
    • Managing Locations
    • Testing Network Settings
    • Summary
  • Chapter 10. Printer and Font Management
  • Chapter 11. Additional System Components
  • Part IV: Introduction to BSD Applications
  • Chapter 12. Introducing the BSD Subsystem
  • Chapter 13. Common Unix Shell Commands: File Operations
  • Part V: Advanced Command-Line Concepts
  • Chapter 14. Advanced Shell Concepts and Commands
  • Chapter 15. Command-Line Applications and Application Suites
  • Chapter 16. Command-Line Software Installation
  • Chapter 17. Troubleshooting Software Installs, and Compiling and Debugging Manually
  • Chapter 18. Advanced Unix Shell Use: Configuration and Programming (Shell Scripting)
  • Part VI: Server/Network Administration
  • Chapter 19. X Window System Applications
  • Chapter 20. Command-Line Configuration and Administration
  • Chapter 21. AppleScript
  • Chapter 22. Perl Scripting and SQL Connectivity
  • Chapter 23. File and Resource Sharing with NetInfo
  • Chapter 24. User Management and Machine Clustering
  • Chapter 25. FTP Serving
  • Chapter 26. Remote Access and Administration
  • Chapter 27. Web Serving
  • Part VII: Server Health
  • Chapter 28. Web Programming
  • Chapter 29. Creating a Mail Server
  • Chapter 30. Accessing and Serving a Windows Network
  • Chapter 31. Server Security and Advanced Network Configuration
  • Chapter 32. System Maintenance
  • Appendix A. Command-Line Reference
  • Appendix B. Administration Reference

TCP/IP

TCP/IP, the acronym that has become a de facto name for a network communication protocol, stands for Transmission Control Protocol/Internet Protocol. TCP/IP has become so ubiquitous that many think of it, not just as a communications protocol, but as the only network communications protocol. Although not the only protocol out there (AppleTalk, covered later in this chapter is one of the others), TCP/IP has proven flexible enough to support different types of data with a large range of requirements for delivery, timing, and reliability.

Basically, the TCP/IP protocol can be thought of as specifying the manner in which pieces of data should be transferred between two machines. This protocol includes the notion that the transmission of data can be broken down into a number of separate and abstract layers. Figure 9.1 shows the TCP/IP protocol stack, the conceptual breakdown of the protocol into layers. This is commonly referred to as the OSI (Open Systems Interconnect) model of networking. As the functions of the layers are conceptually separate, the manner that the function of any layer is accomplished does not matter, as long as it cooperates with the layers above and below it in the manners that they expect.

Figure 9.1 The OSI network model, on which the TCP/IP stack is built.

For example, it doesn't matter whether the physical layer is carried by twisted-pair Ethernet cabling, radio waves, or even with data written on slips of paper and handed back-and-forth between people sitting at terminals. As long as the data transmitted by the Physical layer gets retrieved from or inserted into data structures correctly at the Data Link layer, the rest of the TCP/IP stack will function identically.

This separation of functionality into independent and abstract pieces is typical of Unix technologies, and allows the TCP/IP protocol to handle the transmission of a wide range of data types. Whether the data is equipment control where real-time transmission is critically important, or financial transactions where security and error-free transmissions are more important than speed, it is likely that the data can be fit into the TCP/IP model.

Going forward in the chapter, there are several TCP/IP-related terms you should be familiar with. These items define your connection to the Internet:

• IP Address— The address that uniquely identifies your computer on the Internet. An IP address is typically represented in the form ###.###.###.###, such as 192.168.0.1. An IP address is assigned either by your network administrator, or automatically via a DHCP or BOOTP server.
• Hostname— Typically, a hostname simply refers to the network name of your computer. Some people might use the term hostname to refer to the FQDN (fully qualified domain name) as well. This is the entire Internet name of your machine as registered with a DNS server, such as www.poisontooth.com.
• Subnet Mask— Similar in appearance to an IP address, a subnet mask tells your computer which part of the IP address identifies the network it is on, and which is the individual computer. Most users will be part of a class C network with the subnet mask 255.255.255.0. The last segment of the IP address identifies the computer, whereas the first three segments identify the network.
• Gateway/Router Address— The gateway address is an IP address of a network device that connects your local network to the rest of the Internet. A gateway handles any necessary translation between different types of networking media.
• DNS — Domain name servers are Internet servers that provide translation between IP addresses and fully qualified domain names. Each request for a machine using its FQDN requires an interaction with a DNS before a connection can take place.
• Network Interface— The device that connects your computer to the network. This can be an Ethernet port, AirPort card, and so on. Some computers might have multiple network interfaces. Mac OS X names its interfaces sequentially. The en0 interface is built-in Ethernet, and en1 is typically AirPort.

Using these pieces of information, you can configure your computer to access the Internet. Although most dial-in accounts automatically set these parameters for you, users connecting directly to a network via Ethernet or AirPort will need to know the appropriate settings for their network in order to continue.

If you'd like more information on the TCP/IP protocol and its use, I recommend Special Edition Using TCP/IP (ISBN: 0789718979).

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