Книга: Fedora™ Unleashed, 2008 edition

Networking with TCP/IP

Networking with TCP/IP

The basic building block for any network based on UNIX hosts is the Transport Control Protocol/Internet Protocol (TCP/IP) suite of three protocols. The suite consists of the Internet Protocol (IP), Transport Control Protocol (TCP), and Universal Datagram Protocol (UDP). IP is the base protocol. The TCP/IP suite is packet-based, which means that data is broken into little chunks on the transmit end for transmission to the receiving end. Breaking data up into manageable packets allows for faster and more accurate transfers. In TCP/IP, all data travels via IP packets, which is why addresses are referred to as IP addresses. It is the lowest level of the suite.

TCP is a connection-based protocol. Before data is transmitted between two machines, a connection is established between them. When a connection is made, a stream of data is sent to the IP to be broken into the packets that are then transmitted. At the receiving end, the packets are put back in order and sent to the proper application port. TCP/IP forms the basis of the Internet; without it, the Internet would be a very different place indeed, if it even existed!

On the other hand, UDP is a connectionless protocol. Applications using this protocol just choose their destination and start sending. UDP is normally used for small amounts of data or on fast and reliable networks. If you are interested in the internals of TCP/IP, see the "Reference" section at the end of this chapter for places to look for more information.

Fedora and Networking

Chances are that your network card was configured during the installation of Fedora. You can, however, use the ifconfig command at the shell prompt or Fedora's graphical network configuration tools, such as system-config-network, to edit your system's network device information or to add or remove network devices on your system. Hundreds of networking commands and utilities are included with Fedora — far too many to cover in this chapter and more than enough for coverage in two or three volumes.

Nearly all ethernet cards can be used with Linux, along with many PCMCIA wired and wireless network cards. The great news is that many USB wireless network devices also work just fine with Linux, and more will be supported with upcoming versions of the Linux kernel. Check the Linux USB Project at http://www.linux-usb.org/ for the latest developments or to verify support for your device.

After reading this chapter, you might want to learn more about other graphical network clients for use with Linux. The GNOME ethereal client, for example, can be used to monitor all traffic on your LAN or specific types of traffic. Another client, NmapFE, can be used to scan a specific host for open ports and other running services.

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