Lesson 8

Linux supports communication with other computers over telephone lines and networks. Serial devices, such as internal and external modems, and non-serial devices, such as network interface cards, actually move the data from computer to computer. The Linux kernel supports these devices either automatically or via loaded modules.
The setserial command configures and queries serial device characteristics. This program provides a single manipulative interface for a vast range of serial devices, including modems, mice, and serial terminals.
The getty program and its variants support serial communications under Linux. Commonly used protocols over serial lines include PPP and SLIP, which Red Hat Linux provides pre-configured; the end user simply needs to fill in particular configuration details.
Multiple network interface cards (NIC) allow communication across different networks. The Network Configurator provides an interface for setting up NIC characteristics, such as device, address, gateway, and so on. With multiple network cards configured, a Linux computer can act as a router, bridge, or firewall.

Having completed this module, you should be able to:

1. Describe some of the serial devices supported by Red Hat Linux
2. Configure and use serial ports
3. Define a modem's role in a Linux system
4. Describe the rationale for using multiple network interface cards
5. Load the correct NIC modules into the kernel to enable multiple network interface cards
6. Use the Network Configurator tool to enable multiple network interface cards

This module introduced you to the following terms:

1. BIOS: Basic Input and Output System. The BIOS is responsible for providing a standard interface to the computer hardware. An operating system writes to a particular BIOS specification, rather than worrying about the details for all supported hardware.
2. Bridging: Bridges isolate segments of the same network to cut down on overall network traffic.
3. Daemon: A daemon is a program that waits for a request from another program. The daemon then performs the desired action, such as creating an http session, or opening and maintaining a communications socket. Some common daemons include httpd, telnetd, and ftpd.
4. Firewalling: Firewalling protects one network from another. A computer acting as a firewall filters, logs, and audits traffic flowing from one network into the other.
5. IP: Internet Protocol. Usually combined with TCP (Transmission Control Protocol) in order to pass data between a destination and source.
6. Kermit: A communications protocol developed at Columbia University.
7. Modem: A device that allows computers to send data over conventional analong phone lines.
8. PPP: Point-to-Point Protocol. It is used to connect computers with the Internet.
9. Protocol: Protocols identify the type of content communicated. One of the most common protocols is PPP, for communication to and from an Internet Service Provider.
10. Routing: The process of moving information from one network to another. It is very similar to bridging; however, routing works on the network layer.
11. Serial port: A serial port or interface that can be used for serial communication so that one bit of data is transmitted at a time.
12. SLIP: Serial Line Internet Protocol. SLIP is very similar to PPP.
13. Xmodem: Xmodem is a popular file-transfer protocol.
14. Zmodem: Zmodem is similar, but has improved error detection.

Read about what other people are thinking about the use of serial and networking devices with the Linux OS.

Before moving on to the next module, click the Quiz link below to test your understanding of enabling serial and non-serial communications.
Serial Communication - Quiz