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Lesson 4 Serial modems
Objective Define a modem's role in the Linux system.

Linux Serial Modems

A modem places calls to or receives calls from other computers over conventional telephone lines. When a call is established, the communicating computers negotiate a protocol. Linux supports serial protocols such as Xmodem, Zmodem , and Kermit, as well as Internet protocols such as PPP and SLIP. PPP enables other protocols, such as IP or IPX, to function over a telephone line. PPP provides a peer-to-peer connection and is the most common method of connecting to an Internet Service Provider (ISP).
As illustrated below, the client computer uses its modem to establish a connection to the server computer at your ISP. The client computer must have a properly configured kernel, meaning PPP or SLIP support is available to the kernel. PPP support is modularized and included with Red Hat Linux.
  1. 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.
  2. Xmodem: Xmodem is a popular file-transfer protocol.
  3. Zmodem: Zmodem is similar, but has improved error detection.
  4. Kermit: A communications protocol developed at Columbia University.
  5. PPP: Point-to-Point Protocol. It is used to connect computers with the Internet.
  6. SLIP: Serial Line Internet Protocol. SLIP is very similar to PPP.
  7. IPX: Internetwork Packet Exchange protocol. IPX is a networking protocol.

Connecting with a serial modem
More information about how to configure a PPP dial-up connection is included in the Linux Documentation Project (LDP) PPP-HOWTO, available from the Resources page. You can also find additional information in The Official Red Hat Linux Installation Guide. The next lesson discusses uses for multiple network interface cards.
Click the link below to read about the setserial command to query the characteristics of a serial device.
Set Serial Command