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TCP/IP and Data Communications Administration Guide

Protocol Definitions in the Devices File

You can define the protocol to use with each device in /etc/uucp/Devices. This is usually unnecessary because you can use the default or define the protocol with the particular system you are calling. (Refer to "/etc/uucp/Systems File".) If you do specify the protocol, you must use the form:

Type,Protocol [parameters]

For example, you can use TCP,te to specify the TCP/IP protocol.

Table 12-4 shows the available protocols for the Devices file:

Table 12-4 Protocols Used in /etc/uucp/Devices

Protocol 

Description 

t

This protocol is commonly used for transmissions over TCP/IP and other reliable connections. It assumes error-free transmissions.  

g

This is UUCP's native protocol. It is slow, reliable, and good for transmission over noisy telephone lines.  

e

This protocol assumes transmission over error-free channels that are message-oriented (as opposed to byte-stream-oriented, like TCP/IP).  

f

This protocol is used for transmission over X.25 connections. It relies on flow control of the data stream, and is meant for working over links that can (almost) be guaranteed to be error-free, specifically X.25/PAD links. A checksum is carried out over a whole file only. If a transport fails, the receiver can request retransmission(s).  

Here is an example showing a protocol designation for a device entry: 


TCP,te - - Any TCP -

This example indicates that, for device TCP, try to use the t protocol. If the other end refuses, use the e protocol.

Neither e nor t is appropriate for use over modems. Even if the modem assures error-free transmission, data can still be dropped between the modem and the CPU.