LAPB configuration

Introduction

LAPB configuration is the process of defining the protocol parameters for LAPB links. Although most LAPB protocol parameters can safely be left as default values, some values have to be changed for every installation.

You must run x25config or wanware stop; wanware start to have the new configuration take effect.

Configuration File Location

Link configuration files used by Wanware are found in the /usr/lib/x25/config/ directory.

File Structure

LAPB configuration files are ASCII text, and can be modified with any text editor. The files may contain blank lines, and the conversion program ignores all text that follows a "#" character. Only one parameter can occur on a line, and a parameter keyword must always be separated from the parameter value.

Parameters and their values are separated by either a space or =. For example:

linkenable YES
linkenable=YES

There are default values for every parameter. You can look at the default values in /usr/lib/x25/config/net.defaults. Changing this file does not affect the defaults. If a parameter in the configuration file you specify is not present, the default is silently supplied.

Things to remember when creating link configuration files:

Parameter order doesn't matter. If you duplicate a parameter, the last value is used.
Separate parameter names from their values by a space or =.
The parser is case-sensitive, so specify YES and NO in upper case only.
Any lines beginning with # are ignored, as are the contents of a line beyond the first #.
Changing net.defaults has no effect. This file is included for you to view the defaults which are built into the configuration utilities.

When you are creating a link parameter file, you only need to specify parameters that differ from the default ones. Therefore, you can set up a link with the exact characteristics described in net.defaults by specifying the name of an empty file.

net.defaults contains comments which describe each item in the file, so you can use it for reference when you create your own link configuration (or modify one of the supplied files). If there is any difference between the following descriptions and the file itself, follow what is in the file as it is more current.

Changing Link Startup Behaviour

If the data network to which you are connecting is not one of those specified for the netid parameter, you may find that the LAPB link does not start up properly. If you need to change the way the HDLC (LAPB) protocol is started, experiment by changing netid, then restarting the protocol. LAPB Troubleshooting explains how to determine the state of the HDLC link, while LAPB Configuration Parameters contains information on the various protocol options associated with different netid values.

Revision 6.3.0 (April 2004)