Asterisk: The Future of Telephony

Appendix A. VoIP Channels

VoIP channels in Asterisk represent connections to the protocols they support. Each protocol you wish to use requires a configuration file, containing general parameters defining how your system handles the protocol as well as specific parameters for each channel (or device) you will want to reference in your dialplan. In this appendix, we’ll take an in-depth look at the IAX and SIP configuration files.

IAX

The IAX configuration file (iax.conf) contains all of the configuration information Asterisk needs to create and manage IAX protocol channels. The sections in the file are separated by headings, which are formed by a word framed in square brackets ([]). The name in the brackets will be the name of the channel, with one notable exception: the [general] section, which is not a channel, is the area where global protocol parameters are defined.

This section examines the various general and channel-specific settings for iax.conf. We will define each parameter, and then give an example of its use. Certain options may have several valid arguments. These arguments are listed beside the option, separated with the pipe symbol (|). For example, bandwidth=low|medium|high means that the bandwidth option accepts one of the values low, medium, or high as its argument.

You can insert comments anywhere in the iax.conf file, by preceding the comment text with the semicolon character (;). Everything to the right of the semicolon will be ignored. Feel free to use comments liberally. ...