System information

we felt that it might still be useful to some readers, so we’ve left it in the book as
an appendix.
Appendix B, Protocols for VoIP
Delves into all the particularities of Voice over IP. This was also a chapter in old
versions of this book.
Appendix C, Preparing a System for Asterisk
Contains information you should be aware of and take into consideration when
planning an Asterisk deployment.
Software
This book is focused on documenting Asterisk version 1.8; however, many of the con-
ventions and much of the information in this book is version-agnostic. Linux is the
operating system we have run and tested Asterisk on, and we have documented instal-
lation instructions for both CentOS (Red Hat Enterprise Linux–based) and Ubuntu
(Debian-based) where they differ from each other.
Conventions Used in This Book
The following typographical conventions are used in this book:
Italic
Indicates new terms, URLs, email addresses, filenames, file extensions, pathnames,
directories, and package names, as well as Unix utilities, commands, options,
parameters, and arguments.
Constant width
Used to display code samples, file contents, command-line interactions, library
names, and database commands.
Constant width bold
Indicates commands or other text that should be typed literally by the user. Also
used for emphasis in code.
Constant width italic
Shows text that should be replaced with user-supplied values.
[ Keywords and other stuff ]
Indicates optional keywords and arguments.
{ choice-1 | choice-2 }
Signifies either choice-1 or choice-2.
This icon signifies a tip, suggestion, or general note.
xxvi | Preface