Conventions

Most definitions are given upon first encountering a new term . There's a glossary included in case you miss a definition or just need a refresher.

Carrier is a word that is referred to in many different ways throughout the book. Sometimes it means a phone company, other times it refers to a data link system. Wherever a word has two potential meanings, the context should tell you which meaning is appropriate.

In most cases, examples are provided in terms of North American standards and practices. Where appropriate, European or Asian equivalents are mentioned.

Kilobit is abbreviated as k , while kilobits per second shows up as kbps . The same convention is used for mega- and giga- prefixes where applicable . For the sake of clarity, many authors will define whether kilo means 1,000 or 1,024. This is an important distinction, but you don't need to worry much about it here. It's safe to assume a multiple of 1,000 when kilo is used. That is, 64 kilo bits is exactly 64,000 bits and so on.

The following typographical conventions are used in this book:

Plain text

Indicates menu titles, menu options, menu buttons , and keyboard accelerators (such as Alt and Ctrl).

Italic

Indicates new or technical terms, system calls, URLs, hostnames, email addresses, filenames, file extensions, pathnames, and directories.

Constant width

Indicates commands, options, switches, variables , attributes, keys, functions, types, objects, HTML tags, macros, the contents of files, or the output from commands.

  Constant width bold  

Shows commands or other text that should be typed literally by the user .

Constant width italic

Shows text that should be replaced with user-supplied values.

This icon signifies a tip, suggestion, or general note.

This icon indicates a warning or caution.