MscGen

Mscgen (short for MSC generator) is a software tool for drawing message sequence charts from a simple to manage text-based source file. Rendered charts can be output in PNG, SVG and PostScript, with hyperlink information in ismap format. There is an extension for MediaWiki, Sphinx (documentation generator) and integration with Doxygen that allows embedding of charts into source code comments with generated automatically inserted into the generated documentation page. Mscgen is free software licensed under the GNU General Public License (GPL).

Examples
The following example is from the author:



Here are two examples of input and output for some standard SIP message flows: