The Sequence Diagrams seen in the Transactions documentation are generated with Mscgen. Mscgen is a small program to parse Message Sequence Charts that can be represented as text and can then converted to image.
If you need to update the diagrams, please edit the ``.msc`` files present in the diagrams directory (extending/app-layer/diagrams). Once those have been changed, in the ``scripts`` directory (in the main Suricata dir) there's a scrip that will generate images for all files: ``generate-images.sh`` (you'll have to install Mscgen for that to work).
