When I want to draw structural directed graphs and network diagrams my first choice is always dot from the graphviz suite. The syntax is reasonably simple and the documentation has lots of examples to serve as go-bys.
The other day, Grant Rettke, whose blog you should definitely follow, had a post on configuring cask. That's something I've been meaning to investigate so I was happy to see his post. But more interesting to me was the example he gave on configuring cask for graphviz-dot-mode, a mode for editing dot files.
If you like syntax highlighting—and who doesn't—and write dot files, this package seems like a useful addition to your Emacs resources. Once again, Emacs shows that it can adapt to whatever task is at hand. Having syntax highlighting and formatting for
dot files is probably not life changing but it does reduce friction a bit in your work flow. And that's always a win.