In addition to a really good firewall Linux has a builtin advanced routing and traffic shaping (lartc).
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I think wondershaper is the canonical tool for simple traffic control. Beyond that (more complicated uses), I haven't found anything easier than just reading the docs and writing my own scripts.
There are some linux-based traffic shaping appliances (rackmounted boxes) around that have (older, less featureful) open source software available. Sorry, I can't recall the product name just now. But yes, there are nicer options than a simple script.