If you are interested in Windows-way counterparts, we can recommend Traffic Inspector. Simple and reliable, there are cases of operation on networks with several thousand users.
Analogues from the world of unix, you have already recommended. Squid is a very powerful program, with a million pens and krutilki, which you can readjust. This is his strength and weakness. Strength — you can do almost anything, a weakness, a high barrier to entry for inexperienced environment (in nix) admins, it is easy for something to break the reckless actions without understanding the program.