I searched for a while but couldn't find anything concrete, hopefully someone can help me.

I'm going to be running a Debian server on a gigabit port, and want to give each user his/her fair share of internet access.

The first objective is easy - transfer rates (speed) per user. From what I've looked at, IPTables/Shorewall could do the job easy. Is this easy to setup, or could one of you point me at a config? I was hoping to limit users at 300mbit or 650mbit each.

The second objective gets complicated. Due to the usage of the boxes, most of the traffic will be internal network traffic that does NOT get counted to the quota. However, I still need to limit the external traffic, and if they go over, cut off access (or throttle traffic to a very low speed (10mbit?)). Let's say the user has a 3TB external traffic limit. The IF part is: If the hostname they are exchanging the traffic with DOES NOT MATCH .ovh. or .kimsufi. (company owns multiple TLDs), count to the quota. Once said quota exceeds 3TB, choke them.

Where could I find a system to count that for me? It would also need to reset or be able to be manually reset on a monthly basis.

Thanks ahead of time!