What you are describing sounds a lot more like the function of a dedicated QoS system rather than what a typical firewall might be able to provide. The Check Point QoS blade (weights, limits, guarantees, LLQ, DiffServ) and Application Control bandwidth limit capabilities do not really have long-term monitoring capabilities; they are more about immediate management of bandwidth.
I suppose one could parse all firewall Accounting logs on some kind of third-party system and keep running totals of bandwidth utilization per user, utilize the fw samp/sim_dos commands on the firewall to start limiting individuals that have gone over their limit for the month, and then clear those imposed limits at the start of a new month. So yes there is a mechanism for enforcement on the Check Point once someone goes over the monthly limit, but not really a long-term monitoring mechanism to determine when someone has gone "over" and to punish them accordingly. 🙂
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