recommended users to 5000-7000 users

@Mahesh: nice find. Unfortunately, the results overly emphasize the D series models. Any E series model will outperform it's series D sibling 3-10x, at the same price.

IMHO there are 2 main criteria if you have a high number of users:

- bandwidth

- session buldup rate

For the bandwidth calculation you can use the FTNT calculator (just disregard the model recommodation). Of course, the existing WAN line specs will give you the maximum bw attainable.

Then, if (say) 85% of concurrent users are just surfing, each page view will open a lot of sessions. All current models do have enough memory so the max. number of sessions of a midrange FGT will suffice. If a user calls 2 sites per minute (at peak time), and thus opens ~ 50 sessions per minute, with 85% of 5.000 users (~ 4.250 users) the FGT needs to open ~ 3.500 sessions per second on average (which is tiny) but ~212k session per second at peak load.

Then for the other 15% power users and servers, add another 50% load.

As an example, the FG-2000E is rated with 500k sessions per second, and 5 Gbps traffic with UTM - which is not too far away. So IMHO you need a midrange model 2000E or higher, E series and not D series.