If you're only running the MS SQL Server on that box, then using PerfMon, and adding the requisite network counters will give you a view of approximately how much is hitting that server.
If you want to go deeper, and find out exactly how much hits the DB server, then you need to head into the protocol analysis.
This should be available to your Network admin (just ask how much traffic hits the SQL Server port on your box).
By preference, I put firewalls in front of servers. This also gives an advantage of having all the protocol stats at my disposal. Linux with a nicely configured iptables works a treat!