I have a small business network setup I'm working on with a D-Link DFL-80 separating the internal network from the T1 (which is split between two buildings upstream). On the DMZ side of the firewall, I'm running a server with 8 sites pushing an average of about 8-12 kilobits/second incoming data and probably at least five to ten times that outgoing. The Internal side has roughly 14 computers mainly talking amongst themselves (via a 24-port switch with one port as the uplink to the firewall) and occasionally accessing the internet.
Recently the network has been slowing drastically when accessing the internet from the internal network and the websites from a remote site. My first instincts point to maxing out the firewall's processing capabilities with so much traffic, but could it be pushing the limits of the half-T1? If it is the firewall, what would the next step up be? And if it's possibly the T1, is there anything that could be done about it? Lastly, regarding the 1.5Mb speed for a T1, is that half-duplex or full-duplex