Max Call Simultaneous

Hi all,

I wanted to ask a parry, I ran a crash test with the program sipp to test the limits of the machine.
finding a strange problem, flow around the 220 call the system asterisk starts to reject all calls. Is there any limitation as to just touch the threshold BEGINNING missed calls.
test in monitoring the status of the server, but the same never reaches critical thresholds for CPU and memory, the only service that dramatically scale and asterisk.
There is a limitation on the number of software calls Simultaneous maximum?
The server these features CPU and 2GB of 2400 Mhz Ram
Asterisk is version


Did the Asterisk CLI tell you anything when the trouble started?