SIPp for ITSP calls

i would like to test my system on how many ITSP calls it can manage, both incoming and outgoing. Could somone help me on how to do that with SIPp and Asterisk please?

A lot depends on your ITSP(s) capacity. You could try simulating them with another Asterisk server B. And then place test calls with SIPp to and from your Asterisk server A.

There are some other similar, interesting testing ideas in this other recent post.