Quantify number of calls-testing

So I am a newbie to Asterisk. I have worked with a couple of free PBX system in the past, but when it comes to Asterisk my knowledge is limited. I am setting up a test bed to attempt to quantify the number of calls our PBX system can handle over a SIP trunk.

So I have established my trunk between PBX_A and PBX_B

testI> sip show peers Name/username Host Dyn Forcerport Comedia ACL Port Status Description PBX_A Auto (No) No 5060 OK (1 ms) PBX_B Auto (No) No 5060 OK (1 ms)

I have another box in the same LAN that I would then like to simulate about 1000 calls. In the past I would have used iperf to do this. But from my understanding iperf only measure the traffic it generates. I was leaning towards using sipp to generate traffic between PBX_A and PBX_B then monitor this with iptraf. Would this be an acceptable test to give me the data I need?