Hi,
 
I am analyzing a simple scenario of SIP message exchanges for call setup between two SIP end-point and a sip proxy. The SIP signaling messages for call setup are exchanged between two SIP end-points (using SIPp uac and uas) via the openSER intermediary proxy.
 
Caller                                Callee
SIPp-UAC --> openSER --> SIPp-UAS
 
No delay has been set between 180, 200 responses messages sent by callee (SIPp-UAS).  After using SIPp to create more than 200 cps, openSER starts sending messages out of order (sending 200 before 180). This causes all calls to fail.
 
PS: 1000 cps is tested successfully with SIPp excluding openSER.
 
Is there someone who can give me some advice?
 
Regards,
alirsm