[sr-dev] Kamailio vs RTPEngine Performance

Hi, I was asked some interesting questions yesterday by a rather techy client related to Kamailio and RTPEngine performance. Q1: For Kamailio we have say 8 child processes, which means there are 8 threads per listen address to process sip messages, i.e. for example 8 INVITE messages at any instance of time can be processed by Kamailio. If say, one INVITE takes 200ms to be processed and send out to destination, then we can estimate processing power of kamailio to be 40 INVITE requests per second per listen address, right? Q2: If so, then assuming each INVITE requires to engage RTPEngine. How can we ensure that RTPEngine would be capable to handle these 40 INVITE requests? The only relevant parameter I see in RTPEngine daemon script is "NUM_THREADS" (default value 5). What does this represent? Does this analogs to children as in Kamailio? Q3: How does RTPEngine manages SRTP <=> RTP translation (e.g. if one endpoint is WebRTC and other is traditional SIP)? My understanding is that RTPEngine has a kernel module (assuming kernel module is installed) which also manages this conversion besides forwarding the media packets. The Linux kernel already has encoders / decoders for nearly all encryption algorithms which are utilized by RTPEngine for doing the conversion in kernel space, right? if not then how it is done? Q4: Continuing to Q2, If these NUM_THREADS process actual media packets (RTP or SRTP) then are these synchronous or asynchronous? I think these are asynchronous, just want to confirm (otherwise RTPEngine won't process more then e.g. 5 calls at a time). So, assuming asynchronous how many packets can be queue to each thread? This would help estimating RTPEngine throughput using various codecs in calls. (e.g. assuming G.711 codec we have 50pps, if each thread queue size is 1000 then each thread can process 1000/50=20 concurrent calls and whole RTPEngine would process 20x5=100 concurrent calls). Thank you.