On 10/13/2015 05:53 PM, M S wrote:
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?
Correct. Kamailio uses separate processes (and shared memory) for multi tasking, while rtpengine is a true multi threaded (single process) application. Each thread can handle one request/packet simultaneously. The default value is to launch one thread per CPU core present, but this can be overridden.
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?
Also correct. The userspace part uses OpenSSL, the kernel part uses the kernel's crypto API. In theory, this should mean that any crypto hardware present is automatically used, but I've never tested this.
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).
If you mean that the threads are multiplexing all open sockets, then yes, of course they do.
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).
It doesn't quite work like that. The only existing queue is provided by the OS and it's only used if the incoming requests/packets can't be processed fast enough, which normally only happens when there isn't enough CPU time available and then you start having serious problems (packet jitter/latency/drops, dropped calls etc). Otherwise, during normal operation, the processing time for a single packet is much less then the pps for any given codec and so a lot more calls can be handled. The last number I've heard from a customer was 12k simultaneous calls without any noticeable performance impact (at which point they started running out of ports and couldn't increase the number any more).
Cheers
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