[Live-devel] Live555 scalability issue.

[Ross Finlayson]

>a couple of days ago i conducted some scalability tests with the 
>live555 media server. The computer in test was a quad core that 
>handle the job pretty well and of course a Gigabit port was used. 
>For the last test I used several openRTSP clients. The video source 
>I used was a transport steam file. The normal client downloads an 
>average of 10Mbit/s (1,3Mbytes/s). For the test I created 68 clients 
>all connecting to the same live555 server. The connection sequence 
>was the following, 25 clients, 24 clients, 12 clients and 8. For the 
>first 49 clients the connection was stable and normal, having a 
>total throughput of more than 500Mbit/s. However when connecting the 
>next 12 and 8, the bandwidth was reduced more than 20% for every 
>client i think. Because testing for one  the average speed was less 
>than 8Mbit/s with a total Throughput from the server of around 
>500Mbit/s.
>
>Later when the first 25 clients disconnected and the rest remained, 
>the connection went up  reaching almost 750Mbit for 5 minutes and 
>just for 44 clients, meaning they were compensating I guess for the 
>stream delay. In the end all the remaining clients had a video file 
>almost identical to the original one (missing a few seconds maybe). 
>Why did this happen?

I don't know.  You'll have to explicitly measure exactly where in 
your system the bottleneck(s) are occurring, and exactly what is 
getting overloaded.

Note that there's a lot more in 'your system' than just our software. 
In particular, you have operating systems, CPUs, networks, routers, 
etc.  Any of which could be limiting scalability.

Note in particular that scalability problems with this (and other) 
software is often caused by operating-system-imposed limits on the 
number of open sockets.  Such a limit can usually be increased by 
reconfiguring your OS, so that's one of many things that you might 
try.


>I'm guessing ofcourse this is due to the RTCP protocol.

No, that's highly unlikely.  The overhead of RTCP is negligible.
-- 

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/