The team used the source code from sip-router.org GIT repository from January 2010, which corresponds to Kamailio (former OpenSER) and SER v3.0. The latest stable series v3.1 shares the same internal architecture with v3.0.
As part of the research work, he could also gather some figures about capacity and performances of v3.0 with a quite complex configuration file (involving authentication and NAT traversal as well).
You can read the paper about energy efficiency at:
- one instance of SIP server with 500 000 online users (mixed users - behind and not NAT routers) - consumed energy 210W
- one instance of SIP server with 1 000 000 online users (no NAT involved) - consumed energy 190W
- on a 32-bit machine with 4GB of memory and with 2.5GB reserved for SIP server, the server could support 43 000 simultaneous TLS connections - consumed energy 209W
- 80 000 permanent TCP connections, the SIP server could still handle at least 1000 requests per second and a connection arrival rate of 1000 new connections per second, done for 20 000 new connections. CPU load generated by the SIP server was from 6% to 8%.