[SR-Users] Increase Simultaneous Registration

Hi All I am using Kamailio 4.0.4 (x86_64/linux). I wanted to do simultaneous registrations of large number of endpoints. Many times I see only 2048 endpoints registered and for other endpoints Kamailio did not respond for REGISTER message. I am tcp as transport. Now my questions are 1. What are the different configurations available to increase Kamailio performance 2. If I put Kamailio in a Linux 64 Bit, 2GHz, 8GB RAM machine, how much simultaneous and total registrations can be achieved. I have tuned system file FDs, tcp related configurations like ephemeral port range, and other required configurations. I hope there should be some configurations in Kamailio to achieve higher throughput , can somebody help me out. Thanks Austin