Set ulimit To Increase Concurrent Call On Asterisk.

Increase the number of file descriptors (FDs) ie. “Max number of open files” using ulimit command to allow asterisk to handle more than 200 concurrent calls

To increase FDs permanently, go to /etc/security/limits.conf
root             soft   nofile          20000
root             hard   nofile          25000

Reboot your system and check the limits
#ulimit –n    It returns SOFT limit
#ulimit –n –H   It return HARD limit

You also have to use ‘ulimit –n <number of FDs>’ in asterisk startup script

#vi /etc/init.d/asterisk

                -------

                ---------

                                                ulimit –n 20000

                                                /usr/sbin/asterisk

It is always a good idea to check if your asterisk process is really using the ulimit specified by you or not. You can check that by looking into the process itself.  Check the field ‘Max Open Files’.

                #cat /proc/`pidof asterisk`/limits

Note:  `pidof asterisk` returns PID(Process ID) of asterisk