Generally the number of available file descriptors per process is set to a very conservative value of 1024.
We should probably increase this default when installing IPA for Directory Server.

The change is easy and just requires adding a line for the dirsrv user in limits.conf (pam_limits is already loaded by default in the fedora pam stack).
And change the nssldapd-maxdescriptor attribute in cn=config

I'd propose a value of 8192 by default, which would be enough to server 1500 clients wasting 5 connections each.