Thank you all guys.
At first I used mod_limitipconn for limiting ip concurrent connections. But I found it got conflict with my mp handler (the PerlAccessHandler one). So I checked its source (it came with a perl version), and found it's easy to be integrated into my handler.And it used Apache::Scoreboard. but the current version of Apache::Scoreboard supports mp2 only.I didn't know the way to find the older version of a module.:) Now got it,thanks.
