how to limit the same client's connections per sec.?

hi all guys!

 

I have a problem with the same client ip action often have a lot of access to my web server. but i checked these ip,it's legal IP and legal access.

 

So I want to limit the same client's connections per sec.

 

It means limit client connection's frequency.

 

 

help me do this rules !

 

 

thanks