MANY DHCPINFOMR on my log

[blizzards at libero.it]

I have isc dhcp 3.0.4 installed.
I noticed many and many logs like

Oct 26 12:46:01 dns1 dhcpd: DHCPINFORM from xxx.xxx.xxx.xxx via xxx.xxx.xxx.xxx
Oct 26 12:46:01 dns1 dhcpd: DHCPACK to xxx.xxx.xxx.xxx (xx:xx:xx:xx:xx:xx) via xxx.xxx.xxx.xxx

from different clients and i don't know why. Can you tell me why this happen and if this is an error, a bugs and so on??

Thanks.