Dynamic IP Restrictions IIS and DDOS Attacks.

I need to know the best Deny Criteria values for Dynamic IP Restrictions on IIS to protect from DDOS.
and if I was not going to block those IPs,
I need a way to get notifications number of concurrent requests coming and number of requests coming over a period of time.
(can i get those details by analyzing IIS logs? if it is possible how can I do it? )

I highly appreciate your comments.
thank you!