My web host is blocking IPs which make many requests. This includes Googlebot. I found this by checking my webmaster tools account. There it said "network unreachable" for all the URLs which are indexed in Google.
Then I thought of reducing the rate of crawl. I found that Google will not alter the crawl rate. It is only Google who will determine the crawl rate. Users are not allowed to alter the number of requests per time.
Some time ago I had seen the crawl rate settings in Google Webmaster Tools with options like days, week and months. Now it is different. How to set crawl rate for the above different criteria?