Limit users connections?

Hi, Sometimes one user causes a problem and load on the server how I can limit users connections ? Example [root@954 ~]# netstat -plan|grep :80|awk {'print $5'}|cut -d: -f 1|sort|uniq -c|sort -nk 1 1 1 0.0.0.0 - Removed - 2913 156.211.xx.xxx how I can limit users connections ? For example, the upper limit 200 connection for one user