Traffic classification

Traffic classification is a much more sophisticated method of blocking traffic than IP blocking, since it can block any file sent through a certain type of protocol, such as FTP. Because FTP transfers are most often sent through TCP port 21, the bandwidth available on that port can be limited, which will throttle transfers. This type of traffic-shaping practice is the most common one used by repressive governments today. It is not resource intensive and it is fairly easy to implement.