Domain survey for counting connected hosts in the Internet

Many people want to know the number of Internet users. It is, however, impossible to count the users directly. Instead, we can count the number of hosts which are connected to the Internet. There have been two methods of counting connected hosts. The first method surveys the DNS (Domain Name System) database, and counts the unique names of computers appearing on it. A host name takes the form of www.waseda.ac.jp. This method gathers DNS records from remote sites, and looks into them. Another method also utilizes DNS records in a different manner. It starts counting hosts with the IP address. There is a DNS record in the database which gives a mapping from an IP address to a host name. The record is called a reverse pointer. The first method is well known and has been used in Japan by JPNIC. Recently, some sites refused to allow their DNS records to be transferred as a whole. They refused the transfer, because illegal intruders sometimes use DNS records to acquire information about their target. Since this security issue is serious, the zone transfer would be refused by many sites. To count the hosts in Japan, we should take the second approach. This paper addresses several issues on host counting and concludes that it is feasible to deploy the second method in Japan although some care should be taken.