Message-ID: <1999Feb404.21.28.6085@koobera.math.uic.edu>
Date: 4 Feb 1999 04:21:28 GMT
Newsgroups: comp.security.unix,comp.dcom.net-analysis
Subject: The Internet has grown past 51 million IP addresses
References: <1998Dec201.08.15.17101@koobera.math.uic.edu>
Organization: IR

Domains found by my latest DNS survey:

   103 *.in-addr.arpa domains responding NOERROR to NS queries
   13108 *.*.in-addr.arpa domains responding NOERROR to NS queries
   911516 *.*.*.in-addr.arpa domains responding NOERROR to NS queries
   51676133 *.*.*.*.in-addr.arpa domains with PTR records

Some IP addresses had multiple PTR records. There were 52540078 PTR
records overall. As pointed out by Mark Lottor and several other people,
this type of survey is unaffected by zone-transfer restrictions.

The number of live computers on the Internet during the survey period
might have been significantly smaller or larger than 51 million, for
several reasons:

   * One computer may have several names and several IP addresses. (One
     corporation has a firewall with literally thousands of addresses.)

   * Dead computers may have names and IP addresses.

   * Computers can be on the Internet without being listed in any PTR
     records, although they are cut off from some Internet services.

   * A huge number of DNS lookups---including more than 400000 of the
     *.*.*.in-addr.arpa lookups, as well as *.{8,39}.in-addr.arpa---
     failed. A failure may be temporary; the PTR record might actually
     exist. (Most common problem: referrals to clueless servers. Second
     most common problem: referrals to unresponsive servers.)

This survey started in December 1998 and finished in January 1999, using
the software in http://pobox.com/~djb/surveydns.html. Most of the
surveying time was spent on address lookups for referrals without glue.
I plan to carry out a second survey using new software that caches the
results of these lookups; I expect that survey to be much faster.

---Dan