N-1-3-040.31.4, "Current Sizes of Major Global Networks", by John S. Quarterman, Note to the editor: *indicates italics* The *Matrix* is all the computer networks worldwide that exchange electronic mail or news. How many computers is that? No one knows for sure, but we can make a rough estimate by adding up the numbers of hosts on the biggest global networks. Numbers are available for BITNET, FidoNet, UUCP, the Internet, and USENET, for the end of July 1992. There are thousands of networks in the Matrix; these are not all of them. But these are the biggest networks in the Matrix, and the ones that probably contain most of the hosts. Numbers of Hosts on Some Global Networks in the Matrix network hosts _____________________________ USENET 55,000 _____________________________ BITNET 3,477 FidoNet 16,303 UUCP 14,805 The Internet 992,000 Enterprise IP 600,000 _____________________________ Total 1,612,000 July 1992 Figures compiled by Matrix, Inc., Austin, Texas. +1-512-329-1087 mids@tic.com BITNET, the IBM punchcard image leased line network that supports mail, chat, file sending, and a sophisticated mailing list mechanism, originally connected only IBM mainframes, but now includes many kinds of systems, especially VMS. It has a nodelist called BITEARN NODES, which lists 3,477 BITNET hosts. FidoNet, the dialup personal computer (mostly MS-DOS) network that provides mail and echomail (similar to USENET news), is defined by its nodelist, which lists every node on the network. There are currently 16,303 hosts in the FidoNet nodelist. UUCP, the dialup mail network that was originally all UNIX, but now has many MS-DOS and other hosts, has a node list called the UUCP map. Many UUCP hosts are not registered in the UUCP map, but it is safe to assume 50% to 75% of them are. There are 14,805 hosts registered in the UUCP map. The Internet, the network of more than 5,000 constituent networks that supports mail, news, remote login, file transfer, and numerous other services, has no central registry. However, it is possible to estimate its size by walking the DNS domain tree, and Mark Lottor of SRI has been doing this periodically for years (see RFC 1296, "Internet Growth (1981-1991)"). His latest results, for July 1992, show 992,000 hosts with IP addresses. Many companies have private internal enterprise networks that use IP but are deliberately firewalled from the Internet so that no one can connect in with services such as Telnet or FTP to most parts of them. The SRI results exclude most such IP enterprise networks, although they do include 96,963 hosts under hp.com, or, presumably, all of the HP Internet. The SRI figures do not include much of most other large IP enterprise networks, however. From adding up known sizes for several of the largest such networks, and guessing at the number of others, a conservative estimate would be about 600,000 hosts on such IP enterprise networks. USENET, the news-only virtual network, is carried on top of all of the other networks already mentioned. Brian Reid of Digital has been estimating its size for years, and his latest estimate shows 55,000 hosts. These machines are presumably almost all already counted among the other networks, though, so we have to discard the USENET figure. Adding up these estimates for the various networks, we get more than a million and a half hosts in the Matrix, as shown in the table. For further information, see *Matrix News*, volume 2, numbers 2 and 7, which also include estimates of the numbers of users on the networks.