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Network Working Group                                      J. QuartermanRequest For Comments: 1935                               S. Carl-MitchellCategory: Informational                                               TIC                                                               April 1996What is the Internet, Anyway?Status of This Memo   This memo provides information for the Internet community.  This memo   does not specify an Internet standard of any kind.  Distribution of   this memo is unlimited.Copyright (c) 1994  TIC        From Matrix News, 4(8), August 1994        Permission is hereby granted for redistribution of this article        provided that it is redistributed in its entirety, including        the copyright notice and this notice.        Contact: mids@tic.com, +1-512-451-7602, fax: +1-512-452-0127.http://www.tic.com/mids, gopher://gopher.tic.com/11/matrix/news        A shorter version of this article appeared in MicroTimes.Introduction   We often mention the Internet, and in the press you read about the   Internet as the prototype of the Information Highway; as a research   tool; as open for business; as not ready for prime time; as a place   your children might communicate with (pick one) a. strangers, b.   teachers, c. pornographers, d. other children, e. their parents; as   bigger than Poland; as smaller than Chicago; as a place to surf; as   the biggest hype since Woodstock; as a competitive business tool; as   the newest thing since sliced bread.   A recent New York Times article quoting one of us as to the current   size of the Internet has particularly stirred up quite a ruckus.  The   exact figures attributed to John in the article are not the ones we   recommended for such use, but the main point of contention is whether   the Internet is, as the gist of the article said, smaller than many   other estimates have said.  Clearly lots of people really want to   believe that the Internet is very large.  Succeeding discussion has   shown that some want to believe that so much that they want to count   computers and people that are probably *going to be* connected some   time in the future, even if they are not actually connected now.  We   prefer to talk about who is actually on the Internet and on other   networks now.  We'll get back to the sizes of the various networks   later, but for now let's discuss a more basic issue that is at theQuarterman & Carl-Mitchell   Informational                      [Page 1]

RFC 1935             What is the Internet, Anyway?            April 1996   heart of much confusion and contention about sizes: what is the   Internet, anyway?Starting at the Center   For real confusion, start trying to get agreement on what is part of   the Internet:  NSFNET?  CIX?  Your company's internal network?   Prodigy?  FidoNet?  The mainframe in accounting?  Some people would   include all of the above, and perhaps even consider excluding   anything politically incorrect.  Others have cast doubts on each of   the above.   Let's start some place almost everyone would agree is on the   Internet.  Take RIPE, for example.  The acronym stands for European   IP Networks.  RIPE is a coordinating group for IP networking in   Europe.  (IP is the Internet protocol, which is the basis of the   Internet.  IP has a suite of associated protocols, including the   Transmission Control Protocol, or TCP, and the name IP, or sometimes   TCP/IP, is often used to refer to the whole protocol suite.) RIPE's   computers are physically located in Amsterdam.  The important feature   of RIPE for our purposes is that you can reach RIPE (usually by using   its domain, ripe.net) from just about anywhere anyone would agree is   on the Internet.   Reach it with what?  Well, just about any service anyone would agree   is related to the Internet.  RIPE has a WWW (World Wide Web) server,   a Gopher server, and an anonymous FTP server.  So they provide   documents and other resources by hypertext, menu browsing, and file   retrieval.  Their personnel use client programs such as Mosaic and   Lynx to access other people's servers, too, so RIPE is a both   distributor and a consumer of resources via WWW, Gopher, and FTP.   They support TELNET interfaces to some of their services, and of   course they can TELNET out and log in remotely anywhere they have   personal login accounts or someone else has an anonymous TELNET   service such a library catalog available.  They also have electronic   mail, they run some mailing lists, and some of their people read and   post news articles to USENET newsgroups.   WWW, Gopher, FTP, TELNET, mail, lists, and news:  that's a pretty   characteristic set of major Internet services.  There are many more   obscure Internet services, but it's pretty safe to say that an   organization like RIPE that is reachable with all these services is   on the Internet.   Reachable from where?  Russia first connected to the Internet in   1992.  For a while it was reachable from networks in the Commercial   Internet Exchange (CIX) and from various other networks, but not from   NSFNET, the U.S. National Science Foundation network.  At the time,Quarterman & Carl-Mitchell   Informational                      [Page 2]

RFC 1935             What is the Internet, Anyway?            April 1996   some people considered NSFNET so important that they didn't count   Russia as reachable because it wasn't accessible through NSFNET.   Since there are now several other backbone networks in the U.S. as   fast (T3 or 45Mbps) as NSFNET, and routing through NSFNET isn't very   restricted anymore, few people would make that distinction anymore.   So for the moment let's just say reachable through NSFNET or CIX   networks, and get back to services.Looking at Firewalls   Many companies and other organizations run networks that are   deliberately firewalled so that their users can get to servers like   those at ripe.net, but nobody outside the company network can get to   company hosts.  A user of such a network can thus use WWW, Gopher,   FTP, and TELNET, but cannot supply resources through these protocols   to people outside the company.  Since a network that is owned and   operated by a company in support of its own operations is called an   enterprise network, let's call these networks enterprise IP networks,   since they typically use the Internet Protocol (IP) to support these   services.  Some companies integrate their enterprise IP networks into   the Internet without firewalls, but most do use firewalls, and those   are the ones that are of interest here, since they're the ones with   one-way access to these Internet services.  Another name for an   enterprise IP network, with or without firewall, is an enterprise   Internet.   For purposes of this distinction between suppliers and consumers, it   doesn't matter whether the hosts behind the firewall access servers   beyond the firewall by direct IP and TCP connections from their own   IP addresses, or whether they use proxy application gateways (such as   SOCKS) at the firewall.  In either case, they can use outside   services, but cannot supply them.   So for services such as WWW, Gopher, FTP, and TELNET, we can draw a   useful distinction between supplier or distributor computers such as   those at ripe.net and consumer computers such as those inside   firewalled enterprise IP networks.  It might seem more obvious to say   producer computers and consumer computers, since those would be more   clearly paired terms.  However, the information distributed by a   supplier computer isn't necessarily produced on that computer or   within its parent organization.  In fact, most of the information on   the bigger FTP archive servers is produced elsewhere.  So we choose   to say distributors and consumers.  Stores and shoppers would work   about as well, if you prefer.   Even more useful than discussing computers that actually are   suppliers or consumers right now may be a distinction between   supplier-capable computers (not firewalled) and consumer-capableQuarterman & Carl-Mitchell   Informational                      [Page 3]

RFC 1935             What is the Internet, Anyway?            April 1996   computers (firewalled).  This is because a computer that is not   supplying information right now may be capable of doing so as soon as   someone puts information on it and tells it to supply it.  That is,   setting up a WWW, Gopher, or FTP server isn't very difficult; much   less difficult than getting corporate permission to breach a   firewall.  Similarly, a computer may not be able to retrieve   resources by WWW, Gopher, at the moment, since client programs for   those services usually don't come with the computer or its basic   software, but almost any computer can be made capable of doing so by   adding some software.  In both cases, once you've got the basic IP   network connection, adding capabilities for specific services is   relatively easy.   Let's call the non-firewalled computers the core Internet, and the   core plus the consumer-capable computers the consumer Internet.  Some   people have referred to these two categories as the Backbone Internet   and the Internet Web.  We find the already existing connotations of   "Backbone" and "Web" confusing, so we prefer core Internet and   consumer Internet.   It's true that many companies with firewalls have one or two   computers carefully placed at the firewall so that they can serve   resources.  Company employees may be able to place resources on these   servers, but they can't serve resources directly from their own   computers.  It's rather like having to reserve space on a single   company delivery truck, instead of owning one yourself.  If you're   talking about companies, yes, the company is thus fully on the core   Internet, yet its users aren't as fully on the Internet as users not   behind a firewall.   If you're just interested in computers that can distribute   information (maybe you're selling server software), that's a much   smaller Internet than if you're interested in all the computers that   can retrieve such information for their users (maybe you have   information you want to distribute).  A few years ago it probably   wouldn't have been hard to get agreement that firewalled company   networks were a different kind of thing than the Internet itself.   Nowadays, firewalls have become so popular that it's hard to find an   enterprise IP network that is not firewalled, and the total number of   hosts on such consumer-capable networks is probably almost as large   as the number on the supplier-capable core of the Internet.  So many   people now like to include these consumer-capable networks along with   the supplier-capable core when discussing the Internet.   Some people claim that you can't measure the number of consumer-   capable computers or users through measurements taken on the Internet   itself.  Perhaps not, but you can get an idea of how many actual   consumers there are by simply counting accesses to selected serversQuarterman & Carl-Mitchell   Informational                      [Page 4]

RFC 1935             What is the Internet, Anyway?            April 1996   and comparing the results to other known facts about the accessing   organizations.  And there are other ways to get useful information   about consumers on the Internet, including asking them.Mail, Lists, and News   But what about mail, lists, and news?  We carefully left those out of   the discussion of firewalls, because almost all the firewalled   networks do let these communications services in and out, so there's   little useful distinction between firewalled and non-firewalled   networks on the basis of these services.  That's because there's a   big difference between these communications services and the resource   sharing (TELNET, FTP) and resource discovery (Gopher, WWW) services   that firewalls usually filter.  The communications services are   normally batch, asynchronous, or store-and-forward.  These   characterizations mean more or less the same thing, so pick the one   you like best.  The point is that when you send mail, you compose a   message and queue it for delivery.  The actual delivery is a separate   process; it may take seconds or hours, but it is done after you   finish composing the message, and you normally do not have to wait   for the message to be delivered before doing something else.  It is   not uncommon for a mail system to batch up several messages to go   through a single network link or to the same destination and then   deliver them all at once.  And mail doesn't even necessarily go to   its final destination in one hop; repeated storing at an intermediate   destination followed by forwarding to another computer is common;   thus the term store-and-forward.  Mailing lists are built on top of   the same delivery mechanisms as regular electronic mail.  USENET news   uses somewhat different delivery mechanisms, but ones that are also   typically batch, asynchronous, and store-and-forward.  Because it is   delivered in this manner, a mail message or a news article is much   less likely to be a security problem than a TELNET, FTP, Gopher, or   WWW connection.  This is why firewalls usually pass mail, lists, and   news in both directions, but usually stop incoming connections of   those interactive protocols.   Because WWW, Gopher, TELNET, and FTP are basically interactive, you   need IP or something like it to support them.  Because mail, lists,   and news are asynchronous, you can support them with protocols that   are not interactive, such as UUCP and FidoNet.  In fact, there are   whole networks that do just that, called UUCP and FidoNet, among   others.  These networks carry mail and news, but are not capable of   supporting TELNET, FTP, Gopher, or WWW.  We don't consider them part   of the Internet, since they lack the most distinctive and   characteristic services of the Internet.   Some people argue that networks such as FidoNet and UUCP should also   be counted as being part of the Internet, since electronic mail isQuarterman & Carl-Mitchell   Informational                      [Page 5]

RFC 1935             What is the Internet, Anyway?            April 1996   the most-used service even on the core, supplier-capable Internet.   They further argue that the biggest benefit of the Internet is the   community of discussion it supports, and mail is enough to join that.   Well, if mail is enough to be on the Internet, why is the Internet   drawing such attention from press and new users alike?  Mail has been   around for quite a while (1972 or 1973), but that's not what has made   such an impression on the public.  What has is the interactive   services, and interfaces to them such as Mosaic.  Asynchronous   networks such as FidoNet and UUCP don't support those interactive   services, and are thus not part of the Internet.  Besides, if being   part of a community of discussion was enough, we would have to also   include anyone with a fax machine or a telephone.  Recent events have   demonstrated that all readers of the New York Times would also have   to be included.  With edges so vague, what would be the point in   calling anything the Internet?  We choose to stick with a definition   of the Internet as requiring the interactive services.   Some people argue that anything that usesRFC-822 mail is therefore   using Internet mail and must be part of the Internet.  We find this   about as plausible as arguing that anybody who flies in a Boeing 737   is using American equipment and is thus within the United States.   Besides, there are plenty of systems out there that use mail but notRFC-822.   So what to call systems that can exchange mail, but aren't on the   Internet?  We say they are part of the Matrix, which is all computer   systems worldwide that can exchange electronic mail.  This term is   borrowed (with permission) from Bill Gibson, the science fiction   writer.   Other people refer to the Matrix as global E-mail.  That's accurate,   but is a description, rather than a name.  Some even call it the e-   mail Internet.  We find that term misleading, since if a system can   only exchange mail, we don't consider it part of the Internet.  Not   to mention not everything in the world defines itself in terms of the   Internet, or communicates through the Internet.  FidoNet and WWIVnet,   for example, have gateways between themselves that have nothing to do   with the Internet.  Referring to the Matrix as the Internet is rather   like referring to the United Kingdom as England.  You may call it   convenient shorthand; the Scots may disagree.   What about news?  Well, the set of all systems that exchange news   already has a name: USENET.  USENET is presumably a subset of the   Matrix, since it's hard to imagine a USENET node without mail, even   though USENET itself is news, not mail.  USENET is clearly not the   same thing as the Internet, since many (almost certainly most)   Internet nodes do not carry USENET news, and many USENET nodes are on   other networks, especially UUCP, FidoNet, and BITNET.Quarterman & Carl-Mitchell   Informational                      [Page 6]

RFC 1935             What is the Internet, Anyway?            April 1996   A few years ago it was popular in some corners of the press to   attempt to equate USENET and the Internet.  They're clearly not the   same.  News, like mail, is an asynchronous, batch, store-and-forward   service.  The distinguishing services of the Internet are   interactive, not news.Asynchronous Compared to Dialup   Please note that interactive vs. asynchronous isn't the same thing as   direct vs. dialup connections.  Dialup IP is still IP and can support   all the usual IP services.  It's true that for the more bandwidth-   intensive services such as WWW, you'll be a lot happier with a *fast*   dialup IP connection, but any dialup IP connection can support WWW.   Some people call these on-demand IP connections, or part-time IP   access.  They're typically supported over SLIP, PPP, ISDN, or perhaps   even X.25.   It's also true that it's a lot easier to run a useful interactive   Internet supplier node if you're at least dialed up most of the time   so that consumers can reach your node, but you can run servers that   are accessible over any dialup IP connection whenever it's dialed up.   It's true that some access providers handle low-end dialup IP   connections through a rotary of IP addresses, and that's not   conducive to running servers, since it's difficult for users to know   how to reach them.  But given a dedicated IP address, how long you   stay dialed up is a matter of degree more than of quality.  A IP   connection that's up the great majority of the time is often called a   dedicated connection regardless of whether it's established by   dialing a modem or starting software over a hardwired link.   It's possible to run UUCP over a dedicated IP connection, but it's   still UUCP, and still does not support interactive services.   Some people object to excluding the asynchronous networks from a   definition of the Internet just because they don't support the   interactive services.  The argument they make is that FTP, Gopher,   and WWW can be accessed through mail.  This is true, but it's hardly   the same, and hardly interactive in the same sense as using FTP,   Gopher, or WWW over an IP connection.  It's rather like saying a   mail-order catalog is the same as going to the store and buying an   item on the spot.  Besides, we've yet to see anyone log in remotely   by mail.Is IP Characteristic?   We further choose to define the Internet as being those networks that   use IP to permit users to use both the communication services and at   least TELNET and FTP among the interactive services we have listed.Quarterman & Carl-Mitchell   Informational                      [Page 7]

RFC 1935             What is the Internet, Anyway?            April 1996   This requirement for IP has been questioned by some on the basis that   there are now application gateways for other protocol suites such as   Novell Netware that permit use of such services.  This kind of   application gateway is actually nothing new, and is not yet   widespread.  We choose to think of such networks, at least for the   moment, as yet another layer of the onion, outside the core and   consumer layers of the Internet.   Others have objected to the use of IP as a defining characteristic of   the Internet because they think it's too technical.  Actually, we   find far fewer people confused about whether a software package or   network supports IP than about whether it's part of the Internet or   not.   Some people point out that services like WWW, Gopher, FTP, TELNET,   etc.  could easily be implemented on top of other protocol suites.   This is true, and has been done.  However, people seem to forget to   ask why these services developed on top of IP in the first place.   There seems to be something about IP and the Internet that is   especially conducive to the development of new protocols.  We make no   apologies about naming IP, because we think it is important.   There is also the question of IP to where?  If you have a UNIX shell   login account on a computer run by an Internet access provider, and   that system has IP access to the rest of the Internet, then you are   an Internet user.  However, you will not be able to use the full   graphical capabilities of protocols such as WWW, because the   provider's system cannot display on a bitmapped screen for you.  For   that, you need IP to your own computer with a bitmapped screen.   These are two different degrees of Internet connectivity that are   important to both end users and marketers.  Some people refer to them   as text-only interactive access and graphical interactive access.   Some people have gone so far as to say you have to have graphical   capabilities to have a full service Internet connection.  That may or   may not be so, but in the interests of keeping the major categories   to a minimum, we are simply going to note these degrees and say no   more about them in this article.  However, we agree that the   distinction of graphical access is becoming more important with the   spread of WWW and Mosaic.Conferencing Systems and Commercial Mail Systems   Conferencing systems such as Prodigy and CompuServe that support mail   and often something like news, plus database and services.  But most   of them do not support the characteristic interactive services that   we have listed.  The few that do (Delphi and AOL), we simply count as   part of the Internet.  The others, we count as part of the Matrix,   since they all exchange mail.Quarterman & Carl-Mitchell   Informational                      [Page 8]

RFC 1935             What is the Internet, Anyway?            April 1996   We find that users of conferencing systems have no particular   difficulty in distinguishing between the conferencing system they use   and the Internet.  CompuServe users, for example, refer to "Internet   mail", which is correct, since the only off-system mail CompuServe   supports is to the Internet, but they do not in general refer to   CompuServe as part of the Internet.   Similarly, users of the various commercial electronic mail networks,   such as MCI Mail and Sprint-Mail, seem to have no difficulty in   distinguishing between the mail network they use and the Internet.   Since they all seem to have their own addressing syntax, this is   hardly surprising.  We count these commercial mail networks as part   of the Matrix, but not part of the Internet.  Many of them have IP   links to the Internet, but they don't let their users use them,   instead limiting the services they carry to just mail.Russian Dolls   So let's think of a series of nested Chinese boxes or Russian dolls;   the kind where inside Boris Yeltsin is Mikhail Gorbachov, inside   Gorbachov is Brezhnev, then Kruschev, Stalin, Lenin, and maybe even   Tsar Nicholas II.  Let's not talk about that many concentric layers,   though, rather just three: the Matrix on the outside, the consumer   Internet inside, and the core Internet inside that.                    the core        the consumer    the Matrix                    Internet        Internet    interactive     supplier-       consumer-       by mail    services        capable         capable                    stores and      shoppers        mail                    shoppers                        order    asynchronous    yes             yes             yes services   Some people have argued that these categories are bad because they   are not mutually exclusive.  Well, we observe that in real life   networks have differing degrees of services, and the ones of most   interest share the least common denominator of electronic mail.  Thus   concentric categories are needed to describe the real world.  You   can, however, extract three mutually-exclusive categories by   referring to the core Internet, the interactive consumer-only part of   the Internet, and to asynchronous systems.   Other people have argued that these categories are not sequential.   They look sequential to us, since if you start with the core Internet   and move out, you subtract services, and if you start at the outsideQuarterman & Carl-Mitchell   Informational                      [Page 9]

RFC 1935             What is the Internet, Anyway?            April 1996   of the Matrix and move in, you add services.Outside the Matrix   In addition to computers and networks that fit these classifications,   there are also LANs, mainframes, and BBSes that don't exchange any   services with other networks or computers; not even mail.  These   systems are outside the Matrix.  For example, many companies have an   AppleTalk LAN in marketing, a Novell NetWare LAN in management, and a   mainframe in accounting that aren't connected to talk to anything   else.  In addition, there are a few large networks such as France's   Teletel (commonly known as Minitel) that support very large user   populations but don't communicate with anything else.  These are all   currently outside all our Chinese boxes of the core Internet, the   consumer Internet, and the Matrix.DNS and Mail Addresses   There are other interesting network services that make a difference   to end users.  For example, DNS (Domain Name System) domain names   such as tic.com and domain addresses such tic@tic.com can be set up   for systems outside the Internet.  We used tic.com when we only had a   UUCP connection, and few of our correspondents noticed any difference   when we added an IP connection (except our mail was faster).  This   would be more or less a box enclosing the consumer Internet and   within the Matrix.  But the other three boxes are arguably the most   important.   Some people have claimed that anything that uses DNS addresses is   part of the Internet.  We note that DNS addresses can be used with   the UUCP network, which supports no interactive services, and we   reject such an equation.   It is interesting to note that over the years various attempts have   been made to equate the Internet with something else.  Until the   mid-1980s lots of people tried to say the Internet was the ARPANET.   In the late 1980s many tried to say the Internet was NSFNET.  In the   early 1990s many tried to say the Internet was USENET.  Now many are   trying to say the Internet is anything that can exchange mail.  We   say the Internet is the Internet, not the same as anything else.Summary   So, here we have a simple set of categories for several of the   categories of network access people talk about most these days.  Any   such categories are at least somewhat a matter of opinion, and other   people will propose other categories and other names.  We like these   categories, because they fit our experience of what real usersQuarterman & Carl-Mitchell   Informational                     [Page 10]

RFC 1935             What is the Internet, Anyway?            April 1996   actually perceive.   You'll notice we've avoided use of the words "connected" and   "reachable" because they mean different things to different people at   different times.  For either of them to be meaningful, you have to   say which services you are talking about.  To us, reachable usually   means pingable with ICMP ECHO, which is another way to define the   core Internet.  To others, reachable might mean you can send mail   there, which is another way to define the Matrix.   Once we have terms for networks of interest, we can talk about how   big those networks are.  We think the terms we have defined here   refer to groups of computers that people want to use, and that some   people want to measure.  Many marketers want to know about users.   Well, users of mail are in the Matrix, and users of interactive   services such as WWW and FTP are in the Internet.  Other people are   more interested in suppliers or distributors of information.   Suppliers of information by mail can be anywhere in the Matrix, but   suppliers of information by WWW or FTP are in the core Internet.  It   is easy to define more and finer degrees of distinctions of   capabilities and connectivity, but these three major categories   handle the most important cases.   We invite our readers to tell us what distinctions they find   important about the various networks and their services.Security Considerations   Security issues are not discussed in this memo.Authors' Addresses   John S. Quarterman   Smoot Carl-Mitchell   EMail: tic@tic.comQuarterman & Carl-Mitchell   Informational                     [Page 11]