Network Working Group                                      J. Quarterman
Request For Comments: 1935                               S. Carl-Mitchell
Category: Informational                                               TIC
                                                               April 1996

What 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 the

   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,

   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-capable

   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 servers

   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 is

   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 uses RFC-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 not
   RFC-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.

   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.

   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.

   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 outside

   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 users

   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.com