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rfc:rfc1935

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 © 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

Quarterman & 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-capable

Quarterman & 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 servers

Quarterman & 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 is

Quarterman & 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 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.

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 outside

Quarterman & 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 users

Quarterman & 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.com

Quarterman & Carl-Mitchell Informational [Page 11]

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