rfc1935.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   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.



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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.



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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.



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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



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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 [e-mail] 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



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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: [e-mail]















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