rfc1635.txt

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Network Working Group                                         P. Deutsch
Request for Comments: 1635                                     A. Emtage
FYI: 24                                                           Bunyip
Category: Informational                                        A. Marine
                                                               NASA NAIC
                                                                May 1994


                        How to Use Anonymous FTP

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.

Abstract

   This document provides information for the novice Internet user about
   using the File Transfer Protocol (FTP).  It explains what FTP is,
   what anonymous FTP is, and what an anonymous FTP archive site is.  It
   shows a sample anonymous FTP session.  It also discusses common ways
   files are packaged for efficient storage and transmission.

Acknowledgements

   This document is the result of work done in the Internet Anonymous
   FTP Archives (IAFA) working group of the IETF.  Special thanks are
   due to Mark Baushke (Cisco), John Curran (BBN), Aydin Edguer (CWRU),
   Rafal Maszkowski (Onsala Space Observatory), Marsha Perrott
   (PREPnet), Bob Peterson (Texas Instruments), Nathan Torkington
   (Victoria University of Wellington), and Stephen Tihor (NYU) for
   excellent comments and contributions.

What is FTP?

   FTP refers to the File Transfer Protocol [1], one of the protocols
   within the TCP/IP protocol suite used on the Internet.  The File
   Transfer Protocol makes it possible to transfer files from one
   computer (or host) on the Internet to another.  There are many FTP
   implementations built on the specification of the FTP protocol.  A
   user of an FTP program must log in to both hosts in order to transfer
   a file from one to the other.

   It is common for a user with files on more than one host to use the
   FTP program to transfer files from one host to another.  In this
   case, the user has an account on both hosts involved, so he has
   passwords for both hosts.



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RFC 1635                       How To FTP                       May 1994


   However, Internet users may also take advantage of a wealth of
   information available from archive sites by using a general purpose
   account called "anonymous FTP".

What is an Archive Site?

   An archive site is a host that acts as a repository of information,
   much like a conventional library.  Information stored on these
   Internet hosts is made available for users to transfer to their local
   sites.  Users run software to identify this information and transfer
   it to their own hosts.  Such a transfer is done with a program that
   implements the File Transfer Protocol (FTP).

What is Anonymous FTP?

   Anonymous FTP is a means by which archive sites allow general access
   to their archives of information.  These sites create a special
   account called "anonymous".  User "anonymous" has limited access
   rights to the archive host, as well as some operating restrictions.
   In fact, the only operations allowed are logging in using FTP,
   listing the contents of a limited set of directories, and retrieving
   files.  Some sites limit the contents of a directory listing an
   anonymous user can see as well.  Note that "anonymous" users are not
   usually allowed to transfer files TO the archive site, but can only
   retrieve files from such a site.

   Traditionally, this special anonymous user account accepts any string
   as a password, although it is common to use either the password
   "guest" or one's electronic mail (e-mail) address.  Some archive
   sites now explicitly ask for the user's e-mail address and will not
   allow login with the "guest" password.  Providing an e-mail address
   is a courtesy that allows archive site operators to get some idea of
   who is using their services.

What Information Do You Need to Know?

   To retrieve a specific file, a user needs to know what host it is on,
   and the pathname of the file.  A pathname tells the directory (and
   possibly subdirectories) that house the file, and the name of the
   file.  Often discussions of available files will not specifically
   say, "This file is available for anonymous FTP from X host with Y
   pathname".  However, if a file is publicly announced as available and
   referred to as something like pub/good-stuff on nisc.sri.com, it is a
   good assumption that you can try to transfer it.

   You may also need to know if your machine uses an ASCII, EBCDIC, or
   other character set to know how likely a transfer of binary
   information will work, or whether such a transfer will require other



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   keywords, such as is true for TENEX.

   In the general case, you may assume that an ASCII transfer will
   always do the right thing for plain text files.  However, more and
   more information is being stored in various compressed formats (which
   are discussed later in this document), so knowing the binary
   characteristics of your machine may be important.

A Sample Session

   To start an FTP session on a UNIX or VMS host, you type "ftp" and the
   host name or host IP address of the machine to which you want to
   connect.  For example, if you wish to access the NASA Network
   Applications and Information Center archive site, you would normally
   execute one of the following commands at the UNIX prompt:


           ftp naic.nasa.gov
   or
           ftp 128.102.128.6

   Observe that the first form uses the fully-qualified domain name and
   the second uses the Internet address for the same host.

   The following is an example of connecting to the naic.nasa.gov host
   to retrieve STD 9, RFC 959, "File Transfer Protocol (FTP)" [1].

   Note several things about the session.

    1. Every response the FTP program at the archive site gives
       is preceded by a number.  These numbers are called
       Reply Codes and are defined in the FTP specification,
       RFC 959.  The text that accompanies these reply codes
       can vary in different FTP implementations, and usually does.

       Also note that some FTP client implementations (e.g., MVS
       systems) may not echo the reply codes or text as
       transmitted from the remote host.  They may generate their
       own status lines or just hide the non-fatal replies
       from you.  For the purposes of this document, the more
       popular UNIX interface to the FTP client will be
       presented.

    2. The password you type is never shown on your screen.

    3. It is possible to "browse" in archives, but most often users
       already know the pathname of the file they want.  The pathname
       for RFC 959 on this host is files/rfc/rfc959.txt.  In the



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       example, we first connect to the 'files/rfc' directory (cd
       files/rfc), then get the specific file we know we want.  If you
       do not know the name of the file you want, a file called README
       or something similar (00README.1ST, AAREAD.ME, INDEX, etc.) is
       probably the one to retrieve first.

   atlas.arc.nasa.gov% ftp naic.nasa.gov
   Connected to naic.nasa.gov.
   220 naic.nasa.gov FTP server (Wed May 4 12:15:15 PDT 1994) ready.
   Name (naic.nasa.gov:amarine): anonymous
   331 Guest login ok, send your complete e-mail address as password.
   Password:
   230-----------------------------------------------------------------
   230-Welcome to the NASA Network Applications and Info Center Archive
   230-
   230-     Access to NAIC's online services is also available through:
   230-
   230-        Gopher         - naic.nasa.gov (port 70)
   230-    World-Wide-Web - http://naic.nasa.gov/naic/naic-home.html
   230-
   230-        If you experience any problems please send email to
   230-
   230-                    [e-mail]
   230-
   230-                 or call [phone]
   230-----------------------------------------------------------------
   230-
   230-Please read the file README
   230-  it was last modified on Fri Dec 10 13:06:33 1993 - 165 days ago
   230 Guest login ok, access restrictions apply.
   ftp> cd files/rfc
   250-Please read the file README.rfc
   250-  it was last modified on Fri Jul 30 16:47:29 1993 - 298 days ago
   250 CWD command successful.
   ftp> get rfc959.txt
   200 PORT command successful.
   150 Opening ASCII mode data connection for rfc959.txt (147316 bytes).
   226 Transfer complete.
   local: rfc959.txt remote: rfc959.txt
   151249 bytes received in 0.9 seconds (1.6e+02 Kbytes/s)
   ftp> quit
   221 Goodbye.
   atlas.arc.nasa.gov%








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RFC 1635                       How To FTP                       May 1994


Variations

   The above example is of the FTP program available on UNIX systems.
   Other operating systems also make FTP programs available.  The actual
   commands you type may vary somewhat with other programs.  However, in
   general, you will do the following with every FTP program:

     - Log in to your local host, and invoke the FTP program.

     - Open a connection to the host (using either the host name
       or its IP address)

     - Once connected to the remote host, log in with username
       "anonymous".

     - Provide either the password "guest" or whatever the password the
       site requests.

     - Issue whatever FTP commands you require, such as those to
       change directories or to retrieve a file.

     - When finished, exit the FTP program, which will close your
       connection to the archive host.

Friendly Servers

   These days, many sites are using a form of FTP that allows them to
   display several lines of explanatory text that help direct users
   through their archive.  The listing of alternative services on
   naic.nasa.gov is an example.  If these effusive servers confuse the
   client you are using, try typing a hyphen ( - ) before your password
   when you log in.  That should disable the verbose mode of the server.

Other FTP Commands

   We have demonstrated some of the commands available with FTP
   programs.  Many others are possible.  For example, once you have
   logged in to a remote host:

     - You may ask the FTP program to display a list of available
       commands, typically by invoking the FTP program without
       arguments and typing "help".

     - You may view the contents of the directory to which you are
       connected.  Type "dir" or "ls" to do so.

     - You may rename a file by using the "get" command's
       optional local file name, which follows the remote file



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       name on the command line.  You probably should rename a
       file when the remote file name exceeds your local file
       system's naming constraints, e.g., if the remote file
       name is too long.  An example of using the "get" command
       to rename a file when transferring it might be "get
       really-long-named-file.txt short.txt".

     - You may set BINARY mode to transfer executable programs or files
       of data.  Type "binary" to do so.  Usually
       FTP programs assume files use only 7 bits per byte, the norm for
       standard ASCII-encoded files.  The BINARY command allows you to
       transfer files that use the full 8 bits per byte without error,
       but this may have implications on how the file is transferred
       to your local system.

       If you are not sure what format a file is in, you may need to
       transfer it a second time in the other mode (BINARY or ASCII)
       if your first guess is wrong.  The extension at the end of the
       file name may give you a clue.  File name extensions are
       described below.

       Because some machines store text files differently than others,
       you may have to try your luck if you're not sure what format
       a file is in.  A good guess is to try ASCII mode first, if
       you have grounds to suspect the file is a text file.  Otherwise,
       try BINARY mode.  Try TENEX mode as a last resort.

     - You may transfer multiple files at the same time.  To set this
       mode, type "mget".  You then supply a file name pattern that
       the remote system understands and it tries to transfer each
       file in turn.  If your local FTP user agent cannot transform
       the remote file names into legal local file names, or if there
       are some files that must be transferred in ASCII mode and others
       that must be transferred in BINARY mode, you may not be able to
       take advantage of this facility.

   Full details on the commands and options available are in the FTP
   documentation that comes with your system.  You can also type "help"
   at the FTP command prompt for a list of command options.

   A copy of the UNIX version of the FTP documentation is available from
   the online manual.  If your UNIX site has the manuals installed, type
   the following at the UNIX prompt:

           % man ftp






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RFC 1635                       How To FTP                       May 1994


The Packaging and Naming of Files

   Several widely used conventions allow for efficient storage and
   transmission of information stored at archive sites.

   Information stored on archive sites is often "transformed" in three
   common ways.  "Compressing" (reducing the size of) the stored
   information makes more space available on the archive, and reduces
   the amount of data actually transferred across the network.
   "Bundling" several files into one larger file maintains the internal
   directory structure of the components, and allows users to transfer
   only one larger object rather than several (sometimes hundreds) of
   smaller files.

   In addition, binary data is often converted into an ASCII format for
   transmission, a process referred to in this document as
   "transformation".  Traditionally, Internet RFC 822-based electronic
   mail and USENET protocols did not allow the transmission of "binary"
   (8-bit) data; therefore, files in binary format had to be transformed
   into printable 7-bit ASCII before being transmission.

   On many systems, various file naming conventions are used to help the
   remote user to determine the format of the stored information without
   first having to retrieve the files.  Below we list the more common