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RFC 1415

 
 
 

FTP-FTAM Gateway Specification

Part 3 of 3, p. 38 to 58
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8.2. FTAM-Initiated Gateway Service

   The protocol mapping between FTP and FTAM may be one-to-zero (i.e.,
   not mappable), one-to-one, or one-to-many.

   The general steps taken by the FTP-FTAM gateway to provide the FTAM-
   Initiated service are:

        1. Accept an FTAM Initiator request at the FTAM Responder side
           of the gateway.

        2. Map the request to the (set of) corresponding FTP Client

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           function(s).

        3. Acting as an FTP Client, send the FTP Client function(s) to
           the FTP Server.

        4. Accept information returned to the FTP Client side of the
           gateway.  This information originated at the FTP Server.

        5. Map this returned information to a form understood by the
           FTAM Responder side of the gateway.

        6. Send this returned information from the FTAM Responder side
           of the gateway to the FTAM Initiator.

   For each FTAM protocol function, the FTP protocol functions required
   to map it are identified:

      FTAM                FTP

      -----------------------------------------------------------------

      F-BEGIN-GROUP       none

      F-CANCEL            ABOR

      F-CHANGE-ATTRIBUTE  RNFR, RNTO

      F-CHECK             none

      F-CLOSE             none

      F-CREATE            STOR

      F-DATA              ALLO, STOR or RETR or APPE

      F-DATA-END          none

      F-DELETE            DELE

      F-DESELECT          none

      F-END-GROUP         STAT

      F-ERASE             DELE

      F-INITIALIZE        ACCT, PASS, USER

      F-LOCATE            none

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      F-OPEN              MODE, STRU, TYPE

      F-READ              MODE, NLST, RETR, TYPE

      F-READ-ATTRIBUTE    LIST

      F-RECOVER           REST

      F-RESTART           ABOR, REST

      F-SELECT            LIST

      F-TERMINATE         QUIT

      F-TRANSFER          none

      F-P-ABORT           QUIT

      F-U-ABORT           QUIT

      F-WRITE             APPE or STOR, NOOP

   The remainder of this section presents detailed mapping procedures
   for each of the FTAM protocol functions.  Where appropriate, each
   FTAM service primitive is followed by those parameters that are
   relevant to the mapping.  Gateway support for these mappings is
   required.

8.2.1. F-BEGIN-GROUP REQ

        1. Send F-BEGIN-GROUP RESP PDU to FTAM Initiator signifying
           that processes are available to handle concatenated
           requests.

8.2.2. F-CANCEL REQ

        1. Close FTP data connection.
        2. Send ABOR to FTP Server.
        3. Translate FTP Server reply code to equivalent FTAM
           Responder action and diagnostic parameters and send
           parameters to FTAM Initiator via F-CANCEL RESP PDU.
        4. Translate FTAM Initiator action and diagnostic parameters
           to equivalent FTP reply codes and send reply codes to FTP
           Server.

        Note:
        a. F-U-ABORT REQ is a viable alternative to F-CANCEL REQ.
        b. Note that since ABOR is not implemented by all FTP Servers,

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           the remote file may be corrupted, though accessible.

8.2.3. F-CHANGE-ATTRIBUTE REQ

        1. Get original filename from <Filename> parameter and send it
           with an RNFR to the FTP Server.
        2. Get new filename from <Filename> parameter and send it with
           an RNTO to the FTP Server.
        3. Translate FTP Server reply code to equivalent FTAM
           Responder action and diagnostic parameters and send
           parameters to FTAM Initiator via F-CHANGE-ATTRIBUTE RESP
           PDU.
        4. Translate FTAM Initiator action and diagnostic parameters
           to equivalent FTP reply codes and send reply codes to FTP
           Server.

        Note:
        a. Allow for processing an arbitrary number attributes at one
           time.
        b. Allow for responses of "Attribute currently unavailable for
           change" and "Attribute not currently supported".
        c. At a minimum, support the <Filename>, <Permitted Actions>,
           and <Contents Type> parameters.

8.2.4. F-CHECK REQ

        1. Send an F-CHECK RESP PDU to the FTAM Initiator.

8.2.5. F-CLOSE REQ

        1. Send F-CLOSE RESP PDU , with <Action Result> parameter
           value of "Success", to FTAM Initiator.

        Note:
        a. If an error had occurred during transfer, it would have
           been noted before the F-CLOSE REQ.

8.2.6. F-CREATE REQ

        1. Send STOR and zero data bytes to FTP Server.
        2. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator.
        3. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

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8.2.7. F-DATA PDU

        1. If necessary, send ALLO command to FTP Server.
        2. Depending on whether reading or writing, send STOR, RETR,
           or APPE command to FTP Server.
        3. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator.
        4. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

        Note:
        a. The use of an FTP command may be unnecessary.  Sending the
           data on the data connection may be adequate.

8.2.8. F-DATA-END REQ

        1. Close the data connection.
        2. Save mandatory Diagnostic parameter for later use.
        3. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator.
        4. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.2.9. F-DELETE REQ

        1. Send DELE to FTP server.
        2. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator via F-DELETE RESP PDU.
        3. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.2.10. F-DESELECT REQ

        1. Return F-DESELECT RESP PDU, with <Action Result> parameter
           value of "Success", to FTAM Initiator.

8.2.11. F-END-GROUP REQ

        1. Send STAT command sequence to FTP Server.
        2. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic>
           parameters and send parameters to FTAM Initiator via F-END

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           GROUP RESP.
        3. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.2.12. F-ERASE REQ

        1. Send DELE to FTP Server.
        2. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator via F-ERASE RESP PDU.
        3. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.2.13. F-INITIALIZE REQ

        1. Establish initial area for activity attributes.
        2. Save <Responding Presentation Address>, <Initiator
           Identity>, and <Filestore Password> parameter values
           received from FTAM Initiator.
        3. If the destination address was specified in the
           Distinguished Name (or User Friendly Name) used to attach
           to the gateway, save it as the ultimate destination
           address.
        4. If the ultimate destination address is not yet known, look
           at the "@host" portion of the <Initiator Identity>
           parameter for the ultimate destination parameter.
        5. If the ultimate destination address is still not known,
           check if it is available in the <Responding Presentation
           Address> parameter.
        6. Get userid from <Initiator Identity> and send it with USER
           command to FTP Server.
        7. Get password from <Filestore Password> and send it with
           PASS command to FTP Server.
        8. If necessary, send ACCT command to FTP Server.
        9. Negotiate acceptance of mandatory functional units, service
           classes, service types, presentation contexts, and
           attribute groups.
        10. Accept context management functional unit passed by
            Presentation service provider.
        11. Translate FTP Server reply code to equivalent FTAM
            Responder <Action Result> and <Diagnostic> parameters and
            send parameters to FTAM Initiator via F-INIT RESP PDU.
        12. Translate FTAM Initiator <Action Result> and <Diagnostic>
            parameters to equivalent FTP reply codes and send reply
            codes to FTP Server.

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        Note:
        a. Multiple mechanisms are available for specifying the
           destination address: 1) Distinguished Name, or User
           Friendly Name, used in connecting to the gateway (see
           section 4, Use of Gateway Services); 2) user@host format;
           and 3) Inclusion as <Responding Presentation Address>
           parameter value.

8.2.14. F-LOCATE REQ

        Note:
        a. Not supported since FTAM-1 and FTAM-3 don't support this
           primitive.

8.2.15. F-OPEN REQ

        1. Get <Contents Type> and <Processing Mode> parameter values
           from FTAM Initiator.
        2. Send TYPE command to FTP Server.
        3. Send MODE command to FTP Server.
        4. Send STRU command to FTP Server.
        5. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic>
           parameters and send parameters to FTAM Initiator via F-OPEN
           RESP PDU.
        6. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

        Note:
        a. Establishes definite value for presentation context name
           parameter for this data transfer.
        b. Assumes that the <Requested Access> parameter is permitted.

8.2.16. F-READ REQ

        1. If requested file type and file mode are different than
           current settings, send TYPE and MODE to FTP Server.
        2. If <Contents Type> is FTAM-1 or FTAM-3, then send RETR to
           FTP Server.
        3. If <Contents Type> is "NBS-9", then send NLST to FTP
           Server.
        4. If reply code from FTP Server is 1xx, open FTP data
           connection and loop until End-of-File is read on FTP data
           connection.  Inside loop, read block from FTP data
           connection, format FTAM DATA PDU, and send FTAM PDU to FTAM
           Initiator.  At End-of-File on FTP data connection, send
           F-DATA-END and return.

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        5. If reply code from FTP Server is not 1xx, send F-CANCEL REQ
           to FTAM Initiator.
        6. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator via F-READ RESP PDU.
        7. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

        Note:
        a. To send NLST response, TYPE must be ASCII.

8.2.17. F-READ-ATTRIBUTE REQ

        1. Send LIST to FTP Server.
        2. Translate returned information into the <Filename>,
           <Contents Type>, and <Permitted Actions> parameter values
           and return them to the FTAM Initiator.
        3. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator via F-READ-ATTRIBUTE RESP
           PDU.
        4. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.2.18. F-RECOVER REQ

        1. Send REST command to FTP Server.
        2. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator.
        3. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

        Note:
        a. Regime recovery is only possible if the <Recovery
           Functional Unit> parameter was negotiated previously by an
           F-INITIALIZE.

8.2.19. F-RESTART REQ

        1. To interrupt any bulk data transfer in progress, send ABOR
           to FTP Server.
        2. To negotiate the point at which data transfer is to be
           restarted, get <Checkpoint Identifier> parameter from FTAM
           Initiator and send it with REST to FTP Server.

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        3. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator via F-RESTART RESP PDU.
        4. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.2.20. F-SELECT REQ

        1. Get <Filename> parameter and send with LIST command to FTP
           Server to determine whether  or not the file exists.
        2. If file exists, compare the POSIX file access rights with
           the <Requested Access> parameter sent by the FTAM
           Initiator.  If the access rights match, return <Action
           Result> parameter value of "Success", otherwise return
           <Action Result> parameter value of "Failure".
        3. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator via F-SELECT RESP PDU.
        4. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

        Note:
        a. The specified file is binary/text file if one record is
           received or is a directory file if multiple records are
           received.

8.2.21. F-TERMINATE REQ

        1. Send QUIT to FTP Server.
        2. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator via F-TERMINATE RESP PDU.
        3. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.2.22. F-TRANSFER-END

        1. Get <Action Result> parameter value from last F-DATA-END
           and return it to FTAM Initiator as <Action Result>
           parameter of this F-TRANSFER-END.

8.2.23. F-P-ABORT REQ

        1. Send QUIT to FTP Server.
        2. Return <Action Result> parameter value of "Permanent Error"

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           to FTAM Initiator.
        3. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator.
        4. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.2.24. F-U-ABORT REQ

        1. Send QUIT to FTP Server.
        2. Return <Action Result> parameter value of "Permanent Error"
           to FTAM Initiator.
        3. Translate FTP Server reply code to equivalent FTAM
           Responder <Action Result> and <Diagnostic> parameters and
           send parameters to FTAM Initiator.
        4. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

8.3. F-WRITE REQ

        1. Save bulk transfer specification parameter from PDU.
        2. Send NOOP to FTP Server to receive status information.
        3. If the <Bulk Data Transfer Specification, FADU Operation>
           parameter has a value of "File Extend", then send an APPE
           to the FTP Server, otherwise send a STOR to the FTP Server.
        4. If reply code from FTP Server is 200, then accept FTP data
           connection; otherwise send F-CANCEL REQ to FTAM Initiator.
        5. Translate FTP Server reply code to equivalent FTAM Responder
           <Action Result> and <Diagnostic> parameters and send
           parameters to FTAM Initiator.
        6. Translate FTAM Initiator <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply codes and send reply
           codes to FTP Server.

9.  Mapping between FTP Reply Codes and FTAM Parameters

   The focus of the protocol function and representation mappings,
   presented in the previous sections, is on non-error encumbered
   processing.  Though appropriate responses are designated in many
   cases, it is intended that a more thorough use of responses will be
   incorporated into gateway implementations.

   The purpose of this section is to provide a set of mappings between
   FTAM responses (<Action Result> and <Diagnostic>) and FTP responses
   (reply codes).

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   The <Action Result> parameter of the FTAM File Service primitives
   conveys information which summarizes that available in the
   <Diagnostic> parameter.  The value is never less than the most severe
   diagnostic value.  The valid values of this parameter are "Success",
   "Transient Error", and "Permanent Error".  The FTP response text
   should be supplied in the <Further Details> field of the
   <Diagnostics> sequence in the FTAM response and abort messages.

   An FTAM <Action Result> "Success" may be accompanied by a
   <Diagnostic> with value of "Informative Error Type".  These "Success"
   diagnostic messages are associated with error type 0 in the table
   below (and in [ISO8571-3]).  Error type 1 indicates a transient
   error, while type 2 indicates a permanent error.

   An FTP reply consists of a three digit number followed by some text.
   The number is defined as a 3-digit code, each digit of which has a
   special significance.  The first digit conveys approximately the same
   information as the FTAM <Action Result> parameter; i.e., positive,
   transient negative, or permanent negative.

   The FTP specification document [RFC959] explicitly states that the
   list of reply codes should not be expanded beyond that which is
   presented in [RFC959].  This requirement is adhered to in the
   mappings presented in this document.

9.1.  FTP Reply Codes to FTAM Parameters

   This section presents the set of mappings between FTP reply codes and
   their equivalent FTAM action and diagnostic parameters.  Gateway
   support for these mappings is recommended, but not required.  The
   following abbreviations are used for FTAM action parameter values:

        trans   =    transient error
        perman  =    permanent error

      FTP Reply                                    |FTAM Diagnostic
                                                   |
                                                   |
      Code      Text                               |Result   Type Id
      ---------------------------------------------+------------------
      110       Restart marker reply               |success  0    0
      120       Service ready in nnn minutes       |success  0    0
      125       Data connection open, transfer     |
                starting                           |success  0    0
      150       File status okay; about to open    |
                data connection                    |success  0    0
      200       Command okay                       |success  0    0
      202       Command not implemented;           |

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                superfluous                        |success  0    0
      211       System status, or system help      |
                reply                              |success  0    0
      212       Directory status                   |success  0    0
      213       File status                        |success  0    0
      214       Help message                       |success  0    0
      215       NAME system type                   |success  0    0
      220       Service ready for new user         |success  0    0
      221       Service closing control connection |success  0    0
      225       Data connection; no transfer in    |
                progress                           |success  0    0
      226       Closing data connection            |success  0    0
      227       Entering passive mode (h1,h2,..)   |success  0    0
      230       User logged in, proceed            |success  0    0
      250       Requested file action okay,        |
                completed                          |success  0    0
      257       "PATHNAME" created                 |success  0    0
      331       User name okay, need password      |success  0    0
      332       Need account for logon             |success  0    0
      350       Requested file action pending      |
                further information                |success  0    0
      421       Service not available, closing     |
                control connection                 |trans    1    1
      425       Can't open data connection         |trans    1    3
      426       Connection closed, transfer        |
                aborted                            |trans    1    1014
      450       Requested file action not taken,   |
                file unavailable (e.g., file busy) |trans    1    5041
      451       Requested file action aborted,     |
                local error in processing          |trans    1    5028
      452       Requested action not taken,        |
                insufficient storage space         |trans    1    9
      500       Syntax error, command unrecognized |perman   2    5015
      501       Syntax error in parameters or      |
                arguments                          |perman   2    4004
      502       Command not implemented            |perman   2    5016
      503       Bad sequence of commands           |perman   2    1015
      504       Command not implemented for that   |
                parameter                          |perman   2    4003
      530       Not logged in                      |perman   2    2020
      532       Need account for storing files     |perman   2    2008
      550       Requested action not taken; file   |
                unavailable (e.g., file not found, |
                no access)                         |perman   2    3013
      551       Requested action aborted, page     |
                type                               |perman   2    5002
      552       Requested file action aborted,     |
                exceeded storage allocation        |perman   2    9

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      553       Requested file action not taken,   |
                file name not allowed              |perman   2    3024

9.2.  FTAM Parameters to FTP Reply Codes

   This section presents the set of mappings between FTAM diagnostic
   parameters and their equivalent FTP reply codes.  Gateway support for
   these mappings is recommended, but not required.  As previously
   mentioned, type 0 is an informative error type that may be returned
   with a "Success" action result, type 1 is a transient error type, and
   type 2 is a permanent error type.


      FTAM Diagnostic                                   |FTP Reply Code
                                                        |
      Type      Id   Reason                             |
      --------------------------------------------------+--------
                                                        |
      1,2       0    No reason                          |    421
      0         1    Responder error                    |    211
      1,2       1    Responder error                    |    421
      1,2       2    System shutdown                    |    421
      0         3    FTAM mgmt problem, unspecific      |    211
      1,2       3    FTAM mgmt problem, unspecific      |    425
      0         4    FTAM mgmt, bad account             |    221
      2         4    FTAM mgmt, bad account             |    532
      0         5    FTAM mgmt, security not passed     |    211
      2         5    FTAM mgmt, security not passed     |    530
      0         6    Delay may be encountered           |    211
      0         7    Initiator error, unspecific        |    211
      1,2       7    Initiator error, unspecific        |    421
      0         8    Subsequent error                   |    211
      1,2       8    Subsequent error                   |    421
      0         9    Temporal insufficiency of resources|    211
      1,2       9    Temporal insufficiency of resources|    452
      1,2       10   Access req. violates VFS security  |    550
      1,2       11   Access req. violates local security|    550
      2         1000 Conflicting parameter values       |    504
      2         1001 Unsupported parameter values       |    504
      2         1002 Mandatory parameter not set        |    504
      2         1003 Unsupported parameter              |    504
      2         1004 Duplicated parameter               |    504
      2         1005 Illegal parameter type             |    504
      2         1006 Unsupported parameter types        |    504
      2         1007 FTAM protocol err., unspecific     |    426
      2         1008 FTAM protocol err., procedure err  |    426
      2         1009 FTAM protocol err., funct. unit err|    426
      2         1010 FTAM protocol err., corruption err.|    426

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      2         1011 Lower layer failure                |    426
      1,2       1012 Lower layer addressing error       |    426
      1,2       1013 Timeout                            |    426
      1,2       1014 System shutdown                    |    426
      2         1015 Illegal grouping sequence          |    503
      2         1016 Grouping threshold violation       |    503
      2         1017 Inconsistent PDU request           |    503
      2         2000 Association with user not allowed  |    532
      2         2002 Unsupported service class          |    504
      0         2003 Unsupported functional unit        |    211
      2         2003 Unsupported functional unit        |    502
      0         2004 Attribute group error, unspecific  |    211
      1,2       2004 Attribute group error, unspecific  |    504
      2         2005 Attribute group not supported      |    504
      0         2006 Attribute group not allowed        |    211
      2         2006 Attribute group not allowed        |    504
      0         2007 Bad account                        |    211
      2         2007 Bad account                        |    532
      0         2008 Association management, unspecific |    211
      1,2       2008 Association management, unspecific |    532
      2         2009 Association management, bad address|    532
      1,2       2010 Association management, bad account|    532
      0         2011 Checkpoint window error, too large |    211
      2         2011 Checkpoint window error, too large |    426
      0         2012 Checkpoint window error, too small |    211
      2         2012 Checkpoint window error, too small |    426
      0         2013 Checkpoint window error, unsupp.   |    211
      2         2013 Checkpoint window error, unsupp.   |    504
      0         2014 Communications QoS not supported   |    211
      1,2       2014 Communications QoS not supported   |    504
      2         2015 Initiator identity unacceptable    |    532
      0         2016 Context management refused         |    211
      0         2017 Rollback not available             |    211
      0         2018 Contents type list cut by          |
                     responder                          |    211
      0         2019 Contents type list by              |
                     Presentation Service               |    211
      2         2020 Invalid filestore password         |    530
      2         2021 Incompatible service classes       |    530
      1,2       3000 Filename not found                 |    550
      1,2       3001 Selection attributes not matched   |    550
      2         3002 Initial attributes not possible    |    550
      2         3003 Bad attribute name                 |    550
      1,2       3004 Non-existent file                  |    550
      1,2       3005 File already exists                |    553
      1,2       3006 File cannot be created             |    553
      1,2       3007 File cannot be deleted             |    553
      0         3008 Concurrency control not available  |    211

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      2         3008 Concurrency control not available  |    503
      0         3009 Concurrency control not supported  |    211
      2         3009 Concurrency control not supported  |    502
      0         3010 Concurrency control not possible   |    211
      2         3010 Concurrency control not possible   |    503
      0         3011 More restrictive lock              |    211
      1         3011 More restrictive lock              |    450
      1,2       3012 File busy                          |    450
      1,2       3013 File not available                 |    450
      0         3014 Access control not available       |    211
      1,2       3014 Access control not available       |    503
      0         3015 Access control not supported       |    211
      1,2       3015 Access control not supported       |    502
      0         3016 Access control inconsistent        |    211
      1,2       3016 Access control inconsistent        |    503
      0         3017 Filename truncated                 |    211
      0         3018 Initial attributes altered         |    211
      1,2       3019 Bad account                        |    532
      0         3020 Override selected existing file    |    211
      0         3021 Override deleted and recreated     |    211
      0         3022 Create override deleted and        |
                     recreate file with new attributes  |    211
      1,2       3023 Create override, not possible      |    553
      1,2       3024 Ambiguous file specification       |    553
      2         3025 Invalid create password            |    550
      2         3026 Invalid delete password on override|    550
      2         3027 Bad attribute value                |    550
      2         3028 Requested access violation         |    550
      2         3029 Functional unit not available for  |    550
                     requested access                   |
      0         3030 File created but not selected      |    211
      1         3030 Invalid create password            |    550
      0         4000 Attribute non-existent             |    211
      1,2       4000 Attribute non-existent             |    501
      1,2       4001 Attribute cannot be read           |    504
      1,2       4002 Attribute cannot be changed        |    504
      1,2       4003 Attribute not supported            |    504
      2         4004 Bad attribute name                 |    501
      2         4005 Bad attribute value                |    501
      0         4006 Attribute partially supported      |    211
      0         4007 Additional set attribute value     |
                     not distinct                       |    211
      1,2       5000 Bad FADU, unspecific               |    550
      2         5001 Bad FADU, size error               |    501
      2         5002 Bad FADU, type error               |    551
      2         5003 Bad FADU, poorly specified         |    501
      2         5004 Bad FADU, bad location             |    550
      0         5005 FADU does not exist                |    550

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      1         5005 FADU does not exist                |    550
      0         5006 FADU not available, unspecific     |    550
      1,2       5006 FADU not available, unspecific     |    550
      1,2       5007 FADU not available for reading     |    550
      1,2       5008 FADU not available for writing     |    550
      1,2       5009 FADU not available for location    |    550
      1,2       5010 FADU not available for erasure     |    550
      1,2       5011 FADU cannot be inserted            |    550
      1,2       5012 FADU cannot be replaced            |    550
      0         5013 FADU cannot be located             |    550
      1,2       5013 FADU cannot be located             |    550
      2         5014 Bad data element type              |    550
      1,2       5015 Operation not available            |    500
      1,2       5016 Operation not supported            |    502
      0         5017 Operation inconsistent             |    211
      2         5017 Operation inconsistent             |    503
      0         5018 Concurrency control not available  |    211
      1,2       5018 Concurrency control not available  |    503
      0         5019 Concurrency control not supported  |    211
      2         5019 Concurrency control not supported  |    502
      0         5020 Concurrency control inconsistent   |    211
      2         5020 Concurrency control inconsistent   |    503
      0         5021 Processing mode not available      |    211
      1,2       5021 Processing mode not available      |    503
      0         5022 Processing mode not supported      |    211
      2         5022 Processing mode not supported      |    504
      0         5023 Processing mode inconsistent       |    211
      2         5023 Processing mode inconsistent       |    503
      0         5024 Access context not available       |    211
      2         5024 Access context not available       |    503
      0         5025 Access context not supported       |    211
      2         5025 Access context not supported       |    504
      1,2       5026 Bad write, unspecific              |    550
      1,2       5027 Bad read, unspecific               |    550
      0         5028 Local failure, unspecific          |    211
      1,2       5028 Local failure, unspecific          |    451
      0         5029 Local failure, filespace exhausted |    211
      1,2       5029 Local failure, filespace exhausted |    552
      0         5030 Local failure, data corrupted      |    211
      1,2       5030 Local failure, data corrupted      |    451
      0         5031 Local failure, data corrupted      |    211
      1,2       5031 Local failure, data corrupted      |    451
      2         5032 Future file size exceeded          |    451
      0         5034 Future file size increased         |    211
      0         5035 Functional unit invalid in         |
                     processing mode                    |    211
      2         5035 Functional unit invalid in         |
                     processing mode                    |    503

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      0         5036 Contents type inconsistent         |    211
      2         5036 Contents type inconsistent         |    503
      0         5037 Contents type simplified           |    211
      0         5038 Duplicate FADU name                |    211
      1,2       5039 Damage to select/open regime       |    553
      1,2       5040 FADU locking not available on file |    450
      1,2       5041 FADU locked by another user        |    450

9.3.  Future Mapping Problem

   At some point in the future, the FTAM <Responding Presentation
   Address> parameter may be used for purposes other than the current
   use of passing the final destination address in the FTAM-Initiated
   gateway service [NIST86].  If this happens, the destination address
   will have to be passed in another location, such as in the "@host"
   portion of the <Initiator Identity>.  Currently, the FTP-FTAM gateway
   specification permits either mechanism for storage of the ultimate
   destination address.

9.4.  Error Handling

   The minimal acceptable solution for FTAM-Initiated service errors is
   to map FTP failures to FTAM "Unrecoverable error" and return the FTP
   diagnostic string in the FTAM <Further Details> field.  Similarly for
   FTP-Initiated service errors, the minimal acceptable solution is to
   return reply code 221, "Service closing control connection, Logged
   out if appropriate".  While this minimal solution is acceptable, the
   recommended approach for Gateway developers is to implement the
   mappings presented in Section 9.1, FTP Reply Codes to FTAM
   Parameters, and Section 9.2, FTAM Parameters to FTP Reply Codes.

10.  Implementation and Configuration Guidelines

   The intent of this specification is to specify the required
   characteristics and functions of an FTP-FTAM gateway.  The specific
   approach taken to realize these specifications in an operational
   gateway are left to the discretion of the implementor.  We do take
   the liberty, however, of suggesting several ideas concerning the
   configuration and implementation of such gateways.

10.1.  Robustness

   The gateway should be robust enough to handle situations where a
   subset of the FTP and/or FTAM protocols are implemented on a host.

   The gateway should support multiple concurrent FTP and FTAM
   connections.

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   These are requirements for gateway implementations.

10.2.  Well-Known TCP/IP Port

   It is recommended that the FTP-Initiated gateway process listen on
   TCP/IP port 21, the well-known port for FTP listener processes.  As
   the gateway computer is primarily intended to provide gateway
   services,  use of this port will alleviate the need for gateway users
   to specify the desired port when they connect to the gateway.  The
   standard FTP server listener process can then be moved to another
   port that is known to those users (e.g., System Administrators)
   requiring FTP-to-FTP access to the gateway computer.

10.3.  Gateway Listener Processes

   To simplify the administrative overhead on the gateway computer
   system, it is recommended that the FTP-Initiated service and FTAM-
   Initiated gateway listener processes be merged into a single
   executable module.  This single daemon will act as the one and only
   gateway listener processes.  As connections were established with
   hosts, other processes would be created.

10.4.  Implementation Testing

   To assist in the development and evaluation of FTP-FTAM gateway
   prototypes, NIST has developed a test system to evaluate a gateway's
   conformance to the protocol standards [NIST88].

10.5.  POSIX File Naming and Organization

   The OSI profiles do not define a standard manner for an FTAM
   Responder to return file names.

   To avoid unnecessary complexity, proprietary file systems are not
   addressed in these mappings.  Gateway support for POSIX file naming
   and organization conventions is required; i.e., files are assumed to
   be organized in a hierarchical structure in which all of the non-
   terminal nodes are directories and all of the terminal nodes are any
   other type of file.

11.  Security Considerations

   The gateway system may place the burden of authentication on the
   destination system.  However, the gateway must accommodate the
   passing through of all authentication parameters.  The authentication
   parameters of each protocol are applied at the destination and no
   additional parameters are needed for authentication at the gateway.
   As such, no gateway password file is required to support gateway

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   functions.

   It is anticipated that the requirement for a strong authentication
   mechanism will soon replace the most currently used, userid and
   password mechanism.  The U.S. National Security Agency (NSA) has
   already prototyped and has plans field a Message Secure Protocol
   (MSP) as part of the Defense Message System (DMS) Program which will
   soon become the Department of Defense (DoD) mandatory messaging
   system.  MSP utilizes a public key encryption-like mechanism which
   will be used to authenticate users and allow signed operations.  The
   current philosophy is to use this same mechanism for all
   authentication and access control situations, such as logging onto
   remote hosts or gateways.  Detailed specifications for Pre-MSP, used
   in the unclassified though sensitive arena, are scheduled to be
   published in the first quarter of 1993.  The requirement for gateways
   to process PMSP and MSP strong authentication mechanisms will be part
   of all future DoD procurements.

12.  References

   [ISO8571-1]  Information processing systems - Open Systems
                Interconnection - File Transfer, Access and
                Management, Part 1: General Introduction, International
                Standards Organization for Standards, First Edition,
                October 1988.

   [ISO8571-2]  Information processing systems - Open Systems
                Interconnection - File Transfer, Access and Management,
                Part 2: Virtual Filestore Definition, International
                Standards Organization for Standards, First Edition,
                October 1988.

   [ISO8571-3]  Information processing systems - Open Systems
                Interconnection - File Transfer, Access and Management,
                Part 3: File Service Definition, International Standards
                Organization for Standards, First Edition, October 1988.

   [ISO8571-4]  Information processing systems - Open Systems
                Interconnection - File Transfer, Access and Management,
                Part 4: File Protocol Specification, International
                Standards Organization for Standards, First Edition,
                October 1988.

   [ISO8571-5]  Information processing systems - Open Systems
                Interconnection - File Transfer, Access and Management,
                Part 5: Protocol Implementation Conformance Statement,
                International Standards Organization for Standards,
                First Edition.

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   [KILLE92]  Hardcastle-Kille, S., "Using the OSI Directory to achieve
              User Friendly Naming", OSI-DS 24 (v1.1), October 1992.

   [MITRE87]  Scott, J., "An FTP/FTAM Application Bridge, An FTAM/FTAM
              (MTR-87W00186)", The MITRE Corporation, July 1987.

   [NETWRX90a]  Mindel, J., "Gateway Technical Specification" Open
                Networks, Inc. (formerly NetWorks One), 28 February 1990.

   [NETWRX90b]  Mindel, J., "FTP Gateway User's Guide", Open
                Networks, Inc. (formerly NetWorks One), 28 February 1990.

   [NIST86]  Wallace, M, et. al., "A Gateway Architecture Between FTP
             and FTAM (ICST/SNA86-6)", National Institute of Standards
             and Technology, U.S. Department of Commerce, July 1986.

   [NIST88]  A Test System for Implementations of FTAM/FTP Gateways:
             Final Report Part 1, National Institute of Standards and
             Technology, U.S. Chamber of Commerce, October 1988.

   [NIST91]  CSL Bulletin: File Transfer, Access, and Management,
             National Institute of Standards and Technology, U.S.
             Chamber of Commerce, July 1991.

   [NIST92]  Stable Implementation Agreements for Open Systems
             Interconnection Protocols: Part 9 - FTAM Phase 2, Output
             from the March 1992 Open Systems Environment Implementors'
             Workshop (OIW), March 1992.

   [RFC959]  Postel, J., and J. Reynolds, "File Transfer  Protocol
             (FTP), STD 9, RFC 959, USC/Information Sciences Institute,
             October 1985.

   [RFC1101] Mockapetris, P., "DNS Encoding of Network Names and other
             Types",  RFC 1101, USC/Information Sciences Institute,
             April 1989.

   [RFC1279] Hardcastle-Kille, S., "X.500 and Domain", RFC 1279,
             University College London, November 1991.

   [ROSE90]  Rose, M., "The Open Book: A Practical Perspective on OSI",
             Prentice-Hall Inc., 1990.

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13.  Authors' Addresses

   Joshua L. Mindel
   Open Networks, Inc.
   11490 Commerce Park Dr., Suite 205
   Reston, Virginia 22091  USA

   Phone:  (703) 648-0013
   Email: mindel@netwrx1.nw1.com


   Robert L. Slaski
   Open Networks, Inc.
   11490 Commerce Park Dr., Suite 205
   Reston, Virginia 22091  USA

   Phone:  (703) 648-0013
   Email: slaski@netwrx1.nw1.com