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RFC 1415 - FTP-FTAM Gateway Specification


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Network Working Group                                          J. Mindel
Request for Comments: 1415                                     R. Slaski
                                                     Open Networks, Inc.
                                                            January 1993

                     FTP-FTAM Gateway Specification

Status of the Memo

   This RFC specifies an IAB standards track protocol for the Internet
   community, and requests discussion and suggestions for improvements.
   Please refer to the current edition of the "IAB Official Protocol
   Standards" for the standardization state and status of this protocol.
   Distribution of this memo is unlimited.

Abstract

   This memo describes a dual protocol stack application layer gateway
   that performs protocol translation, in an interactive environment,
   between the FTP and FTAM file transfer protocols.

   Two key assumptions are made:  1) POSIX file naming conventions and
   hierarchical organization, rather than proprietary conventions are in
   use; and 2) X.500 Directory Services are available.

Acknowledgments

   The authors of this RFC would like to express their appreciation to
   the individuals and organizations that participated in the
   implementation of the FTP-FTAM Application Layer Gateway and its
   fielding on the MILNET.  Implementation credits go to Mr. John Scott,
   formerly of the MITRE Corporation, while fielding credits are
   extended to James Graham and R. Greg Lavender of Open Networks, Inc.
   (formerly NetWorks One) and Robert Cooney of the Naval Computer and
   Telecommunications Station (NCTS) Washington.  Dr. Marshall Rose is
   to be commended for recognizing the importance of the FTP-FTAM
   gateway and promulgating it as a part of the ISO Development
   Environment (ISODE).   The following individuals have provided
   valuable editorial comments:  Larry Friedman, Donna Vincent and
   Michael Resnick of Digital Equipment Corporation; Robert Cooney of
   NCTS; and S.E. Hardcastle-Kille of University College London. Funding
   of the FTP-FTAM Gateway Request for Comments effort was provided by
   Open Networks Inc. and the Defense Information Systems Agency (DISA),
   formerly the Defense Communications Agency.  DISA sponsors include
   Len Tabacchi, George Bradshaw, Tom Clarke, and Betsy Turner.

Table of Contents

   1.  Introduction..................................................2
   1.1.   Relationship to Other Work ................................3
   1.2.   Overview of Gateway Operation .............................4
   2.  Gateway Architecture..........................................6
   3.  Network Naming and Addressing.................................8
   4.  Use of the Gateway Services...................................9
   4.1.   FTP-Initiated Gateway Service .............................9
   4.2.   FTAM-Initiated Gateway Service ...........................11
   4.3.   Summary of Usage .........................................12
   5.  Gateway State Variables and Transitions......................13
   5.1.   FTP-Initiated Gateway Service ............................14
   5.2.   FTAM-Initiated Gateway Service ...........................16
   6.  Document Type Support........................................18
   6.1.   Notes on NBS-9 ...........................................18
   7.  Functional Comparison of FTP and FTAM........................19
   7.1.   Loss of Functionality ....................................20
   8. Mapping of Protocol Functions and Representations.............20
   8.1.  FTP-Initiated Gateway Service .............................22
   8.2.  FTAM-Initiated Gateway Service ............................38
   9. Mapping between FTP Reply Codes and FTAM Parameters...........47
   9.1.  FTP Reply Codes to FTAM Parameters ........................48
   9.2.  FTAM Parameters to FTP Reply Codes ........................50
   9.3.  Future Mapping Problem ....................................54
   9.4.  Error Handling ............................................54
   10. Implementation and Configuration Guidelines..................54
   10.1.  Robustness ...............................................54
   10.2.  Well-Known TCP/IP Port ...................................55
   10.3.  Gateway Listener Processes ...............................55
   10.4.  Implementation Testing ...................................55
   10.5.  POSIX File Naming and Organization .......................55
   11. Security Considerations......................................55
   12. References...................................................56
   13. Authors' Addresses...........................................58

1. Introduction

   The TCP/IP and OSI protocol suites will coexist in the Internet
   community for several years to come.  As more and more OSI hosts are
   fielded on the Internet, the requirement for gateways between the two
   protocol suites becomes more pressing.

   This specification describes an application layer gateway providing
   interoperability between the TCP/IP File Transfer Protocol (FTP) and
   the OSI File Transfer, Access, and Management (FTAM) protocol.  The
   proposed application layer gateway is based on a bi-directional set
   of mappings between the FTP and FTAM protocols.  Since the protocols

   have quite different command structures, the mappings between them
   are not one-to-one.  This paper assumes knowledge of the File
   Transfer Protocol (FTP) [RFC959] and the File Transfer, Access, and
   Management Protocol (FTAM) [ISO8571-1,2,3,4,5].

   Two important goals of the mappings are to:

      Provide FTP users with as much emulated FTP capability on an
      FTAM Responder as possible, and

      Provide FTAM users with as much emulated FTAM capability on an
      FTP Server as possible.

   Though it is anticipated that the application layer gateway will be
   implemented on full protocol suites of both TCP/IP and OSI, at least
   one implementation of such a gateway (included in the ISO Development
   Environment) can be configured to operate FTAM over either OSI or
   TCP/IP lower-layer services.

1.1. Relationship to Other Work

   Ideas presented in this specification are based on lessons learned in
   fielding the gateway on the MILNET, operational at NCTS Washington
   D.C. since 1989, and on the efforts of M. A. Wallace et al. of the
   National Institute of Standards and Technology (NIST) [NIST86].  In
   1986, NIST published a design document for an FTP-FTAM gateway.
   Since that time, at least one implementation (for a subset of the FTP
   and FTAM protocols) of the gateway has been developed [MITRE87] and
   is included with the ISODE.  This implementation is based on the NIST
   protocol translator gateway design [NIST86].

   This document's contribution to the advancement of the FTP-FTAM
   gateway concept is to:

      *  Enhance the user interaction capability provided by the ISODE
         implementation of the FTP-FTAM application layer gateway.

      *  Clarify and enhance the mappings (FTP to FTAM, FTAM to FTP)
         documented by NIST.

      *  Provide guidelines for fielding the FTP-FTAM application layer
         gateway on the Internet so that it is useful as an Internet
         resource.

      *  Produce a formal specification for the FTP-FTAM gateway suitable
         for implementors to use in building additional FTP-FTAM
         gateways.

      *  Provide a formal specification for organizations wishing to
         procure FTP-FTAM gateways.

1.2. Overview of Gateway Operation

   The gateway provides a virtual end-to-end application file transfer
   service.  As data is sent via FTP, the gateway immediately maps the
   requested function to FTAM and passes it to the FTAM host.  In a
   similar fashion, but using a different set of mappings, an FTAM
   request is sent to the gateway, immediately mapped to an FTP
   function, and passed along to the FTP host.

   In FTP, the two parties involved in a file transfer are the Client
   and Server.  The Client is responsible for initiating a connection to
   the Server.  Once the connection is established, all service requests
   originate from the Client.  The FTP-FTAM gateway does not support the
   FTP three node model.

   In FTAM, the two parties involved in a file transfer are the
   Initiator and Responder.  The Initiator is responsible for initiating
   a connection to the Responder.  Once the connection is established,
   either the Initiator or Responder may issue service requests to the
   other.

   The FTP-FTAM gateway provides two sets of services:

        1. FTP-Initiated Gateway Services

           Utilized when an FTP Client contacts the FTP-FTAM gateway to
           instigate a file transfer with an FTAM Responder.

        2. FTAM-Initiated Gateway Services

           Utilized when an FTAM Initiator contacts the FTP-FTAM
           gateway to instigate a file transfer with an FTP Server.

   The gateway services' names were selected to identify the roles that
   the FTP-FTAM gateway plays when performing file transfers.  For
   example, when a file transfer is instigated by an FTP Client, it
   contacts the FTP Server portion of the gateway, which maps protocol
   information to the FTAM Initiator portion of the gateway, which in
   turn contacts the remote FTAM Responder.  This example scenario uses
   the FTP-Initiated Gateway Services.

   Figure 1 illustrates the perspective of the application process in
   the FTP-Initiated service.  Figure 2 illustrates that of the FTAM-
   Initiated service.

          TCP Host                                  OSI Host

      +--------------+                        +------------------+

      |  FTP Client  |                        |  FTAM Responder  |

      +--------------+                        +------------------+

             |                                          |

             |                                          |

             |                                          |

             |            FTP-FTAM Gateway              |

             |    +--------------------------------+    |

             +--  |  FTP Server    FTAM Initiator  |  --+

                  +--------------------------------+

             Figure 1  -  FTP-Initiated Gateway Service

          TCP Host                                  OSI Host

      +--------------+                        +------------------+

      |  FTP Server  |                        |  FTAM Initiator  |

      +--------------+                        +------------------+

             |                                          |

             |                                          |

             |                                          |

             |                                          |

             |            FTP-FTAM Gateway              |

             |    +--------------------------------+    |

             +--  |  FTP Client    FTAM Responder  |  --+

                  +--------------------------------+

             Figure 2  -  FTAM-Initiated Gateway Service

2. Gateway Architecture

   The gateway architecture, termed a protocol translator [NIST86], is
   depicted in Figure 3.  It implements TCP/IP and OSI protocol stacks
   with an application level process providing the link between the two.
   The link between FTP and FTAM is defined by two sets of protocol
   mappings, one each for the FTP-Initiated and FTAM-Initiated service
   sets.

      +------------+                               +-------------+

      |  FTP Host  |                               |  FTAM Host  |

      +------------+                               +-------------+

             |                                            |

             |                                            |

             |                                            |

             |                                            |

             |    +---------------------------------+     |

             |    |          FTP  -  FTAM           |     |

             |    |       Gateway Application       |     |

             |    |---------------------------------|     |

             |    |      FTP       |      FTAM      |     |

             |    |----------------+----------------|     |

             |    |    TCP/IP      |    TP4/et al   |     |

             |    +---------------------------------+     |

             |           /|\               /|\            |

             |            |                 |             |

             +------------+                 +-------------+

                  Figure 3  -  Gateway Protocol Stack

   A fundamental aspect of this gateway architecture is that data is
   mapped and transmitted immediately; i.e., no transferred file need
   ever reside on the gateway file system.  In the context of this
   document, the term "filesystem" refers to the file access and
   maintenance mechanisms provided by the operating system.  This lack
   of gateway filesystem interaction helps speed up the end-to-end data
   transfer.  Another speed-enhancing feature of this architecture is
   that both the FTP and FTAM network connections can operate

   simultaneously.  Additional advantages include:

        1. FTP and FTAM hosts require no modification to utilize gateway
           services.

        2. Users require no knowledge of the other protocol.

        3. Gateway access control is not impaired (since users cannot
           directly access the gateway filesystem).

        4. No additional filesystem space is required on the gateway.

        5. Interactive nature of protocols is preserved.

        6. Users become aware of fatal errors immediately.

   Disadvantages of this design include the initial coding effort
   required to develop the gateway and the subsequent re-coding efforts
   required to keep it current.

3. Network Naming and Addressing

   The network naming and addressing schemes used by FTP (Domain Names
   (DN), IP Addresses) and FTAM (Distinguished Names, Presentation
   Addresses) are quite different.  This issue is quite apparent when a
   user of one protocol needs to identify a destination host of the
   other protocol.

   In the TCP/IP naming and addressing scheme, the identity of the FTP
   Server is its DN and its IP address [RFC1101].  To initiate a
   connection to an FTP Server, the FTP Client looks up a DN in either
   the Domain Name System (DNS) or static host table and obtains an IP
   address.

   In the OSI naming and addressing scheme, the identity of the FTAM
   Responder service is its Distinguished Name in the OSI Directory
   (X.500 or static table) and its Presentation address.  The
   Distinguished Name is an authoritative description of the service.  A
   Presentation address consists of a Presentation selector, a session
   selector, a transport selector, and a network address.  To initiate a
   connection to an FTAM Responder, the FTAM Initiator contacts the OSI
   Directory, presents the Distinguished Name of the desired FTAM
   Responder and asks for the Presentation address attribute associated
   with that name.

   An alternative to the direct use of Distinguished Names is to use
   "User Friendly Naming", as defined in [Kille92].  Gateway support for
   "User Friendly Naming" is recommended, but not required.

4. Use of the Gateway Services

4.1. FTP-Initiated Gateway Service

   The FTP Client uses the FTP-Initiated gateway service to utilize the
   resources of an FTAM Responder.

   To initiate a file transfer from an FTP Client, the Client connects
   to the FTP-Initiated gateway service via TCP/IP.  The gateway then
   establishes a connection, via OSI, to the FTAM Responder.  At this
   point, the user can initiate file transfer operations.

   The FTP Client is responsible for providing the gateway with an
   authoritative Distinguished Name, or a User Friendly Name, of the
   desired OSI filestore.  It is the responsibility of the gateway to
   resolve this Distinguished Name, or User Friendly Name, to its
   corresponding Presentation address.

   The logon sequence taken by an FTP Client when initiating a file
   transfer with an FTAM Responder is given below:

             % ftp gateway
             ftp> site Distinguished-Name-of-FTAM Responder
             ftp> user username
             ftp> pass password

   The "ftp gateway" command initiates the connection between the FTP
   Client and the gateway.  Once connected to the gateway, the FTP
   Client should identify the desired FTAM Responder service via the
   Responder's Distinguished Name, or User Friendly Name, which is
   resolved by an algorithm running on the Directory Services provider.
   This information is sent via a "site Distinguished-Name-of-FTAM
   Responder" or "site UFN-of-FTAM Responder" command.

   Upon receipt of a Distinguished Name or a User Friendly Name, it is
   the gateway's responsibility to resolve it to the Presentation
   Address associated with that name.  This resolution is done by
   contacting the OSI Directory (X.500 or local static table) and
   presenting the Distinguished Name or User Friendly Name.  Once the
   Presentation address is obtained, the gateway can attempt a
   connection with the ultimate destination file transfer service
   represented by this Presentation address.

   The userid is passed via the "user username" command, and the
   password is passed via the "pass password".  If the FTAM Responder
   requires a password, a password prompt should appear after issuing
   the "user username" command.  It is anticipated that stronger
   authentication mechanisms will be required for DoD gateways in the

   future.

   Using a specific example, suppose an FTAM Responder has the following
   Distinguished Name:

           CountryName          =         "US"
           Organization         =         "Open Networks"
           OrganizationalUnit   =         "Network Services"
           CommonName           =         "netwrx1"
           CommonName           =         "FTAM service"

   and the FTP-FTAM gateway is available at "washdc1-osigw.navy.mil".

   The FTP user action will appear as:

           % ftp washdc1-osigw.navy.mil
           ftp> site "c=US@o=Open Networks@ou=Network Services@cn=netwrx1
                @cn=FTAM service"
           ftp> user mindel
           ftp> pass ***********

   The "ftp washdc1-osigw.navy.mil" command initiates the connection
   between the FTP Client and the FTP-FTAM gateway at the Washington
   Navy Yard, Washington D.C.  Once connected, the OSI filestore at Open
   Networks is identified via its Distinguished Name, "@c=US@o=Open
   Networks@ou=Network Services@cn=netwrx1@cn=FTAM service".
   Alternatively, a User Friendly Name, such as:

           "netwrx1, Open Networks, us"

   can be specified, enabling the following FTP user action:

           % ftp washdc1-osigw.navy.mil
           ftp> site "netwrx1, Open Networks, us"
           ftp> user mindel
           ftp> pass ***********

   As this example indicates, use of an intermediate gateway is not
   transparent.  To partially alleviate this awkwardness, the gateway
   can be made more transparent through the registration of the FTAM
   host in the DNS using the address of the gateway [RFC1279].

   An example will clarify this point.  Suppose that the "netwrx1, Open
   Networks, us" FTAM host is registered in the TCP/IP DNS with the DN
   of "ftam-service.netwrx1.com" and the IP address of the "washdc1-
   osigw.navy.mil" gateway.  In this example, the following set of user
   actions is required:

           % ftp ftam-service.netwrx1.com
           ftp> user mindel
           ftp> pass ***********

   Since the "ftam-service.netwrx1.com" really points to the gateway
   address, the first command will connect the FTP Client to the
   gateway.  The gateway will then use the name (using [RFC1279]) to
   determine where the actual FTAM host is resident.  Gateway support
   for RFC1279 is recommended, but not required.

4.2. FTAM-Initiated Gateway Service

   The FTAM Initiator uses the FTAM-Initiated gateway service to utilize
   the resources of an FTP Server.

   To initiate a file transfer from an FTAM Initiator, the Initiator
   connects to the FTAM-Initiated gateway service via OSI.  The gateway
   then establishes a connection, via TCP/IP, to the FTP Server.  At
   this point, the user can initiate file transfer operations.

   The FTAM Initiator is responsible for providing the gateway with an
   authoritative DN of the desired TCP/IP filestore.  It is the
   responsibility of the gateway to resolve this DN to its corresponding
   IP address.

   The logon sequence taken by an FTAM Initiator when initiating a file
   transfer with an FTP Server is given below:

           % ftam gateway
           ftam> user username@DNS-string
           ftam> pass password

   The "ftam gateway" command initiates the connection between the FTAM
   Initiator and the gateway.  Once connected, userid and TCP/IP
   filestore are identified in the "username@DNS-string" argument to the
   user command.  If the FTP Server requires a password, a password
   prompt should appear after issuing the user command.

   The gateway should incorporate the BIND Resolver functionality so
   that upon receipt of a Domain Name, the Gateway FTP Client can
   resolve it via the distributed Domain Name System.

   Using a specific example, suppose that a FTP Server has the following
   Domain Name:  "ftp-service.netwrx1.com" and an FTP-FTAM gateway is
   available at:

           CountryName          =         "US"
           Organization         =         "GOV"
           OrganizationalUnit   =         "DOD"
           OrganizationalUnit   =         "DISA"
           Locality             =         "Washington Navy Yard"
           CommonName           =         "wnyosi7"

   The FTAM user action will appear as:

           % ftam @c=US@o=GOV@ou=DOD@ou=DISA@l=Washington Navy Yard
                  @cn=wnyosi7
           ftam> user mindel@ftp-service.netwrx1.com
           ftam> pass ***********

   Alternatively, a User Friendly Name could be used rather than the
   Distinguished Name.

   As mentioned in the previous section, "Use of the FTP-Initiated
   Gateway Service", use of an intermediate gateway is not transparent.
   The gateway can be made more transparent through the registration of
   the FTP host in the X.500 OSI Directory.  By querying the X.500 OSI
   Directory, the gateway can identify where the actual host is
   resident.

   For example, suppose that the FTP Server in the previous example
   ("ftp-service.netwrx1.com") is registered in the X.500 Directory with
   the following Distinguished Name:

           CountryName          =         "US"
           Organization         =         "Open Networks"
           OrganizationalUnit   =         "Network Services"
           CommonName           =         "netwrx1"
           CommonName           =         "FTP service"

   and the Presentation Address of the FTP-FTAM gateway.  This approach,
   described in [RFC1279], would permit the following user interactions:

           % ftam @c=US@o=Open Networks@ou=Network Services
                  @cn=netwrx1@cn=FTP Service"
           ftam> user mindel
           ftam> pass ***********

4.3. Summary of Usage

   As shown in the discussions of the FTP-Initiated and FTAM-Initiated
   Gateway Services, the gateway user does not have access to the
   gateway filesystem; he merely makes use of the gateway logon
   procedure to specify the ultimate destination userid and password.

   Two methods of interaction with the gateway were described.  In the
   former, the user must:

       1. Be aware that a gateway is required to reach the
          destination FTP or FTAM host.

       2. Determine which gateway is most appropriate for their
          respective source-destination pair.

       3. Explicitly connect to the gateway host prior to connecting
          to the destination host.

   Needless to say, the exchange of files between FTP and FTAM hosts
   requires more effort than that required for the exchange of files
   between a pair of hosts utilizing the same file transfer protocol.

   The latter, more transparent method does not necessarily require that
   the user determine which gateway is most appropriate for their
   respective source-destination pair.  In fact, filestore service
   providers are registered using the address of a predetermined
   gateway.  With this approach, the user:

       1. Must be aware that a gateway is required to reach the
          destination FTP or FTAM host.

       2. Need not determine which gateway is most appropriate to
          access their ultimate destination host.

       3. Need not explicitly connect to the gateway prior to
          connecting to the destination FTP or FTAM host.

5. Gateway State Variables and Transitions

   As described, the FTP-FTAM gateway provides two sets of services:
   FTP-Initiated and FTAM-Initiated.  Each service has its own mutually
   exclusive set of state variables and transitions that
   deterministically define the actions of the gateway.  Gateway support
   for these state variables and transitions is required.

   For conciseness in this discussion, FTP-Initiated will be abbreviated
   with "FTP-I", and FTAM-Initiated will be abbreviated with "FTAM-I".

   Concerning error conditions, if a connection is dropped when the
   gateway is in any state other than FTP-I:Initial-State or FTAM-
   I:Initial-State, then the gateway will issue a fatal error message to
   the host with the remaining connection, and then drop that
   connection.  If the remaining host is an FTP Client, then the gateway
   will send an ABOR, QUIT, and 426 reply code (Connection closed,

   transfer aborted).  If it is an FTAM Initiator, then the gateway will
   send an F-P-ABORT with a <Diagnostic> value with identifier 1011
   (Lower layer failure), as well as any known <Further Details>.

   Other error conditions are not addressed in this discussion.

5.1. FTP-Initiated Gateway Service

   The set of state variables for the FTP-Initiated Gateway service
   follow:

  State Variable                State Definition
  ----------------------------------------------------------------

  FTP-I:Initial-State           Initial state of FTP-Initiated Gateway
                                service.

                                Gateway is waiting for an FTP Client to
                                issue a USER command in order to
                                proceed with connection establishment
                                with remote FTAM Responder.  If SITE or
                                ACCT commands are sent while waiting
                                for USER command, save arguments for
                                subsequent use.

  FTP-I:Wait-for-PASS           Gateway has already received USER
                                command from FTP Client, as well as
                                userid and destination host DN.
                                Gateway is waiting for the FTAM
                                Responder logon password.

  FTP-I:Wait-for-PAddress       Gateway has already received PASS
                                command from FTP Client.  Gateway is
                                resolving the provided FTAM Responder's
                                address to a Presentation Address.  The
                                provided address may be a Distinguished
                                Name, User Friendly Name, or Domain
                                Name.  Resolution will typically be
                                done using X.500 directory services.

  FTP-I:Wait-for-Connection     Gateway has initiated a connection to
                                the FTAM Responder and is waiting for
                                notification as to whether or not the
                                logon is successful.

  FTP-I:Wait-for-ClientCmd      Connection exists between FTP Client
                                and FTAM Responder.  Gateway is waiting
                                for next command or response from FTP

                                Client.  Commands and responses are
                                mapped as they are received.

  FTP-I:Wait-for-RespondrCmd    Connection exists between FTP Client
                                and FTAM Responder.  Gateway is waiting
                                for next command or response from FTAM
                                Responder.  Commands and responses are
                                mapped as they are received.

   Each of the possible state transitions is provided in the remainder
   of Section 5.1.  For each state transition, the actions causing the
   transition are listed.

5.1.1. FTP-I:Initial-State   -->   FTP-I:Initial-State

        1. Gateway receives SITE or ACCT command from FTP Client.
           SITE argument includes Distinguish Name of FTAM Responder.

5.1.2. FTP-I:Initial-State   -->   FTP-I:Wait-for-PASS

        1. Gateway receives USER command from FTP Client.  Arguments
           include Distinguished Name of FTAM Responder and userid on
           FTAM responder.

5.1.3. FTP-I:Wait-for-PASS   -->   FTP-I:Wait-for-PAddress

        1. Gateway receives PASS command from FTP Client.

5.1.4. FTP-I:Wait-for-PAddress   -->   FTP-I:Wait-for-Connection

        1. Gateway resolves received Distinguished Name, User Friendly
           Name, or Domain Name of FTAM Responder to OSI Presentation
           address.
        2. Gateway sends F-INITIALIZE to FTAM Responder with
           Presentation Address in <Called Presentation Address>,
           userid in <Initiator Identity>, and password in <Filestore
           Password>.

5.1.5. FTP-I:Wait-for-Connection   -->   FTP-I:Wait-for-NextMapping

        1. Gateway receives <State Result> of "Success" .
        2. Gateway sends 230 reply code (User Logged In) to FTP
           Client.

5.1.6. FTP-I:Wait-for-ClientCmd   -->   FTP-I:Wait-for-RespondrCmd

        1. Gateway receives command or response from FTP Client and
           maps it to FTAM protocol, as defined in section 8.1.

5.1.7. FTP-I:Wait-for-RespondrCmd   -->   FTP-I:Wait-for-ClientCmd

        1. Gateway receives command or response from FTAM Responder
           and maps it to FTP protocol, as defined in section 8.1.

5.1.8. FTP-I:Wait-for-ClientCmd   -->   FTP-I:Wait-for-USER

        1. Gateway receives QUIT command from FTP Client; maps QUIT as
           per Section 8.1.

5.2. FTAM-Initiated Gateway Service

   The set of state variables for the FTAM-Initiated Gateway service
   follow:

  State Variable                State Definition
  ----------------------------------------------------------------

  FTAM-I:Initial-State          Initial state of FTAM-Initiated Gateway
                                Service.

                                Gateway is waiting for an FTAM
                                Initiator to issue an F-INITIALIZE
                                command in order to proceed with
                                connection establishment with remote
                                FTP Server.

  FTAM-I:Wait-for-IPAddress     Gateway has already received F-
                                INITIALIZE from FTAM Initiator.
                                Gateway is resolving the provided FTP
                                Server's address to an IP address.  The
                                provided address may be a Domain Name,
                                Distinguished Name, or User Friendly
                                Name.

  FTAM-I:Wait-for-Connection    Gateway has initiated a connection to
                                the FTP Server and is waiting for
                                notification as to whether or not the
                                logon is successful.

  FTAM-I:Wait-for-InitiatrCmd   Connection exists between FTAM
                                Initiator and FTP Server.  Gateway is
                                waiting for next command or response
                                from FTAM Initiator.  Commands and
                                responses are mapped as they are
                                received.

  FTP-I:Wait-for-ServerCmd      Connection exists between FTAM
                                Initiator and FTP Server.  Gateway is
                                waiting for next command or response
                                from FTP Server.  Commands and
                                responses are mapped as they are
                                received.

   Each of the possible state transitions is provided in the remainder
   of Section 5.2.  For each state transition, the actions causing the
   transition are listed.

5.2.1. FTAM-I:Initial-State   -->   FTAM-I:Wait-for-IPAddress

        1. Gateway receives F-INITIALIZE from FTAM Initiator.  Domain
           Name of FTP Server is either in <Responding Presentation
           Address> or in the "@host" portion of the <Initiator
           Identity> parameter.  The userid is in <Initiator
           Identity>, and password is in <Filestore Password>
           parameter.

5.2.2. FTAM-I:Wait-for-IPAddress   -->   FTAM-I:Wait-for-Connection

        1. Gateway resolves received Domain Name, Distinguished Name,
           or User Friendly Name of FTP Server to IP address.
        2. Gateway sends USER to FTP Server.
        3. Gateway sends PASS to FTP Server.

5.2.3. FTAM-I:Wait-for-Connection  -->   FTAM-I:Wait-for-NextMapping

        1. Gateway receives 230 reply code (User Logged In) from FTP
           Server.
        2. Gateway sends <State Result> of "Success" to FTAM
           Initiator.

5.2.4  FTAM-I:Wait-for-InitiatrCmd   -->   FTAM-I:Wait-for-ServerCmd

        1. Gateway receives command or response from FTAM Initiator
           and maps it to FTP protocol, as defined in section 8.2.

5.2.5. FTAM-I:Wait-for-ServerCmd   -->   FTAM-I:Wait-for-InitiatrCmd

        1. Gateway receives command or response from FTP Server and
           maps it to FTAM protocol, as defined in section 8.2.

5.2.6. FTAM-I:Wait-for-InitiatrCmd  -->  FTAM-I:Wait-for-INITIALIZE

        1. Gateway receives F-CLOSE primitive from FTAM Initiator;
           maps F-CLOSE as per Section 8.2.

6. Document Type Support

   The set of FTAM document types supported by the FTP-FTAM gateway is a
   subset of the document types identified in the Stable Implementation
   Agreements for Open Systems Interconnection Protocols:  Part 9 - FTAM
   Phase 2, produced by the March 1992 Open Systems Environment
   Implementors' Workshop [NIST92].  This subset was chosen for its
   equivalence to those document types supported by FTP.  The set
   includes:

                FTAM-1    "ISO FTAM Unstructured text file

                FTAM-3    "ISO FTAM Unstructured binary file

                NBS-9     "NBS-9 FTAM File directory file"

      FTAM document types map to FTP document types as follows:

                FTAM      <->       FTP
                ----------------------------------

                FTAM-1    <->       ASCII

                FTAM-3    <->       8 bit binary

                NBS-9     <->       Directory

   Gateway support for FTAM-1 and FTAM-2 is required, whereas support
   for NBS-9 is recommended.

6.1. Notes on NBS-9

   NBS-9 is optional in GOSIP versions 1 and 2 [NIST91].  NBS-9 will be
   superseded by its replacement when ISO/IEC ISP 10607-2 and ISO/IEC
   ISP 10607-2/Amendment 1 are published [NIST92].

   For conformance to NBS-9, an FTAM Responder is only required to
   return the <Filename> file attribute, subject to local security and
   access control.  All other requested attributes need not be returned.

   Systems supporting the NBS-9 document type shall make available an
   NBS-9 document called 'DIRLIS'.  This document can be used to obtain
   a listing of files and their associated attributes from a remote
   Filestore.

7. Functional Comparison of FTP and FTAM

   A comprehensive comparison of the services offered by FTP and FTAM is
   beyond the scope of this specification.  What follows is an analysis
   of several key points.  Refer to [NIST 86a] and [ROSE90] for a more
   complete discourse on this topic.

   FTAM is not a superset of FTP; each protocol has functions that only
   it performs.  The set of FTAM functions is, however, larger than the
   set of FTP functions.

   FTP combines file management and file transfer into one protocol
   engine, whereas FTAM separates management and transfer as they relate
   to files.

   The file transfer services of both FTP and FTAM expect a reliable
   underlying end-to-end service.  At a minimum, this service includes
   the capability to transfer entire files between remote hosts and to
   display remote filenames.

   In addition to this basic file transfer service, FTAM supports the
   capability to:  access a few records from a file server, create a
   network file system (similar to Sun's Network File System), handle
   printing and spooling, and access remote database records.  FTP does
   not support these additional capabilities.

   FTP uses TELNET services to set up a connection between the FTP
   Client and FTP Server.  A three-digit reply code followed by
   explanatory text indicates the status of the preceding request and
   provides diagnostic information explaining each transaction.

   FTAM relies on the Association Control Service Element (ACSE) to
   start and stop the network for network file interaction.  Generally,
   the ASCE establishes the application association and related
   application context needed to support the FTAM protocol.

   The FTAM protocol is modularized so as to keep the allowable number
   of actions in any particular state relatively small.  There are many
   more possible sequences of FTP operations than possible sequences of
   FTAM operations [NIST86].

   Because FTAM is more robust than FTP, FTAM allows greater flexibility
   for conveying information about files.  FTAM deals only with aspects
   of application processes, and leaves data representation and data
   management facilities to other OSI service elements.

   In contrast to the Client/Server model present in the FTP scheme,
   FTAM is based on the Initiator/Responder model.  The key distinction

   is that once the FTAM Initiator has established a connection with a
   remote host, either the Initiator or Responder can request services
   of the other.  In the FTP realm, the Client both initiates a
   connection and requests all services.

   The FTP Client knows the real properties of the remote host
   filesystem.  FTAM, in contrast, embraces a conceptual model of a
   filesystem, labeled a virtual filestore model.  The virtual filestore
   is a collection of files, each of which has a name that uniquely
   identifies it.  Each file has a set of attributes, such as ownership
   information and contents, which is the data associated with the file.
   One file attribute is the <Contents Type> of the file, typically of
   value "FTAM-1", "FTAM-3", or "NBS-9".  The FTAM Initiator only knows
   the properties of the corresponding Responder and virtual filestore,
   not the real properties of the filesystem on the remote host.

7.1. Loss of Functionality

   As happens whenever two dissimilar protocols, or languages for that
   matter, are translated, some loss of functionality is inevitable.
   With reference to the FTP-FTAM gateway, several of the most blatant
   losses of functionality are:

        1. Diagnostics passed between protocols may not be precisely
           translated.

        2. The FTAM partial file (record) transfer may not be
           supported.

        3. Some FTAM attributes are not supported by FTP.

   The primary goal of the gateway protocol mappings are to minimize
   this loss of functionality. As this gateway specification and
   subsequent implementations evolve, means to partially overcome loss
   of functionality may become more obvious.  For example, the gateway
   may be able to emulate file record transfers between FTAM Initiators
   and FTP Servers.

8. Mapping of Protocol Functions and Representations

   The mappings presented are based upon the FTAM protocol
   implementation as defined in Stable Implementation Agreements for
   Open Systems Interconnection Protocols:  Part 9 - FTAM Phase 2,
   produced by the March 1992 Open Systems Environment Implementors'
   Workshop [NIST92], and in [ISO8571-1], [ISO8571-2],[ISO8571-
   3],[ISO8571-4], and [ISO8571-5].  The FTP protocol as defined in
   Request for Comments [RFC959].   The mappings are strongly influenced
   by the work of M. A. Wallace et. al. at NIST [NIST86] and John Scott

   at MITRE [MITRE87].

   A key goal of the mappings presented in this document is to minimize
   the loss of functionality between the two protocols.  The specific
   approach taken to implement the mappings is left to the discretion of
   the gateway implementor.  The focus of the protocol function and
   representation mappings is on non-error encumbered processing.  The
   mapping of diagnostic and error messages is treated separately in
   section 9.

   At a minimum, the FTAM implementation in the FTP-FTAM gateway support
   for Implementation Profiles T1 (Simple File Transfer) and M1
   (Management), as defined in [NIST92], is required.  These
   Implementation Profiles correspond to the A/111 and A/13 Profiles of
   Standards Promotion and Application Group in Europe, respectively
   [NIST92].

   At a minimum, the gateway support for the following is required:

      ASCII and 8 bit binary file types.  It should also support FTP
      File Stream Mode.

      The following FTAM document types: FTAM-1 (unstructured text
      file), FTAM-3 (unstructured binary file), and NBS-9 (set of
      directory entries).

   POSIX file naming and organization conventions are assumed in these
   mappings; i.e., files in the systems 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.

   The following terminology is used in the mapping specifications:

      argument .......FTP Service Command argument, as used in [RFC959].

      parameter ......FTAM Service Primitive parameters and attributes,
                      as enumerated in Tables 6, 50, and 51 of [ISO8571-
                      3].

   The following notation is used in the mapping specifications:

      Arguments and parameters are enclosed in angle brackets; e.g.,
      <Action Result>

      Values of arguments and parameters are enclosed in quotation
      marks; e.g., "Success"

      FTP Service Commands and FTAM Primitives are in uppercase; e.g., F-
      INITIALIZE

8.1.  FTP-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 FTP-
   Initiated service are:

        1. Accept an FTP Client request at the FTP Server side of the
           gateway service.

        2. Map the request to the (set of) corresponding FTAM
           Initiator function(s).

        3. Acting as an FTAM Initiator, send the FTAM Initiator
           function(s) to the FTAM Responder.

        4. Accept information returned to the FTAM Initiator side of
           the gateway.  This information originated at the FTAM
           Responder.

        5. Map this returned information to the protocol form
           understood by the FTP Server side of the gateway.

        6. Send this returned information from the FTP Server side of
           the gateway to the FTP Client.

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

   FTP       FTAM

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

   ABOR      F-BEGIN-GROUP, F-CANCEL, F-CLOSE, F-DESELECT, F-END-GROUP

   ACCT      F-INITIALIZE,

   ALLO      none

   APPE      F-BEGIN-GROUP, F-CLOSE, F-CREATE, F-DATA, F-DATA-END, F-
             DESELECT, F-END-GROUP, F-OPEN, F-READ-ATTRIBUTES, F-SELECT,
             F-TRANSFER-END, F-WRITE

   CDUP      F-BEGIN-GROUP, F-DESELECT, F-END-GROUP, F-SELECT

   CWD       F-BEGIN-GROUP, F-END-GROUP, F-DESELECT, F-SELECT

   DELE      F-BEGIN-GROUP, F-DELETE, F-END-GROUP, F-SELECT

   HELP      none

   LIST      F-BEGIN-GROUP, F-CLOSE, F-DATA, F-DATA-END, F-DESELECT, F-
             END-GROUP, F-OPEN, F-READ, F-READ-ATTRIBUTES, F-SELECT, F-
             TRANSFER-END

   MKD       none

   MODE      none

   NLST      F-BEGIN-GROUP, F-CLOSE, F-DATA, F-DATA-END, F-DESELECT, F-
             END-GROUP, F-OPEN, F-READ, F-SELECT, F-TRANSFER-END

   NOOP      none

   PASS      F-INITIALIZE

   PASV      none

   PORT      none

   PWD       F-BEGIN-GROUP, F-DESELECT, F-END-GROUP, F-READ-ATTRIBUTES,
             F-SELECT

   QUIT      F-P-ABORT or F-U-ABORT, F-TERMINATE

   REIN      F-BEGIN-GROUP, F-CANCEL, F-CLOSE, F-DESELECT, F-END-GROUP

   REST      F-CHECK, F-RESTART

   RETR      F-BEGIN-GROUP, F-CLOSE, F-DATA, F-DATA-END, F-DESELECT, F-
             END-GROUP, F-OPEN, F-READ, F-SELECT, F-TRANSFER-END

   RMD       none

   RNFR      F-BEGIN-GROUP, F-DESELECT, F-END-GROUP, F-SELECT

   RNTO      F-BEGIN-GROUP, F-CHANGE-ATTRIBUTES, F-DESELECT, F-END-
             GROUP, F-SELECT

   SITE      F-INITIALIZE

   SMNT      none

   STAT      none

   STOR      F-BEGIN-GROUP,F-CLOSE, F-CREATE, F-DATA, F-DATA-END, F-
             DESELECT, F-END-GROUP, F-OPEN, F-READ-ATTRIBUTES, F-SELECT,
             F-TRANSFER-END, F-WRITE

   STOU      F-BEGIN-GROUP, F-CLOSE, F-CREATE, F-DATA, F-DATA-END, F-
             DESELECT, F-END-GROUP, F-OPEN, F-READ-ATTRIBUTES, F-SELECT,
             F-TRANSFER-END, F-WRITE

   STRU      none

   TYPE      none

   USER      F-INITIALIZE

   The remainder of this section presents detailed mapping procedures
   for each of the FTP protocol functions.  Gateway support for these
   mappings is required.

8.1.1. ABOR

        1. Send F-CANCEL to FTAM Responder.
        2. Send the following grouped request to the FTAM Responder.
           F-BEGIN-GROUP
           F-CLOSE
           F-DESELECT
           F-END-GROUP
        3. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           codes to FTP Client.
        4. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

8.1.2. ACCT

        1. Set <Account> parameter value for issuing F-INITIALIZE to
           FTAM Responder.
        2. If <Called Presentation Address>, <Initiator Identity>, and
           <Filestore Password> parameters are available, attempt
           connection with FTAM Responder;
           Otherwise wait for additional ACCT commands.
        3. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           codes to FTP Client.
        4. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to

           FTAM Responder.

        Note:
        a. The ACCT command will be effective with the next PASS
           command.

8.1.3. ALLO

        1. Return a 200 reply code to FTP Client.

8.1.4. APPE

        1. Save current pathname by appending saved CWD string with
           <pathname> argument.  If no saved CWD string, proceed to
           step 12.
        2. Send the following grouped request to FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-READ-ATTRIBUTES
                Save <Contents Type> parameter value
            F-DESELECT
            F-END-GROUP
        3. If the <Contents Type> parameter value returned with the
           F-READ-ATTRIBUTES has a value of "NBS-9", proceed to step
           12.
        4. Send the following grouped request to the FTAM responder.
            F-BEGIN-GROUP
            F-CREATE
                Set the <Override> parameter in the F-CREATE to
                "Select Old File".
            F-OPEN
            F-END-GROUP
        5. If the file existed, set the <Contents Type> parameter in
           the F-CREATE to match that returned by the
           F-READ-ATTRIBUTES.
        6. If the file did not exist and no previous FTP TYPE "Image"
           command was issued, then set the <Contents Type> parameter
           to "FTAM-1";
           Otherwise, set the <Contents Type> parameter to "FTAM-3".
        7. Send F-WRITE, with <Bulk Data Transfer Specification, FADU
           Operation> parameter set to "File Extend", to FTAM
           Responder.
        8. Loop reading data from FTP data connection, sending the
           data in F-DATA PDUs until end-of-file on the FTP
           connection.
        9. Send F-DATA-END to FTAM Responder.
        10. Send F-TRANSFER-END to FTAM Responder.
        11. Send the following grouped request to the FTAM Responder.

            F-BEGIN-GROUP
            F-CLOSE
            F-DESELECT
            F-END-GROUP
        12. Translate FTAM Responder <Action Result> and <Diagnostic>
            parameters to equivalent FTP reply code(s) and send reply
            code(s) to FTP Client.
        13. Translate FTP Client reply codes to equivalent FTAM
            <Action Result> and <Diagnostic> parameters and send
            parameters to FTAM Responder.

        Note:
        a. <pathname> argument is assumed to be a filename, relative
           to the currently saved CWD.
        b. CWD of the FTAM system must be defined prior to issuance of
           APPE.

8.1.5. CDUP

        1. Determine parent directory from saved CWD string.  If no
           saved CWD string, proceed to step 4.
        2. Set <Contents Type> parameter to "NBS-9".
        3. Send the following grouped request to FTAM Responder.
           F-BEGIN-GROUP
           F-SELECT
           F-DESELECT
           F-END-GROUP
        4. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        5. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. A POSIX file organization is assumed; i.e., files in the
           systems are 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.
        b. If the parent directory does not exist, the current working
           directory remains unchanged.
        c. CWD of the FTAM system must be defined prior to issuance of
           CDUP.

8.1.6. CWD

        1. Save <pathname> argument as CWD string.
        2. Set <Contents Type> parameter to "NBS-9".

        3. Send the following grouped request to FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-DESELECT
            F-END-GROUP
        4. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        5. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. The <pathname> argument is assumed to be an absolute
           directory specification.
        b. If the specified directory does not exist, the current
           working directory remains unchanged.
        c. Saved CWD string is used in other FTP-to-FTAM mappings,
           such as APPE.

8.1.7. DELE

        1. Save current pathname by appending saved CWD string with
           <pathname> argument.  If no saved CWD string, proceed to
           step 3.
        2. Send the following grouped request to FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-DELETE
            F-END-GROUP
        3. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        4. Translate FTP Client reply codes to equivalent FTAM
           parameters and send parameters to FTAM Responder.

        Note:
        a. <pathname> argument is assumed to be a filename, relative
           to the currently saved CWD.
        b. CWD of the FTAM system must be defined prior to issuance of
           DELE.

8.1.8. HELP

        1. If no <string> argument is provided, send helpful
           information about the implementation of the gateway to the
           FTP Client.  If an argument is provided, send more specific
           information.

        2. Return the FTP reply code 214 to the FTP Client.

8.1.9. LIST

        1. If <pathname> argument is provided, proceed to step 3.
        2. Save current pathname by appending saved CWD string with
           <pathname> argument; If no saved CWD string, proceed to
           step 11.
        3. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-READ-ATTRIBUTES
                Save <Filename>, <Contents Type>, <Data/Time of Last
           Modification>, and <Filesize> parameters
            F-DESELECT
            F-END-GROUP
        4. If the <Contents Type> parameter of the F-READ-ATTRIBUTES
           is not "NBS-9", then return the <Filename>, <Contents
           Type>, <Date/Time of Last Modification>, and <Filesize>
           parameter values, obtained with the previous
           F-READ-ATTRIBUTES, to the FTP data connection;
           and proceed to step 8.
        5. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-OPEN
            F-END-GROUP
        6. Send F-READ to FTAM Responder.
        7. Loop reading F-DATA until F-DATA-END.  As data is received,
           write the <Filename>, <Permitted Actions>, <Contents Type>,
           and <Date/Time of Last Modification> parameter values from
           the PDU to the FTP data connection.
        8. Send F-TRANSFER-END to FTAM Responder.
        9. Send the following grouped request to the FTAM responder.
            F-BEGIN-GROUP
            F-CLOSE
            F-DESELECT
            F-END-GROUP
        10. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        11. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. Assume the <pathname> argument is relative to the saved
           CWD, whether filename or directory specification.

        b. CWD of the FTAM system must be defined prior to issuance of
           LIST.
        c. Transfers over data connection should be in ASCII.
        e. If list of files with full directory/file specification is
           received from FTAM Responder, then gateway should parse
           list to strip off directory portion.

8.1.10. MKD

        1. Return a 502 reply code (Command not implemented) to the
           FTP Client.

        Note:
        a. As indicated in the NIST Stable Implementation Agreements
           for FTAM [NIST92], creation or deletion of NBS-9 files is
           outside the scope of the agreements.

8.1.11. MODE

        1. If <argument> is "Stream", return 200 reply code to FTP
           Client; Otherwise return a 504 reply code (Command not
           implemented for that parameter).

8.1.12. NLST

        1. If <pathname> argument is provided, use <pathname> argument
           as <Filename> parameter value in F-SELECT issued in step 3.
        2. If no argument is provided, use saved CWD value as
           <Filename> parameter value in F-SELECT issued in step 3; If
           no CWD string is saved and no argument is provided, proceed
           to step 9.
        3. Set <Contents Type> parameter to "NBS-9".
        4. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-OPEN
            F-END-GROUP
        5. Send F-READ to FTAM Responder.
        6. Loop reading F-DATA until F-DATA-END.  As data is received,
           write the filenames and other useful information from the
           PDU to the FTP data connection.
        7. Send F-TRANSFER-END to FTAM Responder.
        8. Send the following grouped request to the FTAM responder.
            F-BEGIN-GROUP
            F-CLOSE
            F-DESELECT
            F-END-GROUP
        9. Translate FTAM Responder <Action Result> and <Diagnostic>

           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        10. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. As per RFC 959 (FTP), the NLST <pathname> argument is a
           directory.
        b. Assume the argument is relative to the saved CWD, whether
           filename or directory specification.
        c. CWD of the FTAM system must be defined prior to issuance of
           NLST.
        d. Transfers over data connection should be in ASCII.
        e. Gateway should parse full directory/file specifications
           received from FTAM Responder to strip off directory
           portion.  This is required to support the "FTP multiple
           get" function that pipes NLST output to the STOR command.

8.1.13. NOOP

        1. Return a 200 reply code to FTP Client.

8.1.14. PASS

        1. Set <Filestore Password> parameter for F-INITIALIZE.
        2. If <Called Presentation Address>, <User Identity>, and
           <Filestore Password> are available, issue F- INITIALIZE to
           FTAM Responder.
        3. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        4. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

8.1.15. PASV

        1. Wait for data transfer on default data port or data port
           specified by PORT command.
        2. Return a 200 reply code to FTP Client.

8.1.16. PORT

        1. Return a 200 reply code to FTP Client.

8.1.17. PWD

        1. If there is a saved CWD string, return it to the FTP client
           and proceed to step 4.
        2. Set <Contents Type> attribute to "NBS-9".
        3. Send the following grouped request to FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-READ-ATTRIBUTES
            F-DESELECT
            F-END-GROUP
        4. Return the current directory name to the FTP client.
        5. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        6. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

8.1.18. QUIT

        1. If user is not logged in, proceed to step 5.
        2. If file transfer is in progress, send F-P-ABORT or
           F-U-ABORT to FTAM Responder.
        3. If file transfer is not in progress, send and F-TERMINATE
           to FTAM Responder.
        4. Return charge information to FTP Client.
        5. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        6. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

8.1.19. REIN

        1. Flush all I/O and account information.
        2. Allow all transfers in progress to be completed.
        3. Set all parameters to default values.
        4. Send F-CANCEL to FTAM Responder.
        5. Send the following grouped request to FTAM Responder.
            F-BEGIN-GROUP
            F-CLOSE
            F-DESELECT
            F-END-GROUP
        6. Leave the control connection open.
        7. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply

           code(s) to FTP Client.
        8. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. Typically followed by a USER command.

8.1.20. REST

        1. Send F-CHECK to FTAM Responder.
        2. Send F-RESTART to FTAM Responder.
        3. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        4. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Notes:
        a. Will only have affect on FTAM Responder if the restart
           functional unit is negotiated on F-INITIALIZE.
        b. Refer to ISO 8571-3 for additional subtleties of FTAM
           checkpoint and restart.

8.1.21. RETR

        1. Save current pathname by appending saved CWD string with
           <pathname> argument.  If no saved CWD string, proceed to
           step 9.
        2. Set <Contents Type> parameter to appropriate type of file.
        3. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-OPEN
            F-END-GROUP
        4. If file does not exist, proceed to step 9.
        5. Send F-READ to FTAM Responder.
        6. Loop reading F-DATA until F-DATA-END.  As data is received,
           write it to the FTP data connection.
        7. Send F-TRANSFER-END to FTAM Responder.
        8. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-CLOSE
            F-DESELECT
            F-END-GROUP
        9. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply

           code(s) to FTP Client.
        10. Translate FTP Client reply codes to equivalent FTAM <Action
            Result> and <Diagnostic> parameters and send parameters to
            FTAM Responder.

        Note:
        a. <pathname> argument is assumed to be a filename, relative
           to the currently saved CWD.
        b. CWD of the FTAM system must be defined prior to issuance of
           RETR.

8.1.22. RMD

        1. Return a 502 reply code (Command not implemented) to the
           FTP Client.

        Note:
        a. As indicated in the NIST Stable Implementation Agreements
           for FTAM [NIST92], creation or deletion of NBS-9 files is
           outside the scope of the agreements.

8.1.23. RNFR

        1. Save current pathname by appending saved CWD string with
           <pathname> argument.  If no saved CWD string, proceed to
           step 3.
        2. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
                Get <Filename> parameter value from RNFR <pathname>
           argument.
            F-DESELECT
            F-END-GROUP
        3. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        4. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. <pathname> argument is assumed to be a filename, relative
           to the currently saved CWD.
        b. Together with RNTO, this command causes a file to be
           renamed.
        c. CWD of the FTAM system must be defined prior to issuance of
           RNFR.

8.1.24. RNTO

        1. Save current pathname by appending saved CWD string with
           <pathname> argument.  If no saved CWD string, proceed to
           step 3.
        2. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-CHANGE-ATTRIBUTES
                Get <Filename> parameter from arguments provided by
                RNTO and previous RNFR.
            F-DESELECT
            F-END-GROUP
        3. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        4. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. <pathname> argument is assumed to be a filename, relative
           to the currently saved CWD.
        b. Together with RNFR, this command causes a file to be
           renamed.
        c. CWD of the FTAM system must be defined prior to issuance of
           RNTO.

8.1.25. SITE

        1. Save the specified destination address information.
        2. Set the <Called Presentation Address> parameter value equal
           to the <string> argument.  This parameter will be used when
           the F-INITIALIZE is sent to the FTAM Responder.
        3. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        4. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. The <string> argument to the SITE command may include a
           Distinguished Name or a User Friendly Name.

8.1.26. SMNT

        1. Return a 502 reply code to FTP Client.

        Note:
        a. Argument is ignored.

8.1.27. STAT

        1. Provide the gateway session status to the FTP Client.
        2. Return a 211 reply code to FTP Client.

        Note:
        a. Argument is ignored.

8.1.28. STOR

        1. Save current pathname by appending saved CWD string with
           <pathname> argument.  If no saved CWD string, proceed to
           step 11.
        2. Send the following grouped request to FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-READ-ATTRIBUTES
                Save <Contents Type> parameter value
            F-DESELECT
            F-END-GROUP
        3. If the <Contents Type> parameter returned with the F-READ-
           ATTRIBUTES indicates a directory,  proceed to step 11.
        4. Send the following grouped request to the FTAM responder.
            F-BEGIN-GROUP
            F-CREATE
                Set the <Override> parameter in the F-CREATE to
                "Delete and create with new attributes.".
            F-OPEN
            F-END-GROUP
        5. If the file existed, set the <Contents Type> parameter in
           the F-CREATE to match the F-READ-ATTRIBUTES.  If the file
           did not exist, set the <Contents Type> parameter to
           "FTAM-1".  If TYPE "Image" was previously requested, set
           the <Contents Type> parameter to "FTAM-3".
        6. Send F-WRITE, with <Bulk Data Transfer Specification, FADU
           Operation> parameter set to "File Extend", to FTAM Responder.
        7. Loop reading data from FTP data connection, sending the
           data in F-DATA PDUs until end-of-file on the FTP
           connection.
        8. Send F-DATA-END to FTAM Responder.
        9. Send F-TRANSFER-END to FTAM Responder.

        10. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-CLOSE
            F-DESELECT
            F-END-GROUP
        11. Translate FTAM Responder <Action Result> and <Diagnostic>
            parameters to equivalent FTP reply code(s) and send reply
            code(s) to FTP Client.
        12. Translate FTP Client reply codes to equivalent FTAM
            <Action Result> and <Diagnostic> parameters and send
            parameters to FTAM Responder.

        Note:
        a. <pathname> argument is assumed to be a filename, relative
           to the currently saved CWD.
        b. CWD of the FTAM system must be defined prior to issuance of
           STOR.

8.1.29. STOU

        1. Save current pathname by appending saved CWD string with
           <pathname> argument.  If no saved CWD string, proceed to
           step 11.
        2. Send the following grouped request to FTAM Responder.
            F-BEGIN-GROUP
            F-SELECT
            F-READ-ATTRIBUTES
                Save <Contents Type> parameter value
            F-DESELECT
            F-END-GROUP
        3. If the file already exists, proceed to step 12.
        4. If the <Contents Type> parameter returned with the F-READ-
           ATTRIBUTES indicates a directory, proceed to step 11.
        5. Send the following grouped request to the FTAM responder.
            F-BEGIN-GROUP
            F-CREATE
                Set the <Override> parameter in the F-CREATE to
                "Delete and create with new attributes.".
            F-OPEN
            F-END-GROUP
        6. If the file existed, set the <Contents Type> parameter in
           the F-CREATE to match the F-READ-ATTRIBUTES.  If the file
           did not exist, set the <Contents Type> parameter to
           "FTAM-1".  If TYPE "Image" was previously requested, set
           the <Contents Type> parameter to "FTAM-3".
        7. Send F-WRITE, with <Bulk Data Transfer Specification, FADU
           Operation> parameter set to "File Extend", to FTAM Responder.
        8. Loop reading data from FTP data connection, sending the

           data in F-DATA PDUs until end-of-file on the FTP
           connection.
        9. Send F-DATA-END to FTAM Responder.
        10. Send F-TRANSFER-END to FTAM Responder.
        11. Send the following grouped request to the FTAM Responder.
            F-BEGIN-GROUP
            F-CLOSE
            F-DESELECT
            F-END-GROUP
        12. Translate FTAM Responder <Action Result> and <Diagnostic>
            parameters to equivalent FTP reply code(s) and send reply
            code(s) to FTP Client.
        13. Translate FTP Client reply codes to equivalent FTAM
            <Action Result> and <Diagnostic> parameters and send
            parameters to FTAM Responder.

        Note:
        a. <pathname> argument is assumed to be a filename, relative
           to the currently saved CWD.
        b. Same as STOR, except the name of the created file must be
           unique in that directory.
        c. CWD of the FTAM system must be defined prior to issuance of
           STOU.

8.1.30. STRU

        1. If <structure code> argument is not "File", return 504
           reply code to FTP Client; Otherwise return 200 reply code
           to FTP Client.

8.1.31. SYST

        1. Return 502 reply code to FTP client.

8.1.32. TYPE

        1. If no <type code> argument is provided, set <Contents Type>
           parameter equal to "FTAM-1".
        2. If argument is provided, and equal to "ASCII", set <Contents
           Type> parameter to "FTAM-1".
        3. If argument is provided, and equal to "Image", set <Contents
           Type> parameter to "FTAM-3".
        4. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        5. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. Default to ASCII if no <type code> argument is provided.

8.1.33. USER

        1. Set <Initiator Identity> parameter for issuing F-INITIALIZE
           to FTAM Responder.
        2. If the destination address was specified in the Domain Name
           used to attach to the gateway, use it to set the value of
           the <Called Presentation Address> parameter of the
           to-be-issued F-INITIALIZE command.
        3. If the destination address is not known, check if it was
           specified in a previously issued SITE command.  If
           available, set <Called Presentation Address> parameter for
           issuing F-INITIALIZE to FTAM Responder.
        4. If the destination address is still not available, check if
           it is encoded in the user identity (e.g., user@host). If
           encoded, set <Called Presentation Address> parameter for
           issuing F-INITIALIZE to FTAM Responder using the "host"
           portion.
        5. If no destination address is available, proceed to step 7.
        6. Prompt user for password.
        7. Translate FTAM Responder <Action Result> and <Diagnostic>
           parameters to equivalent FTP reply code(s) and send reply
           code(s) to FTP Client.
        8. Translate FTP Client reply codes to equivalent FTAM <Action
           Result> and <Diagnostic> parameters and send parameters to
           FTAM Responder.

        Note:
        a. A USER command should be acceptable in any state.
        b. Multiple mechanisms are available for specifying the
           destination address: 1) Domain Name used in connecting to
           gateway (see section 4, Use of Gateway Services); 2) SITE
           command argument; and 3) user@host format.

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

           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

      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,

           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.

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

           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.

        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.

        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.

        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"

           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).

   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;           |

                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

      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

      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

      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

      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

      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.

   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

   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.

   [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.

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

 

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