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rfc:rfc1415

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.

Mindel & Slaski [Page 1] RFC 1415 FTP-FTAM Gateway Specification January 1993

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

Mindel & Slaski [Page 2] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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.

Mindel & Slaski [Page 3] RFC 1415 FTP-FTAM Gateway Specification January 1993

  • 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.

Mindel & Slaski [Page 4] RFC 1415 FTP-FTAM Gateway Specification January 1993

        TCP Host                                  OSI Host
    +--------------+                        +------------------+
    |  FTP Client  |                        |  FTAM Responder  |
    +--------------+                        +------------------+
           |                                          |
           |                                          |
           |                                          |
           |            FTP-FTAM Gateway              |
           |    +--------------------------------+    |
           +--  |  FTP Server    FTAM Initiator  |  --+
                +--------------------------------+
           Figure 1  -  FTP-Initiated Gateway Service

Mindel & Slaski [Page 5] RFC 1415 FTP-FTAM Gateway Specification January 1993

        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.

Mindel & Slaski [Page 6] RFC 1415 FTP-FTAM Gateway Specification January 1993

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

Mindel & Slaski [Page 7] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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.

Mindel & Slaski [Page 8] RFC 1415 FTP-FTAM Gateway Specification January 1993

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

Mindel & Slaski [Page 9] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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:

Mindel & Slaski [Page 10] RFC 1415 FTP-FTAM Gateway Specification January 1993

         % 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:

Mindel & Slaski [Page 11] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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.

Mindel & Slaski [Page 12] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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,

Mindel & Slaski [Page 13] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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

Mindel & Slaski [Page 14] RFC 1415 FTP-FTAM Gateway Specification January 1993

                              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.

Mindel & Slaski [Page 15] RFC 1415 FTP-FTAM Gateway Specification January 1993

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.

Mindel & Slaski [Page 16] RFC 1415 FTP-FTAM Gateway Specification January 1993

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.

Mindel & Slaski [Page 17] RFC 1415 FTP-FTAM Gateway Specification January 1993

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.

Mindel & Slaski [Page 18] RFC 1415 FTP-FTAM Gateway Specification January 1993

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

Mindel & Slaski [Page 19] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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

Mindel & Slaski [Page 20] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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"

Mindel & Slaski [Page 21] RFC 1415 FTP-FTAM Gateway Specification January 1993

    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
  1. —————————————————————–
 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

Mindel & Slaski [Page 22] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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

Mindel & Slaski [Page 23] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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

Mindel & Slaski [Page 24] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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.

Mindel & Slaski [Page 25] RFC 1415 FTP-FTAM Gateway Specification January 1993

          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".

Mindel & Slaski [Page 26] RFC 1415 FTP-FTAM Gateway Specification January 1993

      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.

Mindel & Slaski [Page 27] RFC 1415 FTP-FTAM Gateway Specification January 1993

      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.

Mindel & Slaski [Page 28] RFC 1415 FTP-FTAM Gateway Specification January 1993

      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>

Mindel & Slaski [Page 29] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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.

Mindel & Slaski [Page 30] RFC 1415 FTP-FTAM Gateway Specification January 1993

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

Mindel & Slaski [Page 31] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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

Mindel & Slaski [Page 32] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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.

Mindel & Slaski [Page 33] RFC 1415 FTP-FTAM Gateway Specification January 1993

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.

Mindel & Slaski [Page 34] RFC 1415 FTP-FTAM Gateway Specification January 1993

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.

Mindel & Slaski [Page 35] RFC 1415 FTP-FTAM Gateway Specification January 1993

      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

Mindel & Slaski [Page 36] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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.

Mindel & Slaski [Page 37] RFC 1415 FTP-FTAM Gateway Specification January 1993

      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

Mindel & Slaski [Page 38] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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
  1. —————————————————————-
    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

Mindel & Slaski [Page 39] RFC 1415 FTP-FTAM Gateway Specification January 1993

    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,

Mindel & Slaski [Page 40] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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.

Mindel & Slaski [Page 41] RFC 1415 FTP-FTAM Gateway Specification January 1993

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

Mindel & Slaski [Page 42] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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.

Mindel & Slaski [Page 43] RFC 1415 FTP-FTAM Gateway Specification January 1993

      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.

Mindel & Slaski [Page 44] RFC 1415 FTP-FTAM Gateway Specification January 1993

      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.

Mindel & Slaski [Page 45] RFC 1415 FTP-FTAM Gateway Specification January 1993

      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"

Mindel & Slaski [Page 46] RFC 1415 FTP-FTAM Gateway Specification January 1993

         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).

Mindel & Slaski [Page 47] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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;           |

Mindel & Slaski [Page 48] RFC 1415 FTP-FTAM Gateway Specification January 1993

              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

Mindel & Slaski [Page 49] RFC 1415 FTP-FTAM Gateway Specification January 1993

    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

Mindel & Slaski [Page 50] RFC 1415 FTP-FTAM Gateway Specification January 1993

    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

Mindel & Slaski [Page 51] RFC 1415 FTP-FTAM Gateway Specification January 1993

    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

Mindel & Slaski [Page 52] RFC 1415 FTP-FTAM Gateway Specification January 1993

    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

Mindel & Slaski [Page 53] RFC 1415 FTP-FTAM Gateway Specification January 1993

    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.

Mindel & Slaski [Page 54] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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

Mindel & Slaski [Page 55] RFC 1415 FTP-FTAM Gateway Specification January 1993

 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.

Mindel & Slaski [Page 56] RFC 1415 FTP-FTAM Gateway Specification January 1993

 [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.

Mindel & Slaski [Page 57] RFC 1415 FTP-FTAM Gateway Specification January 1993

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

Mindel & Slaski [Page 58]

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