RFC 1415

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RFC 1415

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

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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.

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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

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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.

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RFC 1415 FTP-FTAM Gateway Specification January 1993

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

| FTP Host | | FTAM Host |

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

| |

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

| | FTP - FTAM | |

| | Gateway Application | |

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

| | FTP | FTAM | |

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

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

| /|\ /|\ |

| | | |

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

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

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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.

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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:

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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,

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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 value with identifier 1011
(Lower layer failure), as well as any known .

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

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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 ,
userid in , and password in .

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

1. Gateway receives 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.

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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.

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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 or in the "@host" portion of the parameter. The userid is in , and password is in
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 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.

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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 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.

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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

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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 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

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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.,

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

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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

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

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

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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

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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 and
parameters to equivalent FTP reply code(s) and send reply
codes to FTP Client.
4. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to
FTAM Responder.

8.1.2. ACCT

1. Set parameter value for issuing F-INITIALIZE to
FTAM Responder.
2. If , , and
parameters are available, attempt
connection with FTAM Responder;
Otherwise wait for additional ACCT commands.
3. Translate FTAM Responder and
parameters to equivalent FTP reply code(s) and send reply
codes to FTP Client.
4. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to

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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
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 parameter value
F-DESELECT
F-END-GROUP
3. If the 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 parameter in the F-CREATE to
"Select Old File".
F-OPEN
F-END-GROUP
5. If the file existed, set the 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 parameter
to "FTAM-1";
Otherwise, set the parameter to "FTAM-3".
7. Send F-WRITE, with 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.

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

Note:
a. 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 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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
5. Translate FTP Client reply codes to equivalent FTAM and 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 argument as CWD string.
2. Set parameter to "NBS-9".

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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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
5. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to
FTAM Responder.

Note:
a. The 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
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 and
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. 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 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.

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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 argument is provided, proceed to step 3.
2. Save current pathname by appending saved CWD string with
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 , , , and parameters
F-DESELECT
F-END-GROUP
4. If the parameter of the F-READ-ATTRIBUTES
is not "NBS-9", then return the , , , and
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 , , ,
and 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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
11. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to
FTAM Responder.

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

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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 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 argument is provided, use argument
as parameter value in F-SELECT issued in step 3.
2. If no argument is provided, use saved CWD value as
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 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 and

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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 and parameters and send parameters to
FTAM Responder.

Note:
a. As per RFC 959 (FTP), the NLST 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 parameter for F-INITIALIZE.
2. If , , and
are available, issue F- INITIALIZE to
FTAM Responder.
3. Translate FTAM Responder and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
4. Translate FTP Client reply codes to equivalent FTAM and 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.

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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 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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
6. Translate FTP Client reply codes to equivalent FTAM and 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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
6. Translate FTP Client reply codes to equivalent FTAM and 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 and
parameters to equivalent FTP reply code(s) and send reply

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RFC 1415 FTP-FTAM Gateway Specification January 1993

code(s) to FTP Client.
8. Translate FTP Client reply codes to equivalent FTAM and 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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
4. Translate FTP Client reply codes to equivalent FTAM and 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
argument. If no saved CWD string, proceed to
step 9.
2. Set 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 and
parameters to equivalent FTP reply code(s) and send reply

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code(s) to FTP Client.
10. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to
FTAM Responder.

Note:
a. 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
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 parameter value from RNFR
argument.
F-DESELECT
F-END-GROUP
3. Translate FTAM Responder and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
4. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to
FTAM Responder.

Note:
a. 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.

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RFC 1415 FTP-FTAM Gateway Specification January 1993

8.1.24. RNTO

1. Save current pathname by appending saved CWD string with
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 parameter from arguments provided by
RNTO and previous RNFR.
F-DESELECT
F-END-GROUP
3. Translate FTAM Responder and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
4. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to
FTAM Responder.

Note:
a. 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 parameter value equal
to the argument. This parameter will be used when
the F-INITIALIZE is sent to the FTAM Responder.
3. Translate FTAM Responder and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
4. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to
FTAM Responder.

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

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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
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 parameter value
F-DESELECT
F-END-GROUP
3. If the 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 parameter in the F-CREATE to
"Delete and create with new attributes.".
F-OPEN
F-END-GROUP
5. If the file existed, set the parameter in
the F-CREATE to match the F-READ-ATTRIBUTES. If the file
did not exist, set the parameter to
"FTAM-1". If TYPE "Image" was previously requested, set
the parameter to "FTAM-3".
6. Send F-WRITE, with 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.

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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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
12. Translate FTP Client reply codes to equivalent FTAM
and parameters and send
parameters to FTAM Responder.

Note:
a. 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
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 parameter value
F-DESELECT
F-END-GROUP
3. If the file already exists, proceed to step 12.
4. If the 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 parameter in the F-CREATE to
"Delete and create with new attributes.".
F-OPEN
F-END-GROUP
6. If the file existed, set the parameter in
the F-CREATE to match the F-READ-ATTRIBUTES. If the file
did not exist, set the parameter to
"FTAM-1". If TYPE "Image" was previously requested, set
the parameter to "FTAM-3".
7. Send F-WRITE, with parameter set to "File Extend", to FTAM Responder.
8. Loop reading data from FTP data connection, sending the

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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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
13. Translate FTP Client reply codes to equivalent FTAM
and parameters and send
parameters to FTAM Responder.

Note:
a. 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 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 argument is provided, set
parameter equal to "FTAM-1".
2. If argument is provided, and equal to "ASCII", set parameter to "FTAM-1".
3. If argument is provided, and equal to "Image", set parameter to "FTAM-3".
4. Translate FTAM Responder and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
5. Translate FTP Client reply codes to equivalent FTAM and parameters and send parameters to
FTAM Responder.

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RFC 1415 FTP-FTAM Gateway Specification January 1993

Note:
a. Default to ASCII if no argument is provided.

8.1.33. USER

1. Set 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 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 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 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 and
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
8. Translate FTP Client reply codes to equivalent FTAM and 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

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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

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

F-BEGIN-GROUP none

F-CANCEL ABOR

F-CHANGE-ATTRIBUTE RNFR, RNTO

F-CHECK none

F-CLOSE none

F-CREATE STOR

F-DATA ALLO, STOR or RETR or APPE

F-DATA-END none

F-DELETE DELE

F-DESELECT none

F-END-GROUP STAT

F-ERASE DELE

F-INITIALIZE ACCT, PASS, USER

F-LOCATE none

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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,

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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 parameter and send it
with an RNFR to the FTP Server.
2. Get new filename from 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 , ,
and 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 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 and parameters and
send parameters to FTAM Initiator.
3. Translate FTAM Initiator and
parameters to equivalent FTP reply codes and send reply
codes to FTP Server.

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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 and parameters and
send parameters to FTAM Initiator.
4. Translate FTAM Initiator and
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 and parameters and
send parameters to FTAM Initiator.
4. Translate FTAM Initiator and
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 and parameters and
send parameters to FTAM Initiator via F-DELETE RESP PDU.
3. Translate FTAM Initiator and
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 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 and
parameters and send parameters to FTAM Initiator via F-END

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RFC 1415 FTP-FTAM Gateway Specification January 1993

GROUP RESP.
3. Translate FTAM Initiator and
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 and parameters and
send parameters to FTAM Initiator via F-ERASE RESP PDU.
3. Translate FTAM Initiator and
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 , , and 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
parameter for the ultimate destination parameter.
5. If the ultimate destination address is still not known,
check if it is available in the parameter.
6. Get userid from and send it with USER
command to FTP Server.
7. Get password from 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 and parameters and
send parameters to FTAM Initiator via F-INIT RESP PDU.
12. Translate FTAM Initiator and
parameters to equivalent FTP reply codes and send reply
codes to FTP Server.

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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
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 and 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 and
parameters and send parameters to FTAM Initiator via F-OPEN
RESP PDU.
6. Translate FTAM Initiator and
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 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 is FTAM-1 or FTAM-3, then send RETR to
FTP Server.
3. If is "NBS-9", then send NLST to FTP
Server.
4. If reply code from FTP Server is 1xx, open FTP data
connection and loop until End-of-File is read on FTP data
connection. Inside loop, read block from FTP data
connection, format FTAM DATA PDU, and send FTAM PDU to FTAM
Initiator. At End-of-File on FTP data connection, send
F-DATA-END and return.

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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 and parameters and
send parameters to FTAM Initiator via F-READ RESP PDU.
7. Translate FTAM Initiator and
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 ,
, and parameter values
and return them to the FTAM Initiator.
3. Translate FTP Server reply code to equivalent FTAM
Responder and parameters and
send parameters to FTAM Initiator via F-READ-ATTRIBUTE RESP
PDU.
4. Translate FTAM Initiator and
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 and parameters and
send parameters to FTAM Initiator.
3. Translate FTAM Initiator and
parameters to equivalent FTP reply codes and send reply
codes to FTP Server.

Note:
a. Regime recovery is only possible if the 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 parameter from FTAM
Initiator and send it with REST to FTP Server.

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RFC 1415 FTP-FTAM Gateway Specification January 1993

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

8.2.20. F-SELECT REQ

1. Get 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 parameter sent by the FTAM
Initiator. If the access rights match, return parameter value of "Success", otherwise return
parameter value of "Failure".
3. Translate FTP Server reply code to equivalent FTAM
Responder and parameters and
send parameters to FTAM Initiator via F-SELECT RESP PDU.
4. Translate FTAM Initiator and
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 and parameters and
send parameters to FTAM Initiator via F-TERMINATE RESP PDU.
3. Translate FTAM Initiator and
parameters to equivalent FTP reply codes and send reply
codes to FTP Server.

8.2.22. F-TRANSFER-END

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

8.2.23. F-P-ABORT REQ

1. Send QUIT to FTP Server.
2. Return parameter value of "Permanent Error"

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RFC 1415 FTP-FTAM Gateway Specification January 1993

to FTAM Initiator.
3. Translate FTP Server reply code to equivalent FTAM
Responder and parameters and
send parameters to FTAM Initiator.
4. Translate FTAM Initiator and
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 parameter value of "Permanent Error"
to FTAM Initiator.
3. Translate FTP Server reply code to equivalent FTAM
Responder and parameters and
send parameters to FTAM Initiator.
4. Translate FTAM Initiator and
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
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
and parameters and send
parameters to FTAM Initiator.
6. Translate FTAM Initiator and
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 ( and ) and FTP responses
(reply codes).

Mindel & Slaski [Page 47]

RFC 1415 FTP-FTAM Gateway Specification January 1993

The parameter of the FTAM File Service primitives
conveys information which summarizes that available in the
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 field of the
sequence in the FTAM response and abort messages.

An FTAM "Success" may be accompanied by a
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 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

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RFC 1415 FTP-FTAM Gateway Specification January 1993

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.

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RFC 1415 FTP-FTAM Gateway Specification January 1993

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RFC 1415 FTP-FTAM Gateway Specification January 1993

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RFC 1415 FTP-FTAM Gateway Specification January 1993

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RFC 1415 FTP-FTAM Gateway Specification January 1993

9.3. Future Mapping Problem

At some point in the future, the FTAM 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 . 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 field. Similarly for
FTP-Initiated service errors, the minimal acceptable solution is to
return reply code 221, "Service closing control connection, Logged
out if appropriate". While this minimal solution is acceptable, the
recommended approach for Gateway developers is to implement the
mappings presented in Section 9.1, FTP Reply Codes to FTAM
Parameters, and Section 9.2, FTAM Parameters to FTP Reply Codes.

10. Implementation and Configuration Guidelines

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

10.1. Robustness

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

The gateway should support multiple concurrent FTP and FTAM
connections.

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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

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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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