Draft FTP-FTAM Gateway Spec
Joshua L Mindel <mindel@netwrx1.nw1.com> Thu, 03 September 1992 22:15 UTC
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Subject: Draft FTP-FTAM Gateway Spec
To: IETF <ietf-osi@cs.wisc.edu>, Robert Cooney <cooney@wnyose.nctsw.navy.mil>, Rob Hagens <hagens@cs.wisc.edu>
Date: Thu, 03 Sep 1992 17:29:21 -0400
From: Joshua L Mindel <mindel@netwrx1.nw1.com>
Fax: : (703) 648-0016
Location: Washington, D.C. Metro Area
Message-Id: <9209031729.aa00755@netwrx1.NW1.COM>
(s10h(s12V
J. L Mindel
R. L. Slaski
Open Networks, Inc.
September 1992
Draft Internet Standard
FTP-FTAM Gateway Specification
1. Status of the Memo
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.
This specification has been proposed as a Request for Comments (RFC)
to ensure the widest possible distribution on the Internet. Only
through additional implementations and fieldings will the FTP-FTAM
gateway reach its optimal capacity as a resource during the
anticipated long term coexistence of the TCP/IP and OSI protocol
suites.
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.
1.1 Acknowledgments
The authors of this proposed 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 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).
Larry Friedman, Donna Vincent and Michael Resnick of Digital
Equipment Corporation provided valuable comments after reviewing this
document in draft form. Len Tabacchi and George Bradshaw of the
Defense Information Systems Agency (formerly the Defense
Communications Agency) supported the FTP-FTAM Gateway as part of the
DISA GOSIP Gateway Project.
1 (s10h(s12V
2. Table of Contents
1. Status of the Memo...........................................1
1.1 Acknowledgments ..........................................1
2. Table of Contents............................................2
3. Introduction.................................................3
3.1 Overview of Gateway Operation ............................4
3.2 User Interaction .........................................6
3.2.1 FTP Client.............................................6
3.2.2 FTAM Initiator.........................................6
3.2.3 Summary of User Interaction Requirements...............7
4. Gateway Architecture.........................................7
5. Network Naming and Addressing................................9
5.1 Server-Initiator Gateway Service .........................9
5.1.1 FTP Client Responsibility..............................9
5.1.2 Gateway Responsibility.................................10
5.2 Responder-Client Gateway Service .........................10
5.2.1 FTAM Initiator Responsibility..........................10
5.2.2 Gateway Responsibility.................................10
6. Gateway State Variables and Transitions......................11
6.1 Server-Initiator Gateway Service .........................11
6.2 Responder-Client Gateway Service .........................13
7. Document Type Support........................................14
7.1 Notes on NBS-9 ...........................................14
8. Functional Comparison of FTP and FTAM........................15
8.1 Document Type Support ....................................16
8.1.1 Notes on NBS-9.........................................16
8.2 Loss of Functionality ....................................17
9. Protocol Function and Representation Mappings................17
9.1 Server-Initiator Mappings ................................18
9.2 Responder-Client Mappings ................................31
10. Mapping between FTP Reply Codes and FTAM Parameters..........38
10.1 FTP Reply Codes to FTAM Parameters .......................39
10.2 FTAM Parameters to FTP Reply Codes .......................42
10.3 Future Mapping Problem ...................................45
10.4 Error Handling ...........................................45
11. Implementation and Configuration Guidelines..................46
11.1 Robustness ...............................................46
11.2 Well-Known TCP/IP Port ...................................46
11.3 Gateway Listener Processes ...............................46
11.4 Implementation Testing ...................................46
11.5 POSIX File Naming and Organization .......................46
12. Security Considerations......................................47
13. References...................................................47
14. Authors' Addresses...........................................48
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3. 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 bidirectional set of
mappings between the FTP and FTAM protocols. Since the protocols
have quite different command structures, the mappings between them
are not one-to-one.
Two important goals of the mappings are to:
1. Provide FTP users with as much emulated FTP capability on an
FTAM Responder as possible, and
2. 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 FTP over either OSI or
TCP/IP lower-layer services.
Ideas presented in this specification are based on lessons learned in
fielding the gateway on the MILNET 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]. 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.
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* Provide a formal specification for organizations wishing to
procure FTP-FTAM gateways.
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].
3.1 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. Server-Initiator Gateway Services
Utilized when an FTP Client contacts the FTP-FTAM gateway to
instigate a file transfer with an FTAM Responder.
2. Responder-Client 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 Server-Initiator Gateway Services.
Figure 1 illustrates the perspective of the application process in
the Server-Initiator service. Figure 2 illustrates that of the
Responder-Client service.
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TCP Host OSI Host
+--------------+ +------------------+
| FTP Client | | FTAM Responder |
+--------------+ +------------------+
| |
| |
| |
| FTP-FTAM Gateway |
| +--------------------------------+ |
+-- | FTP Server FTAM Initiator | --+
+--------------------------------+
Figure 1 - Server-Initiator Gateway Service
TCP Host OSI Host
+--------------+ +------------------+
| FTP Server | | FTAM Initiator |
+--------------+ +------------------+
| |
| |
| |
| |
| FTP-FTAM Gateway |
| +--------------------------------+ |
+-- | FTP Client FTAM Responder | --+
+--------------------------------+
Figure 2 - Responder-Client Gateway Service
5 (s10h(s12V
3.2 User Interaction
To initiate a file transfer from an FTP Client, the Client connects
to the Server-Initiator 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.
Similarly, to initiate a file transfer from an FTAM Initiator, the
Initiator connects to the Responder-Client 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.
For file transfers in either direction, the user must explicitly
connect to the gateway prior to specifying the destination host,
userid, and password. Sections 11.2 and 11.3 provide more thoughts
on gateway implementation techniques.
3.2.1 FTP Client
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" initiates the connection between the FTP Client and
the gateway. Once connected, the desired OSI filestore is identified
with a site command. As discussed in Section 5, Network Naming and
Addressing, the desired filestore can be identified by either its
Distinguished Name or a User Friendly Name that is resolved by the
Directory Services provider [Kille90]. The userid is passed via the
user command, and the password is passed via the pass command. If
the FTAM Responder requires a password, a password prompt should
appear after issuing the "user username" command.
3.2.2 FTAM Initiator
The logon sequence taken by an FTAM Initiator when initiating a file
transfer with an FTP Server is given below:
% ftam Distinguished-Name-of-FTAM Responder
ftam> user username@DNS-string
ftam> pass password
The "ftam Distinguished-Name-of-FTAM Responder" initiates the
connection between the FTAM Inititiator 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.
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3.2.3 Summary of User Interaction Requirements
As shown in the previous two logon sequence scenarios, the gateway
user does not have access to the gateway filesystem; he merely makes
use of the gateway login procedure to specify the ultimate
destination userid and password. The following steps are required to
utilize the gateway:
1. User must be aware that a gateway is required to reach the
destination FTP or FTAM host.
2. User must determine which gateway is most appropriate for their
respective source-destination pair.
3. User must 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.
A more desirable approach is to make the gateway transparent enough
so that the end user:
1. Need not know that a gateway is required.
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.
4. 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 Server-Initiator and Responder-Client
service sets.
+------------+ +-------------+
| FTP Host | | FTAM Host |
+------------+ +-------------+
| |
| |
| |
| |
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| +---------------------------------+ |
| | FTP - FTAM | |
| | Gateway Application | |
| |---------------------------------| |
| | FTP | FTAM | |
| |----------------+----------------| |
| | TCP/IP | TP4/et al | |
| +---------------------------------+ |
| /|\ /|\ |
| | | |
+------------+ +-------------+
Figure 3 - Gateway Protocol Stack
A fundamental aspect of this gateway architecture is that data is
mapped and transmitted immediately; i.e., no transferred file need
ever reside on the gateway file system. In the context of this
document, the term "filesystem" refers to the file access and
maintenance mechanisms provided by the operating system. This lack
of gateway filesystem interaction helps speed up the end-to-end data
transfer. Another speed-enhancing feature of this architecture is
that both the FTP and FTAM network connections can operate
simultaneously. Additional advantages include:
1. FTP and FTAM hosts require no modification to utilize gateway
services.
2. Users require no knowledge of the other protocol.
3. Gateway access control is not impaired (since users cannot
directly access the gateway filesystem).
4. No additional filesystem space is required on the gateway.
5. Interactive nature of protocols is preserved.
6. Users become aware of fatal errors immediately.
Disadvantages of this design include the initial coding effort
required to develop the gateway and the subsequent re-coding efforts
required to keep it current.
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5. Network Naming and Addressing
The network naming and addressing schemes used by FTP (Domain Names,
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 Domain Name in the Domain Name System (BIND distributed
name service or static host table) and its IP address. To initiate a
connection to an FTP Server, the FTP Client looks up a Domain Name in
either a Domain Name server 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.
5.1 Server-Initiator Gateway Service
The FTP Client uses the Server-Initiator gateway service to utilize
the resources of an FTAM Responder.
The FTP Client is responsible for providing the gateway with an
authoritative Distinguished Name, or a User Friendly Name [Kille90],
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.
5.1.1 FTP Client Responsibility
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 command.
For example, suppose an FTAM Responder had the following
Distinguished Name:
CountryName = "US"
Organization = "Open Networks"
CommonName = "netwrx1"
CommonName = "OSI file service"
The FTP user action will appear as:
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% ftp washdc1-osigw.navy.mil
ftp> site "c=US@o=Open Networks@cn=netwrx1@cn=file service"
ftp> user mindel
ftp> pass ***********
The "ftp washdc1-osigw.navy.mil" 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@cn=netwrx1@cn=file service". Alternatively, a User Friendly
Name, such as:
"netwrx1, Open Networks, us"
can be specified, enabling the following FTP user action:
The FTP User action would appear as:
% ftp washdc1-osigw.navy.mil
ftp> site "netwrx1, Open Networks, us"
ftp> user mindel
ftp> pass ***********
5.1.2 Gateway Responsibility
Upon receipt of a Distinguished Name or a User Friendly Name, the
Gateway FTAM Initiator should contact the OSI Directory (X.500 or
local static table), present the Distinguished Name or User Friendly
Name and request the Presentation address associated with that 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.
5.2 Responder-Client Gateway Service
The FTAM Initiator uses the Responder-Client gateway service to
utilize the resources of an FTP Server.
The FTAM Initiator is responsible for providing the gateway with an
authoritative Domain Name of the desired TCP/IP filestore. It is the
responsibility of the gateway to resolve this Domain Name to its
corresponding IP address.
5.2.1 FTAM Initiator Responsibility
Once connected to the gateway, the FTAM Initiator should identify the
desired FTP Server via the FTP Server's Domain Name. The Domain Name
concept is described in [RFC1101].
5.2.2 Gateway Responsibility
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The Gateway FTP Client 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.
Once the IP address is obtained, the gateway can attempt a connection
with the ultimate destination host represented by this IP address.
6. Gateway State Variables and Transitions
As described, the FTP-FTAM gateway provides two sets of services:
Server-Initiator and Responder-Client. Each service has its own
mutually exclusive set of state variables and transitions that
deterministically define the actions of the gateway.
Concerning error conditions, if a connection is dropped when the
gateway is in any state other than SI:Initial-State or RC:Initial-
State, then the gateway will issue a fatal error message to the host
with the remaining connection, and then drop that connection. If the
remaining host is an FTP Client, then the gateway will send an ABOR,
QUIT, and 426 reply code (Connection closed, transfer aborted). If
it is an FTAM Initiator, then the gateway will send an F-P-ABORT with
a <Diagnostic> value with identifier 1011 (Lower layer failure), as
well as any known <Further Details>.
Other error conditions are not addressed in this discussion.
6.1 Server-Initiator Gateway Service
The set of state variables for the Server-Initiator Gateway service
follow:
State Variable State Definition
----------------------------------------------------------------
SI:Initial-State Initial state of Server-Initiator
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.
SI: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 login password.
SI:Wait-for-PAddress Gateway has already received PASS
command from FTP Client. Gateway is
11 (s10h(s12V
resolving the FTAM Responder's
Distinguished Name to a Presentation
Address. DN resolution will typically
be done using X.500 directory services.
SI:Wait-for-Connection Gateway has initiated a connection to
the FTAM Responder and is waiting for
notification as to whether or not the
login is successful.
SI:Wait-for-NextMapping Connection exists between FTP Client
and FTAM Responder. Gateway maps
between FTP and FTAM as commands and
responses are received.
Each of the possible state transitions is provided in the remainder
of Section 6.1. For each state transition, the actions causing the
transition are listed.
6.1.1 SI:Initial-State --> SI:Initial-State
1. Gateway receives SITE or ACCT command from FTP Client. SITE
argument includes Distinguish Name of FTAM Responder.
6.1.2 SI:Initial-State --> SI:Wait-for-PASS
1. Gateway receives USER command from FTP Client. Arguments
include Distinguished Name of FTAM Responder and userid on FTAM
responder.
6.1.3 SI:Wait-for-PASS --> SI:Wait-for-PAddress
1. Gateway receives PASS command from FTP Client.
6.1.4 SI:Wait-for-PAddress --> SI:Wait-for-Connection
1. Gateway resolves Distinguished 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>.
6.1.5 SI:Wait-for-Connection --> SI:Wait-for-NextMapping
1. Gateway receives <State Result> of "Success" .
2. Gateway sends 230 reply code (User Logged In) to FTP Client.
6.1.6 SI:Wait-for-NextMapping --> SI:Wait-for-NextMapping
1. Gateway performs mappings between FTP and FTAM, as defined in
Section 9.1.
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6.1.7 SI:Wait-for-NextMapping --> SI:Wait-for-USER
1. Gateway receives QUIT command from FTP Client; maps QUIT as per
Section 9.1.
6.2 Responder-Client Gateway Service
The set of state variables for the Responder-Client Gateway service
follow:
State Variable State Definition
----------------------------------------------------------------
RC:Initial-State Initial state of Responder-Client
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.
RC:Wait-for-IPAddress Gateway has already received F-
INITIALIZE from FTAM Initiator.
Gateway typically resolves the Domain
Name to an IP address using the BIND
Domain Name Service.
RC:Wait-for-Connection Gateway has initiated a connection to
the FTP Server and is waiting for
notification as to whether or not the
login is successful.
RC:Wait-for-NextMapping Connection exists between FTAM
Initiator and FTP Server. Gateway maps
between FTAM and FTP as commands and
responses are received.
Each of the possible state transitions is provided in the remainder
of Section 6.2. For each state transition, the actions causing the
transition are listed.
6.2.1 RC:Initial-State --> RC: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.
6.2.2 RC:Wait-for-IPAddress --> RC:Wait-for-Connection
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1. Gateway resolves Domain Name of FTP Server to IP address.
2. Gateway sends USER to FTP Server.
3. Gateway sends PASS to FTP Server.
6.2.3 RC:Wait-for-Connection --> RC: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.
6.2.4 RC:Wait-for-NextMapping --> RC:Wait-for-NextMapping
1. Gateway performs mappings between FTAM and FTP, as defined in
Section 9.2.
6.2.5 RC:Wait-for-NextMapping --> RC:Wait-for-INITIALIZE
1. Gateway receives F-CLOSE primitive from FTAM Initiator; maps F-
CLOSE as per Section 9.2.
7. 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 Ustructured 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
7.1 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].
14 (s10h(s12V
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.
8. 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 strict 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.
15 (s10h(s12V
In contrast to the Client/Server model present in the FTP scheme,
FTAM is based on the Initiator/Responder model. The key distinction
is that once the FTAM Initiator has established a connection with a
remote host, either the Initiator or Responder can request services
of the other. In the FTP realm, the Client both initiates a
connection and requests all services.
The FTP Client knows the real properties of the remote host
filesystem. FTAM, in contrast, embraces a conceptual model of a
filesystem, labeled a virtual filestore model. The virtual filestore
is a collection of files, each of which has a name that uniquely
identifies it. Each file has a set of attributes, such as ownership
information and contents, which is the data associated with the file.
One file attribute is the <Contents Type> of the file, typically of
value "FTAM-1", "FTAM-3", or "NBS-9". The FTAM Initiator only knows
the properties of the corresponding Responder and virtual filestore,
not the real properties of the filesystem on the remote host.
8.1 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 Ustructured 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
8.1.1 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.
16 (s10h(s12V
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.
8.2 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 is not 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.
9. Protocol Function and Representation Mappings
The mappings presented are based upon the FTAM protocol
implementation as defined in Stable Implementation Agreements for
Open Systems Interconnection Protocols: Part 9 - FTAM Phase 2,
produced by the March 1992 Open Systems Environment Implementors'
Workshop [NIST92], and in [ISO8571-1], [ISO8571-2],[ISO8571-
3],[ISO8571-4], and [ISO8571-5]. The FTP protocol as defined in
Request for Comments [RFC959]. The mappings are strongly influenced
by the work of M. A. Wallace et. al. at NIST [NIST86] and John Scott
at MITRE [MITRE87].
At a minimum, the FTAM implementation in the FTP-FTAM gateway should
support Implementation Profiles T1 (Simple File Transfer) and M1
(Management), as defined in [NIST92]. These Implementation Profiles
correspond to the A/111 and A/13 Profiles of Standards Promotion and
Application Group in Europe, respectively [NIST92].
The FTP protocol functions that are addressed in these mappings
include:
ABOR ACCT ALLO APPE
CDUP CWD DELE HELP
LIST MKD MODE NLST
NOOP PASS PASV PORT
PWD QUIT REIN REST
RETR RMD RNFR RNTO
SITE SMNT STAT STOR
17 (s10h(s12V
STOU STRU SYST TYPE
USER
The FTAM protocol functions that are addressed in these mappings
include:
F-BEGIN-GROUP REQ F-CANCEL REQ
F-CHANGE-ATTRIBUTE REQ F-CHECK REQ
F-CLOSE REQ F-CREATE REQ
F-DATA PDU F-DATA-END REQ
F-DELETE REQ F-DESELECT REQ
F-END-GROUP REQ F-ERASE REQ
F-INITIALIZE REQ F-LOCATE REQ
F-OPEN REQ F-READ REQ
F-READ-ATTRIBUTE REQ F-RECOVER REQ
F-RESTART REQ F-SELECT REQ
F-TERMINATE REQ F-TRANSFER-END
F-P-ABORT REQ F-U-ABORT REQ
F-WRITE REQ
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 10.
POSIX file naming and organization conventions are assumed in these
mappings; i.e., files in the systems are assumed to be organized in a
hierarchical structure in which all of the non-terminal nodes are
directories and all of the terminal nodes are any other type of file.
The following terminology is used in the mapping specifications:
argument .......FTP Service Command argument, as used in [RFC959].
parameter ......FTAM Service Primitive parameters and attributes,
as enumerated in Tables 6, 50, and 51 of [ISO8571-
3].
The following notation is used in the mapping specifications:
Arguments and parameters are enclosed in angle brackets; e.g.
<Action Result>
Values of arguments and parameters are enclosed in quotation
marks; e.g. "Success"
FTP Service Commands and FTAM Primitives are in uppercase; e.g. F-
INITIALIZE
9.1 Server-Initiator Mappings
18 (s10h(s12V
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
Server-Initiator 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.
At a minimum, the gateway should support ASCII and 8 bit binary file
types. It should also support FTP File Stream Mode.
Section 9.1 shows the steps required to implement the Server-
Initiator gateway service.
9.1.1 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.
9.1.2 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.
19 (s10h(s12V
3. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply codes
to FTP Client.
4. Translate FTP Client reply codes to equivalent FTAM <Action
Result> and <Diagnostic> parameters and send parameters to FTAM
Responder.
Note:
a. The ACCT command will be effective with the next PASS command.
9.1.3 ALLO
1. Return a 200 reply code to FTP Client.
9.1.4 APPE
1. Save current pathname by appending saved CWD string with
<pathname> argument. If no saved CWD string, proceed to step
12.
2. Send the following grouped request to FTAM Responder.
F-BEGIN-GROUP
F-SELECT
F-READ-ATTRIBUTES
Save <Contents Type> parameter value
F-DESELECT
F-END-GROUP
3. If the <Contents Type> parameter value returned with the F-READ-
ATTRIBUTES has a value of "NBS-9", proceed to step 12.
4. Send the following grouped request to the FTAM responder.
F-BEGIN-GROUP
F-CREATE
Set the <Override> parameter in the F-CREATE to "Select Old
File".
F-OPEN
F-END-GROUP
5. If the file existed, set the <Contents Type> parameter in the F-
CREATE to match that returned by the F-READ-ATTRIBUTES.
6. If the file did not exist and no previous FTP TYPE "Image"
command was issued, then set the <Contents Type> parameter to
"FTAM-1";
Otherwise, set the <Contents Type> parameter to "FTAM-3".
7. Send F-WRITE, with <Bulk Data Transfer Specification, FADU
Operation> parameter set to "File Extend", to FTAM Responder.
8. Loop reading data from FTP data connection, sending the data in
F-DATA PDUs until end-of-file on the FTP connection.
9. Send F-DATA-END to FTAM Responder.
10. Send F-TRANSFER-END to FTAM Responder.
11. Send the following grouped request to the FTAM Responder.
F-BEGIN-GROUP
F-CLOSE
F-DESELECT
F-END-GROUP
20 (s10h(s12V
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.
9.1.5 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.
9.1.6 CWD
1. Save <pathname> argument as CWD string.
2. Set <Contents Type> parameter to "NBS-9".
3. Send the following grouped request to FTAM Responder.
F-BEGIN-GROUP
F-SELECT
F-DESELECT
F-END-GROUP
4. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
21 (s10h(s12V
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.
9.1.7 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.
9.1.8 HELP
1. If no <string> argument is provided, send helpful information
about the implementation of the gateway to the FTP Client. If
an argument is provided, send more specific information.
2. Return the FTP reply code 214 to the FTP Client.
9.1.9 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
22 (s10h(s12V
F-END-GROUP
4. If the <Contents Type> parameter of the F-READ-ATTRIBUTES is not
"NBS-9", then return the <Filename>, <Contents Type>, <Date/Time
of Last Modification>, and <Filesize> parameter values, obtained
with the previous F-READ-ATTRIBUTES, to the FTP data connection;
and proceed to step 8.
5. Send the following grouped request to the FTAM Responder.
F-BEGIN-GROUP
F-SELECT
F-OPEN
F-END-GROUP
6. Send F-READ to FTAM Responder.
7. Loop reading F-DATA until F-DATA-END. As data is received,
write the <Filename>, <Permitted Actions>, <Contents Type>, and
<Date/Time of Last Modification> parameter values from the PDU
to the FTP data connection.
8. Send F-TRANSFER-END to FTAM Responder.
9. Send the following grouped request to the FTAM responder.
F-BEGIN-GROUP
F-CLOSE
F-DESELECT
F-END-GROUP
10. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
11. Translate FTP Client reply codes to equivalent FTAM <Action
Result> and <Diagnostic> parameters and send parameters to FTAM
Responder.
Note:
a. Assume the <pathname> argument is relative to the saved CWD,
whether filename or directory specification.
b. CWD of the FTAM system must be defined prior to issuance of
LIST.
c. Transfers over data connection should be in ASCII.
e. If list of files with full directory/file specification is
received from FTAM Responder, then gateway should parse
list to strip off directory portion.
9.1.10 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.
9.1.11 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).
23 (s10h(s12V
9.1.12 NLST
1. If <pathname> argument is provided, use <pathname> argument as
<Filename> parameter value in F-SELECT issued in step 3.
2. If no argument is provided, use saved CWD value as <Filename>
parameter value in F-SELECT issued in step 3; If no CWD string
is saved and no argument is provided, proceed to step 9.
3. Set <Contents Type> parameter to "NBS-9".
4. Send the following grouped request to the FTAM Responder.
F-BEGIN-GROUP
F-SELECT
F-OPEN
F-END-GROUP
5. Send F-READ to FTAM Responder.
6. Loop reading F-DATA until F-DATA-END. As data is received,
write the filenames and other useful information from the PDU
to the FTP data connection.
7. Send F-TRANSFER-END to FTAM Responder.
8. Send the following grouped request to the FTAM responder.
F-BEGIN-GROUP
F-CLOSE
F-DESELECT
F-END-GROUP
9. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
10. Translate FTP Client reply codes to equivalent FTAM <Action
Result> and <Diagnostic>parameters and send parameters to FTAM
Responder.
Note:
a. As per RFC 959 (FTP), the NLST <pathname> argument is a
directory.
b. Assume the argument is relative to the saved CWD, whether
filename or directory specification.
c. CWD of the FTAM system must be defined prior to issuance of
NLST.
d. Transfers over data connection should be in ASCII.
e. Gateway should parse full directory/file specifications received
from FTAM Responder to strip off directory portion. This is
required to support the "FTP multiple get" function that pipes
NLST output to the STOR command.
9.1.13 NOOP
1. Return a 200 reply code to FTP Client.
9.1.14 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.
24 (s10h(s12V
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.
9.1.15 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.
9.1.16 PORT
1. Return a 200 reply code to FTP Client.
9.1.17 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.
9.1.18 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.
9.1.19 REIN
1. Flush all I/O and account information.
25 (s10h(s12V
2. Allow all transfers in progress to be completed.
3. Set all parameters to default values.
4. Send F-CANCEL to FTAM Responder.
5. Send the following grouped request to FTAM Responder.
F-BEGIN-GROUP
F-CLOSE
F-DESELECT
F-END-GROUP
6. Leave the control connection open.
7. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
8. Translate FTP Client reply codes to equivalent FTAM <Action
Result> and <Diagnostic>parameters and send parameters to FTAM
Responder.
Note:
a. Typically followed by a USER command.
9.1.20 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.
9.1.21 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
26 (s10h(s12V
F-CLOSE
F-DESELECT
F-END-GROUP
9. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
10. Translate FTP Client reply codes to equivalent FTAM <Action
Result> and <Diagnostic> parameters and send parameters to FTAM
Responder.
Note:
a. <pathname> argument is assumed to be a filename, relative to the
currently saved CWD.
b. CWD of the FTAM system must be defined prior to issuance of
RETR.
9.1.22 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.
9.1.23 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.
9.1.24 RNTO
27 (s10h(s12V
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.
9.1.25 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.
9.1.26 SMNT
1. Return a 502 reply code to FTP Client.
Note:
a. Argument is ignored.
9.1.27 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.
9.1.28 STOR
28 (s10h(s12V
1. Save current pathname by appending saved CWD string with
<pathname> argument. If no saved CWD string, proceed to
step 11.
2. Send the following grouped request to FTAM Responder.
F-BEGIN-GROUP
F-SELECT
F-READ-ATTRIBUTES
Save <Contents Type> parameter value
F-DESELECT
F-END-GROUP
3. If the <Contents Type> parameter returned with the F-READ-
ATTRIBUTES indicates a directory, proceed to step 11.
4. Send the following grouped request to the FTAM responder.
F-BEGIN-GROUP
F-CREATE
Set the <Override> parameter in the F-CREATE to "Delete and
create with new attributes.".
F-OPEN
F-END-GROUP
5. If the file existed, set the <Contents Type> parameter in the F-
CREATE to match the F-READ-ATTRIBUTES. If the file did not
exist, set the <Contents Type> parameter to "FTAM-1". If TYPE
"Image" was previously requested, set the <Contents Type>
parameter to "FTAM-3".
6. Send F-WRITE, with <Bulk Data Transfer Specification, FADU
Operation> parameter set to "File Extend", to FTAM Responder.
7. Loop reading data from FTP data connection, sending the data in
F-DATA PDUs until end-of-file on the FTP connection.
8. Send F-DATA-END to FTAM Responder.
9. Send F-TRANSFER-END to FTAM Responder.
10. Send the following grouped request to the FTAM Responder.
F-BEGIN-GROUP
F-CLOSE
F-DESELECT
F-END-GROUP
11. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
12. Translate FTP Client reply codes to equivalent FTAM <Action
Result> and <Diagnostic> parameters and send parameters to FTAM
Responder.
Note:
a. <pathname> argument is assumed to be a filename, relative to the
currently saved CWD.
b. CWD of the FTAM system must be defined prior to issuance of
STOR.
9.1.29 STOU
1. Save current pathname by appending saved CWD string with
<pathname> argument. If no saved CWD string, proceed to
step 11.
29 (s10h(s12V
2. Send the following grouped request to FTAM Responder.
F-BEGIN-GROUP
F-SELECT
F-READ-ATTRIBUTES
Save <Contents Type> parameter value
F-DESELECT
F-END-GROUP
3. If the file already exists, proceed to step 12.
4. If the <Contents Type> parameter returned with the F-READ-
ATTRIBUTES indicates a directory, proceed to step 11.
5. Send the following grouped request to the FTAM responder.
F-BEGIN-GROUP
F-CREATE
Set the <Override> parameter in the F-CREATE to "Delete and
create with new attributes.".
F-OPEN
F-END-GROUP
6. If the file existed, set the <Contents Type> parameter in the F-
CREATE to match the F-READ-ATTRIBUTES. If the file did not
exist, set the <Contents Type> parameter to "FTAM-1". If TYPE
"Image" was previously requested, set the <Contents Type>
parameter to "FTAM-3".
7. Send F-WRITE, with <Bulk Data Transfer Specification, FADU
Operation> parameter set to "File Extend", to FTAM Responder.
8. Loop reading data from FTP data connection, sending the data in
F-DATA PDUs until end-of-file on the FTP connection.
9. Send F-DATA-END to FTAM Responder.
10. Send F-TRANSFER-END to FTAM Responder.
11. Send the following grouped request to the FTAM Responder.
F-BEGIN-GROUP
F-CLOSE
F-DESELECT
F-END-GROUP
12. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
13. Translate FTP Client reply codes to equivalent FTAM <Action
Result> and <Diagnostic> parameters and send parameters to FTAM
Responder.
Note:
a. <pathname> argument is assumed to be a filename, relative to the
currently saved CWD.
b. Same as STOR, except the name of the created file must be unique
in that directory.
c. CWD of the FTAM system must be defined prior to issuance of
STOU.
9.1.30 STRU
1. If <structure code> argument is not "File", return 504 reply
code to FTP Client;
Otherwise return 200 reply code to FTP Client.
30 (s10h(s12V
9.1.31 SYST
1. Return 502 reply code to FTP client.
9.1.32 TYPE
1. If no <type code> argument is provided, set <Contents Type>
parameter equal to "FTAM-1".
2. If argument is provided, and equal to "ASCII", set <Contents
Type> parameter to "FTAM-1".
3. If argument is provided, and equal to "Image", set <Contents
Type> parameter to "FTAM-3".
4. Translate FTAM Responder <Action Result> and <Diagnostic>
parameters to equivalent FTP reply code(s) and send reply
code(s) to FTP Client.
5. Translate FTP Client reply codes to equivalent FTAM <Action
Result> and <Diagnostic> parameters and send parameters to FTAM
Responder.
Note:
a. Default to ASCII if no <type code> argument is provided.
9.1.33 USER
1. Set <Initiator Identity> parameter for issuing F-INITIALIZE to
FTAM Responder.
2. If destination was encoded in the user identity (e.g.,
user@host), set <Called Presentation Address> parameter for
issuing F-INITIALIZE to FTAM Responder.
3. If destination was not encoded in the user identity, then get
the destination address from the argument to the previously
issued SITE command. If no destination address is available,
proceed to step 5.
4. Prompt user for password.
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.
Note:
a. A USER command should be acceptable in any state.
b. If host not included in USER argument (that is, argument is not
in user@host format), then SITE command with destination host DN
should have been issued previously.
9.2 Responder-Client Mappings
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
Responder-Client service are:
31 (s10h(s12V
1. Accept an FTAM Initiator request at the FTAM Responder side of
the gateway.
2. Map the request to the (set of) corresponding FTP Client
function(s).
3. Acting as an FTP Client, send the FTP Client function(s) to the
FTP Server.
4. Accept information returned to the FTP Client side of the
gateway. This information originated at the FTP Server.
5. Map this returned information to a form understood by the FTAM
Responder side of the gateway.
6. Send this returned information from the FTAM Responder side of
the gateway to the FTAM Initiator.
At a minimum, the gateway should support the following FTAM document
types: FTAM-1 (unstructured text file), FTAM-3 (unstructured binary
file), and NBS-9 (set of directory entries).
Section 9.2 shows the steps required to implement the Responder-
Client gateway service. Where appropriate, each FTAM service
primitive is followed by those parameters that are relevant to the
mapping.
9.2.1 F-BEGIN-GROUP REQ
1. Send F-BEGIN-GROUP RESP PDU to FTAM Initiator signifying that
processes are available to handle concatenated requests.
9.2.2 F-CANCEL REQ
1. Close FTP data connection.
2. Send ABOR to FTP Server.
3. Translate FTP Server reply code to equivalent FTAM Responder
action and diagnostic parameters and send parameters to FTAM
Initiator via F-CANCEL RESP PDU.
4. Translate FTAM Initiator action and diagnostic parameters to
equivalent FTP reply codes and send reply codes to FTP
Server.
Note:
a. F-U-ABORT REQ is a viable alternative to F-CANCEL REQ.
b. Note that since ABOR is not implemented by all FTP Servers, the
remote file may be corrupted, though accessible.
9.2.3 F-CHANGE-ATTRIBUTE REQ
1. Get original filename from <Filename> parameter and send it with
an RNFR to the FTP Server.
32 (s10h(s12V
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.
9.2.4 F-CHECK REQ
1. Send an F-CHECK RESP PDU to the FTAM Initiator.
9.2.5 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.
9.2.6 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.
9.2.7 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.
33 (s10h(s12V
9.2.8 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.
9.2.9 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.
9.2.10 F-DESELECT REQ
1. Return F-DESELECT RESP PDU, with <Action Result> parameter value
of "Success", to FTAM Initiator.
9.2.11 F-END-GROUP REQ
1. Send STAT command sequence to FTP Server.
2. Translate FTP Server reply code to equivalent FTAM Responder
<Action Result> and <Diagnostic>
parameters and send parameters to FTAM Initiator via F-END GROUP
RESP.
3. Translate FTAM Initiator <Action Result> and <Diagnostic>
parameters to equivalent FTP reply codes and send reply codes to
FTP Server.
9.2.12 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.
9.2.13 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. Get ultimate destination address (FTP Server Domain Name) from
<Responding Presentation Address> parameter. If this parameter
34 (s10h(s12V
is null, look at the "@host" portion of the <Initiator Identity>
parameter.
4. Get userid from <Initiator Identity> and send it with USER
command to FTP Server.
5. Get password from <Filestore Password> and send it with PASS
command to FTP Server.
6. If necessary, send ACCT command to FTP Server.
7. Negotiate acceptance of mandatory functional units, service
classes, service types, presentation contexts, and attribute
groups.
8. Accept context management functional unit passed by Presentation
service provider.
9. 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
10. Translate FTAM Initiator <Action Result> and <Diagnostic>
parameters to equivalent FTP reply codes and send reply codes to
FTP Server.
9.2.14 F-LOCATE REQ
Note:
a. Not supported since FTAM-1 and FTAM-3 don't support this
primitive.
9.2.15 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.
9.2.16 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.
35 (s10h(s12V
4. If reply code from FTP Server is 1xx, open FTP data connection
and loop until End-of-File is read on FTP data connection.
Inside loop, read block from FTP data connection, format FTAM
DATA PDU, and send FTAM PDU to FTAM Initiator. At End-of-File
on FTP data connection, send F-DATA-END and return.
5. If reply code from FTP Server is not 1xx, send F-CANCEL REQ to
FTAM Initiator.
6. Translate FTP Server reply code to equivalent FTAM Responder
<Action Result> and <Diagnostic> parameters and send parameters
to FTAM Initiator via F-READ RESP PDU.
7. Translate FTAM Initiator <Action Result> and <Diagnostic>
parameters to equivalent FTP reply codes and send reply codes to
FTP Server.
Note:
a. To send NLST response, TYPE must be ASCII.
9.2.17 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.
9.2.18 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.
9.2.19 F-RESTART REQ
1. To interrupt any bulk data transfer in progress, send ABOR to
FTP Server.
2. To negotiate the point at which data transfer is to be
restarted, get <Checkpoint Identifier> parameter from FTAM
Initiator and send it with REST to FTP Server.
3. Translate FTP Server reply code to equivalent FTAM Responder
<Action Result> and <Diagnostic> parameters and send parameters
to FTAM Initiator via F-RESTART RESP PDU.
36 (s10h(s12V
4. Translate FTAM Initiator <Action Result> and <Diagnostic>
parameters to equivalent FTP reply codes and send reply codes to
FTP Server.
9.2.20 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
9.2.21 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.
9.2.22 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.
9.2.23 F-P-ABORT REQ
1. Send QUIT to FTP Server.
2. Return <Action Result> parameter value of "Permanent Error" to
FTAM Initiator.
3. Translate FTP Server reply code to equivalent FTAM Responder
<Action Result> and <Diagnostic> parameters and send parameters
to FTAM Initiator.
4. Translate FTAM Initiator <Action Result> and <Diagnostic>
parameters to equivalent FTP reply codes and send reply codes to
FTP Server.
9.2.24 F-U-ABORT REQ
37 (s10h(s12V
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.
9.2.25 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.
10. Mapping between FTP Reply Codes and FTAM Parameters
The focus of the protocol function and representation mappings,
presented in the previous sections, is on non-error encumbered
processing. Though appropriate responses are designated in many
cases, it is intended that a more thorough use of responses will be
incorporated into gateway implementations.
The purpose of this section is to provide a set of mappings between
FTAM responses (<Action Result> and <Diagnostic>) and FTP responses
(reply codes).
The <Action Result> parameter of the FTAM File Service primitives
conveys information which summarizes that available in the
<Diagnostic> parameter. The value is never less than the most severe
diagnostic value. The valid values of this parameter are "Success",
"Transient Error", and "Permanent Error". The FTP response text
should be supplied in the <Further Details> field of the
<Diagnostics> sequence in the FTAM response and abort messages.
An FTAM <Action Result> "Success" may be accompanied by a
<Diagnostic> with value of "Informative Error Type". These "Success"
diagnostic messages are associated with error type 0 in the table
below (and in [ISO8571-3]). Error type 1 indicates a transient
error, while type 2 indicates a permanent error.
An FTP reply consists of a three digit number followed by some text.
The number is defined as a 3-digit code, each digit of which has a
38 (s10h(s12V
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.
10.1 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. The
following abbreviations are used for FTAM action parameter values:
trans = transient error
perman = permanent error
39 (s10h(s12V
FTP Reply |FTAM Diagnostic
|
|
Code Text |Result Type Id
---------------------------------------------+------------------
110 Restart marker reply |success 0 0
120 Service ready in nnn minutes |success 0 0
125 Data connection open, transfer |
starting |success 0 0
150 File status okay; about to open |
data connection |success 0 0
200 Command okay |success 0 0
202 Command not implemented; |
superfluous |success 0 0
211 System status, or system help |
reply |success 0 0
212 Directory status |success 0 0
213 File status |success 0 0
214 Help message |success 0 0
215 NAME system type |success 0 0
220 Service ready for new user |success 0 0
221 Service closing control connection |success 0 0
225 Data connection; no transfer in |
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 login |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
40 (s10h(s12V
550 Requested action not taken; file |
unavailable (e.g., file not found, |
no access) |perman 2 3013
551 Requested action aborted, page |
type |perman 2 5002
552 Requested file action aborted, |
exceeded storage allocation |perman 2 9
553 Requested file action not taken, |
file name not allowed |perman 2 3024
41 (s10h(s12V
10.2 FTAM Parameters to FTP Reply Codes
This section presents the set of mappings between FTAM diagnostic
parameters and their equivalent FTP reply codes. 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 paramater type | 504
2 1006 Unsupported paramater types | 504
2 1007 FTAM protocol err., unspecific | 426
2 1008 FTAM protocol err., procedure err | 426
2 1009 FTAM protocol err., funct. unit err| 426
2 1010 FTAM protocol err., corruption err.| 426
2 1011 Lower layer failure | 426
1,2 1012 Lower layer addressing error | 426
1,2 1013 Timeout | 426
1,2 1014 System shutdown | 426
2 1015 Illegal grouping sequence | 503
2 1016 Grouping threshold violation | 503
2 1017 Inconsistent PDU request | 503
2 2000 Association with user not allowed | 532
2 2002 Unsupported service class | 504
0 2003 Unsupported functional unit | 211
42 (s10h(s12V
2 2003 Unsupported functional unit | 502
0 2004 Attribute group error, unspecific | 211
1,2 2004 Attribute group error, unspecific | 504
2 2005 Attribute group not supported | 504
0 2006 Attribute group not allowed | 211
2 2006 Attribute group not allowed | 504
0 2007 Bad account | 211
2 2007 Bad account | 532
0 2008 Association management, unspecific | 211
1,2 2008 Association management, unspecific | 532
2 2009 Association management, bad address| 532
1,2 2010 Association management, bad account| 532
0 2011 Checkpoint window error, too large | 211
2 2011 Checkpoint window error, too large | 426
0 2012 Checkpoint window error, too small | 211
2 2012 Checkpoint window error, too small | 426
0 2013 Checkpoint window error, unsupp. | 211
2 2013 Checkpoint window error, unsupp. | 504
0 2014 Communications QoS not supported | 211
1,2 2014 Communications QoS not supported | 504
2 2015 Initiator identity unacceptable | 532
0 2016 Context management refused | 211
0 2017 Rollback not available | 211
0 2018 Contents type list cut by |
responder | 211
0 2019 Contents type list by |
Presentation Service | 211
2 2020 Invalid filestore password | 530
2 2021 Incompatible service classes | 530
1,2 3000 Filename not found | 550
1,2 3001 Selection attributes not matched | 550
2 3002 Initial attributes not possible | 550
2 3003 Bad attribute name | 550
1,2 3004 Non-existent file | 550
1,2 3005 File already exists | 553
1,2 3006 File cannot be created | 553
1,2 3007 File cannot be deleted | 553
0 3008 Concurrency control not available | 211
2 3008 Concurrency control not available | 503
0 3009 Concurrency control not supported | 211
2 3009 Concurrency control not supported | 502
0 3010 Concurrency control not possible | 211
2 3010 Concurrency control not possible | 503
0 3011 More restrictive lock | 211
1 3011 More restrictive lock | 450
1,2 3012 File busy | 450
1,2 3013 File not available | 450
0 3014 Access control not available | 211
1,2 3014 Access control not available | 503
0 3015 Access control not supported | 211
1,2 3015 Access control not supported | 502
0 3016 Access control inconsistent | 211
1,2 3016 Access control inconsistent | 503
0 3017 Filename truncated | 211
43 (s10h(s12V
0 3018 Initial attributes altered | 211
1,2 3019 Bad account | 532
0 3020 Override selected existing file | 211
0 3021 Override deleted and recreated | 211
0 3022 Create override deleted and |
recreate file with new attributes | 211
1,2 3023 Create override, not possible | 553
1,2 3024 Ambiguous file specification | 553
2 3025 Invalid create password | 550
2 3026 Invalid delete password on override| 550
2 3027 Bad attribute value | 550
2 3028 Requested access violation | 550
2 3029 Functional unit not available for | 550
requested access |
0 3030 File created but not selected | 211
1 3030 Invalid create password | 550
0 4000 Attribute non-existent | 211
1,2 4000 Attribute non-existent | 501
1,2 4001 Attribute cannot be read | 504
1,2 4002 Attribute cannot be changed | 504
1,2 4003 Attribute not supported | 504
2 4004 Bad attribute name | 501
2 4005 Bad attribute value | 501
0 4006 Attribute partially supported | 211
0 4007 Additional set attribute value |
not distinct | 211
1,2 5000 Bad FADU, unspecific | 550
2 5001 Bad FADU, size error | 501
2 5002 Bad FADU, type error | 551
2 5003 Bad FADU, poorly specified | 501
2 5004 Bad FADU, bad location | 550
0 5005 FADU does not exist | 550
1 5005 FADU does not exist | 550
0 5006 FADU not available, unspecific | 550
1,2 5006 FADU not available, unspecific | 550
1,2 5007 FADU not available for reading | 550
1,2 5008 FADU not available for writing | 550
1,2 5009 FADU not available for location | 550
1,2 5010 FADU not available for erasure | 550
1,2 5011 FADU cannot be inserted | 550
1,2 5012 FADU cannot be replaced | 550
0 5013 FADU cannot be located | 550
1,2 5013 FADU cannot be located | 550
2 5014 Bad data element type | 550
1,2 5015 Operation not available | 500
1,2 5016 Operation not supported | 502
0 5017 Operation inconsistent | 211
2 5017 Operation inconsistent | 503
0 5018 Concurrency control not available | 211
1,2 5018 Concurrency control not available | 503
0 5019 Concurrency control not supported | 211
2 5019 Concurrency control not supported | 502
0 5020 Concurrency control inconsistent | 211
2 5020 Concurrency control inconsistent | 503
44 (s10h(s12V
0 5021 Processing mode not available | 211
1,2 5021 Processing mode not available | 503
0 5022 Processing mode not supported | 211
2 5022 Processing mode not supported | 504
0 5023 Processing mode inconsistent | 211
2 5023 Processing mode inconsistent | 503
0 5024 Access context not available | 211
2 5024 Access context not available | 503
0 5025 Access context not supported | 211
2 5025 Access context not supported | 504
1,2 5026 Bad write, unspecific | 550
1,2 5027 Bad read, unspecific | 550
0 5028 Local failure, unspecific | 211
1,2 5028 Local failure, unspecific | 451
0 5029 Local failure, filespace exhausted | 211
1,2 5029 Local failure, filespace exhausted | 552
0 5030 Local failure, data corrupted | 211
1,2 5030 Local failure, data corrupted | 451
0 5031 Local failure, data corrupted | 211
1,2 5031 Local failure, data corrupted | 451
2 5032 Future file size exceeded | 451
0 5034 Future file size increased | 211
0 5035 Functional unit invalid in |
processing mode | 211
2 5035 Functional unit invalid in |
processing mode | 503
0 5036 Contents type inconsistent | 211
2 5036 Contents type inconsistent | 503
0 5037 Contents type simplified | 211
0 5038 Duplicate FADU name | 211
1,2 5039 Damage to select/open regime | 553
1,2 5040 FADU locking not available on file | 450
1,2 5041 FADU locked by another user | 450
10.3 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 Responder-Client
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.
10.4 Error Handling
The minimal acceptable solution for Responder-Client 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 Server-Initiator service errors, the minimal acceptable solution
is to return reply code 221, "Service closing control connection,
Logged out if appropriate".
45 (s10h(s12V
11. 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.
11.1 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.
11.2 Well-Known TCP/IP Port
The Server-Initiator gateway process should 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 should be moved to another port that is known
to those users (e.g., System Administrators) requiring FTP-to-FTP
access to the gateway computer.
11.3 Gateway Listener Processes
To simplify the administrative overhead on the gateway computer
system, it is advisable to merge the Server-Initiator service and
Responder-Client gateway listener processes into a single executable
module. This single daemon would act as the one and only gateway
listener processes. As connections were established with hosts,
other processes would be created.
11.4 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].
11.5 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. POSIX file naming and organization
conventions are assumed; 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.
46 (s10h(s12V
12. Security Considerations
The gateway system places the burden of authentication on the
destination system. The authentication parameters of each protocol
are applied at the destination and no additional parameters are
needed for authentication at the gateway. As such, no gateway
password file is required to support gateway functions.
Additional gateway security can be maintained by employing standard
TCP access restrictions.
13. 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.
[KILLE90] Using the OSI Directory to achieve User Friendly Naming,
S.E. Kille, June 1990.
[MITRE87] An FTP/FTAM Application Bridge, An FTAM/FTAM (MTR-
87W00186), John A. Scott, The MITRE Corporation, July 1987.
[NETWRX90a] Gateway Technical Specification, Joshua L Mindel, Open
Networks, Inc. (formerly NetWorks One) 28 February 1990.
[NETWRX90b] FTP Gateway User's Guide, Joshua L Mindel, Open
Networks, Inc. (formerly NetWorks One) 28 February 1990.
47 (s10h(s12V
[NIST86] A Gateway Architecture Between FTP and FTAM (ICST/SNA86-6),
M.A. Wallace et al, National Institute of Standards and
Technology, U.S. Department of Commerce, July 1986.
[NIST91] CSL Bulletin: File Transfer, Access, and Management,
National Institute of Standards and Technology, U.S.
Chamber of Commerce, July 1991.
[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] File Transfer Protocol (FTP), Request for Comments 959,
John Postel and Joyce Reynolds, ISI, October 1985.
[RFC1101] DNS Encoding of Network Names and other Types, Request for
Comments 1101, P.V. Mockapetris, April 1989.
[ROSE90] The Open Book: A Practical Perspective on OSI, Marshall T.
Rose, Prentice-Hall Inc., 1990.
14. Authors' Addresses
Joshua L Mindel
Open Networks, Inc.
11490 Commerce Park Dr., Suite 205
Reston, Virginia 22091 USA
Phone: (703) 648-0013
E-mail: mindel@netwrx1.nw1.com
Robert L. Slaski
Open Networks, Inc.
11490 Commerce Park Dr., Suite 205
Reston, Virginia 22091 USA
Phone: (703) 648-0013
E-mail: slaski@netwrx1.nw1.com
48
- Draft FTP-FTAM Gateway Spec Joshua L Mindel
- Re: Draft FTP-FTAM Gateway Spec Steve Hardcastle-Kille