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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 <Diagnostic> value with identifier 1011
(Lower layer failure), as well as any known <Further Details>.
Other error conditions are not addressed in this discussion.
5.1. FTP-Initiated Gateway Service
The set of state variables for the FTP-Initiated Gateway service
follow:
State Variable State Definition
----------------------------------------------------------------
FTP-I:Initial-State Initial state of FTP-Initiated Gateway
service.
Gateway is waiting for an FTP Client to
issue a USER command in order to
proceed with connection establishment
with remote FTAM Responder. If SITE or
ACCT commands are sent while waiting
for USER command, save arguments for
subsequent use.
FTP-I:Wait-for-PASS Gateway has already received USER
command from FTP Client, as well as
userid and destination host DN.
Gateway is waiting for the FTAM
Responder logon password.
FTP-I:Wait-for-PAddress Gateway has already received PASS
command from FTP Client. Gateway is
resolving the provided FTAM Responder's
address to a Presentation Address. The
provided address may be a Distinguished
Name, User Friendly Name, or Domain
Name. Resolution will typically be
done using X.500 directory services.
FTP-I:Wait-for-Connection Gateway has initiated a connection to
the FTAM Responder and is waiting for
notification as to whether or not the
logon is successful.
FTP-I:Wait-for-ClientCmd Connection exists between FTP Client
and FTAM Responder. Gateway is waiting
for next command or response from FTP
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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 <Called Presentation Address>,
userid in <Initiator Identity>, and password in <Filestore
Password>.
5.1.5. FTP-I:Wait-for-Connection --> FTP-I:Wait-for-NextMapping
1. Gateway receives <State Result> of "Success" .
2. Gateway sends 230 reply code (User Logged In) to FTP
Client.
5.1.6. FTP-I:Wait-for-ClientCmd --> FTP-I:Wait-for-RespondrCmd
1. Gateway receives command or response from FTP Client and
maps it to FTAM protocol, as defined in section 8.1.
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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 <Responding Presentation
Address> or in the "@host" portion of the <Initiator
Identity> parameter. The userid is in <Initiator
Identity>, and password is in <Filestore Password>
parameter.
5.2.2. FTAM-I:Wait-for-IPAddress --> FTAM-I:Wait-for-Connection
1. Gateway resolves received Domain Name, Distinguished Name,
or User Friendly Name of FTP Server to IP address.
2. Gateway sends USER to FTP Server.
3. Gateway sends PASS to FTP Server.
5.2.3. FTAM-I:Wait-for-Connection --> FTAM-I:Wait-for-NextMapping
1. Gateway receives 230 reply code (User Logged In) from FTP
Server.
2. Gateway sends <State Result> of "Success" to FTAM
Initiator.
5.2.4 FTAM-I:Wait-for-InitiatrCmd --> FTAM-I:Wait-for-ServerCmd
1. Gateway receives command or response from FTAM Initiator
and maps it to FTP protocol, as defined in section 8.2.
5.2.5. FTAM-I:Wait-for-ServerCmd --> FTAM-I:Wait-for-InitiatrCmd
1. Gateway receives command or response from FTP Server and
maps it to FTAM protocol, as defined in section 8.2.
5.2.6. FTAM-I:Wait-for-InitiatrCmd --> FTAM-I:Wait-for-INITIALIZE
1. Gateway receives F-CLOSE primitive from FTAM Initiator;
maps F-CLOSE as per Section 8.2.
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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 <Filename> file attribute, subject to local security and
access control. All other requested attributes need not be returned.
Systems supporting the NBS-9 document type shall make available an
NBS-9 document called 'DIRLIS'. This document can be used to obtain
a listing of files and their associated attributes from a remote
Filestore.
Mindel & Slaski [Page 18]
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