Network Working Group D. Nash
Request for Comments: 2204 ODETTE
Category: Informational September 1997
ODETTE File Transfer Protocol
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Abstract
This memo describes a file transfer protocol to facilitate electronic
data interchange between trading partners.
The protocol, denoted the ODETTE File Transfer Protocol, supports
both direct communication between installations and indirect
communication via a third party clearing centre. It was developed by
the Organisation for Data Exchange by Tele Transmission in Europe to
facilitate communication within the European motor industry and is
presented here to allow for wider use within the Internet community.
Table of Contents
1. IntrodUCtion 3
1.1 - Background 3
1.2 - Relationship to the original ODETTE Standard 3
1.3 - General Principles 3
1.4 - Structure 4
1.5 - Virtual Files 4
1.6 - Service Description 7
2. Network Service (TCP Transport Service) 7
2.1 - Introduction 7
2.2 - Service Primitives 7
2.3 - Port Assignment 9
3. File Transfer Service 9
3.1 - Model 10
3.2 - Session Setup 11
3.3 - File Transfer 13
3.4 - Session Take Down 16
3.5 - Service State Automata 19
4. Protocol Specification 22
4.1 - Overview 22
4.2 - Start Session Phase 22
4.3 - Start File Phase 23
4.4 - Data Transfer Phase 26
4.5 - End File Phase 27
4.6 - End Session Phase 27
4.7 - Problem Handling 28
5. Commands and Formats 28
5.1 - Conventions 28
5.2 - Commands 29
5.3 - Command Formats 29
5.4 - Identification Code 45
6. ODETTE-FTP Data Exchange Buffer 46
6.1 - Overview 46
6.2 - Data Exchange Buffer Format 46
6.3 - Buffer Filling Rules 47
7. Stream Transmission Buffer (TCP only) 47
7.1 - Introduction 47
7.2 - Stream Transmission Header Format 49
8. Protocol State Machine 50
8.1 - ODETTE-FTP State Machine 50
8.2 - Error Handling 50
8.3 - States 51
8.4 - Input Events 53
8.5 - Output Events 54
8.6 - Local Variables 55
8.7 - Local Constants 55
8.8 - Session Connection State Table 56
8.9 - Error and Abort State Table 58
8.10 - Speaker State Table 1 59
8.11 - Speaker State Table 2 63
8.12 - Listener State Table 65
8.13 - Example 68
9. Security Considerations 68
Appendix A Virtual File Mapping Example 69
Appendix B ISO 646 Character Subset 72
Acknowledgements 73
References 73
ODETTE Address 74
Author's Address 74
1. Introduction
1.1 Background
The ODETTE File Transfer Protocol (ODETTE-FTP) was defined in 1986 by
working group four of the Organisation for Data Exchange by Tele
Transmission in Europe (ODETTE) to address the electronic data
interchange (EDI) requirements of the European automotive industry.
It was designed in the spirit of the Open System Interconnection
(OSI) model utilising the Network Service provided by the CCITT X25
recommendation.
Over the last ten years ODETTE-FTP has been widely deployed on
systems of all sizes from personal computers to large mainframes. As
a result of the wide scale deployment of internet technology and the
trend towards global business practices, ODETTE has decided to extend
the scope of it's file transfer protocol to allow the use of TCP/IP
and to make the protocol available to the Internet community.
This memo describes the ODETTE-FTP protocol using the Transmission
Control Protocol for it's network service.
1.2 Relationship to the original ODETTE Standard
This memo is an interpretation of version 1.3 of the ODETTE File
Transfer Protocol [OFTP]. In the event of any ambiguity between this
document and the original ODETTE-FTP, the original shall take
precedence.
For ODETTE-FTP on TCP/IP the following sections have been added with
respect to the original document.
Section 2 - Network Service
Section 7 - Stream Transmission Buffer
Appendix A - Virtual File mapping example
1.3 General Principles
The aim of the ODETTE-FTP is to facilitate the transmission of a file
between one or more locations in a way that is independent of the
data communication network, system hardware and software environment.
In designing and specifying the protocol, the following factors were
considered.
1. The possible differences of size and sophistication (file storage,
small and large systems).
2. The necessity to work with existing systems (reduce changes to
existing products and allow easy implementation).
3. Systems of different ages.
4. Systems of different manufactures.
5. The potential for growth in sophistication (limit impact and avoid
changes at other locations).
1.4 Structure
ODETTE-FTP is modelled on the OSI reference model. It is designed to
use the Network Service provided by level 3 of the model and provide
a File Service to the users. Thus the protocol spans levels 4 to 7
of model.
The description of the ODETTE-FTP contained in this memo is closely
related to the original 'X.25' specification of the protocol and in
the spirit of the OSI model describes:
1. A File Service provided to a user monitor.
2. A protocol for the exchange of information between peer
ODETTE-FTP entities.
A major consideration in adapting the protocol to use the
Transmission Control Protocol (TCP) was the desire to make no changes
to the existing protocol by adding the functionality required to
allow implementors to support internet communication with only minor
changes to existing ODETTE-FTP engines. To this end an additional
header has been added to the start of each exchange buffer to allow
the TCP byte stream to be broken up into the discrete exchange
buffers eXPected by the ODETTE-FTP protocol.
1.5 Virtual Files
Information is always exchanged between ODETTE-FTP entities in a
standard representation called a Virtual File. This allows data
transfer without regard for the nature of the communicating systems.
The mapping of a file between a local and virtual representation will
vary from system to system and is not defined here.
o---------o
Site Local
A File A
o---------o
o----------------------- Mapping A ------------------------o
o---------o
Virtual
File
o---------o
o------------------------------------------------o
ODETTE-FTP
o------------------------------------------------o
o---------o o---------o
Virtual Virtual
File File
o---------o o----+----o
o------ Mapping B ------------------------ Mapping C ------o
o---------o o----+----o
Local Site Site Local
File B B C File C
o---------o o---------o
A Virtual File is described by a set of attributes identifying and
defining the data to be transferred. The main attributes are:
1.5.1 Organisation:
Sequential
Logical records are presented one after another. The ODETTE-FTP
must be aware of the record boundaries.
1.5.2 Identification
Dataset Name
Dataset name of the Virtual File being transfered, assigned by
bilateral agreement.
Time stamp (HHMMSS)
A file qualifier indicating the time the Virtual File was made
available for transmission.
Date stamp (YYMMDD)
A file qualifier indicating the date the Virtual File was made
available for transmission.
The Dataset Name, Date and Time attributes are assigned by a Virtual
File's Originator and are used to uniquely identify the file. They
must not be changed by intermediate locations.
The Date attribute represents the decade and year in a two digit
field. Since the ODETTE-FTP only uses this information to identify a
particular Virtual File it will continue to operate correctly in the
year 2000 and beyond.
The User Monitor may use the Virtual File Date attribute in local
processes involving date comparisons and calculations. Any such use
falls outside the scope of this protocol and year 2000 handling is a
local implementation issue.
1.5.3 Record Format
Four record formats are defined.
Fixed (F)
Each record in the file has the same length.
Variable (V)
The records in the file can have different lengths.
Unstructured (U)
The file contains a stream of data. No structure is defined.
Text File (T)
A Text File is defined as a sequence of ASCII characters,
containing no control characters except CR/LF which delimits
lines. A line will not have more than 2048 characters.
1.5.4 Restart
ODETTE-FTP can negotiate the restart of an interrupted Virtual File
transmission. Fixed and Variable format files are restarted on
record boundaries. For Unstructured and Text files the restart
position is expressed as a file offset in 1K (1024 octet) blocks.
The restart position is always calculated relative to the Virtual
File.
1.6 Service Description
ODETTE-FTP provides a file transfer service to a user monitor and in
turn uses the Internet transport layer stream service to communicate
between peers.
These services are specified in this memo using service primitives
grouped into four classes as follows:
Request (RQ) An entity asks the service to do some work.
Indication (IND) A service informs an entity of an event.
Response (RS) An entity responds to an event.
Confirm (CF) A service informs an entity of the response.
Services may be confirmed, using the request, indication, response
and confirm primitives, or unconfirmed using just the request and
indication primitives.
2. Network Service (TCP Transport Service)
2.1 Introduction
ODETTE-FTP peer entities communicate with each other via the OSI
Network Service or the Transmission Control Protocol Transport
Service [TCP]. This is described by service primitives representing
request, indication, response and confirmation actions.
For the internet environment, the service primitives mentioned below
for the Network Service have to be mapped to the respective Transport
Service primitives. This section describes the network service
primitives used by ODETTE-FTP and their relationship to the TCP
interface. In practice the local transport service application
programming interface will be used to Access the TCP service.
2.2 Service Primitives
All Network primitives can be directly mapped to the respective
Transport primitives when using TCP.
2.2.1 Network Connection
N_CON_RQ ------> N_CON_IND
N_CON_CF <------ N_CON_RS
This describes the setup of a connection. The requesting ODETTE-FTP
peer uses the N_CON_RQ primitive to request an active OPEN of a
connection to a peer ODETTE-FTP, the Responder, which has previously
requested a passive OPEN. The Responder is notified of the incoming
connection via N_CON_IND and accepts it with N_CON_RS. The requester
is notified of the completion of it's OPEN request upon receipt of
_CON_CF.
Parameters
Request Indication Response Confirmation
---------------------------------------------------------------------
Dest addr ------> same same same
2.2.2 Network Data
N_DATA_RQ ------> N_DATA_IND
Data exchange is an unconfirmed service. The Requester passes data
for transmission to the network service via the N_DATA_RQ primitive.
The Responder is notified of the availability of data via N_DATA_IND.
In practice the notification and receipt of data may be combined,
such as by the return from a blocking read from the network socket.
Parameters
Request Indication
---------------------------------------------------------------------
Data ------------------> same
2.2.3 Network Disconnection
N_DISC_RQ ------> N_DISC_IND
An ODETTE-FTP requests the termination of a connection with the
N_DISC_RQ service primitive. It's peer is notified of the CLOSE by a
N_DISC_IND event. It is recognised that each peer must issue a
N_DISC_RQ primitive to complete the TCP symmetric close procedure.
2.2.4 Network Reset
------> N_RST_IND
An ODETTE-FTP entity is notified of a network error by a N_RST_IND
event. It should be noted that N_RST_IND would also be generated by
a peer RESETTING the connection, but this is ignored here as N_RST_RQ
is never sent to the Network Service by ODETTE-FTP.
2.3 Port Assignment
A ODETTE-FTP requester will select a suitable local port.
The responding ODETTE-FTP will listen for connections on Registered
Port 3305, the service name is 'odette-ftp'.
3. File Transfer Service
The File Transfer Service describes the services offered by an
ODETTE-FTP Entity to it's User Monitor. The implementation of the
service primitives is a local matter.
3.1 Model
o-------------------o o-------------------o
USER MONITOR USER MONITOR
o-------------------o o-------------------o
A A
..................... FILE TRANSFER SERVICE .....................
F_XXX_RQ/RS F_XXX_IND/CF F_XXX_RQ/RS F_XXX_IND/CF
V V
o-------------------o o-------------------o
- - - - - - >
ODETTE-FTP Entity E-Buffer ODETTE-FTP Entity
< - - - - - -
o-------------------o o-------------------o
A A
N_XXX_RQ/RS N_XXX_IND/CF N_XXX_RQ/RS N_XXX_IND/CF
........................ NETWORK SERVICE ........................
V V
o---------------------------------------------------------o
N E T W O R K
o---------------------------------------------------------o
Key: E-Buffer - Exchange Buffer
F_ - File Transfer Service Primitive
N_ - Network Service Primitive
3.2 Session Setup
3.2.1 Session Connection Service
F_CONNECT_RQ ---->----------------> F_CONNECT_IND
F_CONNECT_CF <----------------<---- F_CONNECT_RS
Parameters
Request Indication Response Confirm
---------------------------------------------------------------------
called-address -> same --- ----
calling-address-> same --- ----
ID1 ------------> same ID2 ------------> same
PSW1------------> same PSW2 -----------> same
mode1 ----------> mode2 ----------> mode3 ----------> same
restart1 -------> same -----------> restart2 -------> same
---------------------------------------------------------------------
Mode
Specifies the file transfer capabilities of the entity sending or
receiving a F_CONNECT primitive for the duration of the session.
Value:
Sender-Only The entity can only send files.
Receiver-Only The entity can only receive files.
Both The entity can both send and receive files.
Negotiation:
Sender-Only Not negotiable.
Receiver-Only Not negotiable.
Both Can be negotiated down to Sender-Only or
Receiver-Only by the User Monitor or the
ODETTE-FTP entity.
Request Indication Response Confirm
---------------------------------------------------------------------
Sender-only ----> Receiver-only --> Receiver-only --> Sender-only
Receiver-only --> Sender-only ----> Sender-only ----> Receiver-only
Both -----+-----> Both ----+------> Both -----------> Both
or +------> Receiver-only --> Sender-only
or +------> Sender-only ----> Receiver-only
or +-----> Receiver-only --> Receiver-only --> Sender-only
or +-----> Sender-only ----> Sender-only ----> Receiver-only
---------------------------------------------------------------------
Restart
Specifies the file transfer restart capabilities of the User
Monitor.
Value:
Negotiation:
Request Indication Response Confirm
---------------------------------------------------------------------
restart = Y ----> restart = Y --+-> restart = Y ----> restart = Y
or +-> restart = N ----> restart = N
restart = N ----> restart = N ----> restart = N ----> restart = N
---------------------------------------------------------------------
3.3 File Transfer
3.3.1 File Opening
F_START_FILE_RQ ---->----------------> F_START_FILE_IND
F_START_FILE_CF(+-) <----------------<---- F_START_FILE_RS(+-)
Parameters:
Request Ind. RS(+) CF(+) RS(-) CF(-)
--------------------------------------------------------------------
file-name ----> same ---- ---- ---- ----
date-time ----> same ---- ---- ---- ----
destination---> same ---- ---- ---- ----
originator----> same ---- ---- ---- ----
rec-format----> same ---- ---- ---- ----
rec-size -----> same ---- ---- ---- ----
file-size-----> same ---- ---- ---- ----
restart-pos1--> same-> restart-pos2-> same ---- ----
---- ---- ---- ---- cause ------> same
---- ---- ---- ---- retry-later-> same
--------------------------------------------------------------------
Notes:
1. Retry-later has values "Y" or "N". 2. Cause is the reason for
refusing the transfer (1,..,13,99). 3. Restart-pos1 not equal 0 is
only valid if restart has been agreed
during initial negotiation.
4. Restart-pos2 is less than or equal to restart-pos1.
3.3.2 Data Regime
F_DATA_RQ ---->----------------> F_DATA_IND
Notes:
1. The data format within a F_DATA primitive is locally defined.
2. The File Transfer service may have to provide a flow control
mechanism to regulate the flow of F_DATA primitives.
3.3.3 File Closing
F_CLOSE_FILE_RQ --->----------------> F_CLOSE_FILE_IND
F_CLOSE_FILE_CF(+-) <---------------<---- F_CLOSE_FILE_RS(+-)
Parameters
Request Ind RS(+) CF(+) RS(-) CF(-)
---------------------------------------------------------------------
rec-count ---> same ---- ---- ---- ----
unit-count --> same ---- ---- ---- ----
---- ---- Speaker=Y ---> Speaker=N ---- ----
---- ---- Speaker=N ---> Speaker=Y ---- ----
---- ---- ---- ---- cause ---> same
---------------------------------------------------------------------
In a positive Close File response (F_CLOSE_FILE_RS(+)) the current
Speaker may either:
1. Set Speaker to "Yes" and become the Speaker. 2. Set Speaker
to "No" and remain the Listener.
The File Transfer service will ensure that the setting of the speaker
parameter is consistent with the capabilities of the peer user.
The turn is never exchanged in the case of a negative response or
confirmation.
Only the Speaker is allowed to issue F_XXX_FILE_RQ primitives.
3.3.4 Exchanging the Turn
3.3.4.1 Initial Turn (First Speaker)
The Initiator becomes the first Speaker at the end of the Session
Setup (F_CONNECT_CF received by Initiator and F_CONNECT_RS sent by
Responder).
3.3.4.2 Following Turns
Rules:
1. At each unsuccessful End of File the turn is not exchanged.
2. At each successful End of File the turn is exchanged if requested
by the Listener:
- The current Listener receives F_CLOSE_FILE_IND
(Speaker = choice).
- If the Listener answers F_CLOSE_FILE_RS(Speaker = YES), it
becomes Speaker, the Speaker receives F_CLOSE_FILE_CF (Speaker =
NO) and becomes Listener.
- If the Listener answers F_CLOSE_FILE_RS(Speaker = NO), it
remains Listener, and the Speaker receives F_CLOSE_FILE_CF
(Speaker = YES) and remains Speaker.
3. The Speaker can issue a Change Direction request (F_CD_RQ) to
become the Listener. The Listener receives a Change Direction
indication (F_CD_IND) and becomes the Speaker.
4. In order to prevent loops of F_CD_RQ/IND, it is an error to send
F_CD_RQ immediately after having received a F_CD_IND.
3.3.5 End to End Response
This service is initiated by the current Speaker (if there is no file
transfer in progress) to send an End-to-End response from the final
destination to the originator of a file.
F_EERP_RQ ---->----------------> F_EERP_IND
Parameters
Request Indication
------------------------------------
filename -------> same
date -----------> same
time -----------> same
destination ----> same
originator -----> same
------------------------------------
Relationship with Turn:
- Only the Speaker may send an End to End Response request.
- Invoking the EERP service does not change the turn.
- If a F_CD_IND has been received just before F_EERP_RQ is issued,
this results in leaving the special condition created by the
reception of F_CD_IND; i.e. while it was possible to issue
F_RELEASE_RQ and not possible to issue F_CD_RQ just after the
reception of F_CD_IND, after having issued F_EERP_RQ the normal
Speaker status is entered again (F_CD_RQ valid, but F_RELEASE_RQ
not valid).
3.4 Session Take Down
3.4.1 Normal Close
F_RELEASE_RQ ---->----------------> F_RELEASE_IND
Parameters
Request Indication
---------------------------------------------------------------------
reason = normal -------> ----
---------------------------------------------------------------------
The Release service can only be initiated by the Speaker.
The Speaker can only issue a Release request (F_RELEASE_RQ) just
after receiving an unsolicited Change Direction indication
(F_CD_IND). This ensures that the other partner doesn't want to send
any more files in this session.
Peer ODETTE-FTP entities action a normal session release by
specifying Reason = Normal in an End Session (ESID) command.
3.4.2 Abnormal close
F_RELEASE_RQ ---->----------------> F_ABORT_IND
Parameters
Request Indication
---------------------------------------------------------------------
reason = error value --> same (or equivalent)
AO (Abort Origin) = (L)ocal or (D)istant
---------------------------------------------------------------------
Abnormal session release can be initiated by either the Speaker or
the Listener and also by the user or provider.
Abnormal session release can occur at any time within the session.
Peer ODETTE-FTP entities action an abnormal session release by
specifying Reason = Error-value in an End Session (ESID) command.
The abnormal session release deals with the following types of error:
1. The service provider will initiate an abnormal release in the
following cases:
1. Protocol error, 2. Failure of the Start Session (SSID)
negotiation, 3. Command not recognised, 4. Exchange buffer size
error, 5. Resources not available, 6. Other unspecified abort code
(with "REASON" = unspecified).
2. The User Monitor will initiate an abnormal release in the
following cases:
1. Local site emergency close down, 2. Resources not available, 3.
Other unspecified abort code (with "REASON" = unspecified).
Other error types may be handled by an abort of the connection.
3.4.3 Abort
F_ABORT_RQ ---->----------------> F_ABORT_IND
User Initiated Abort
F_ABORT_IND <--------------------> F_ABORT_IND
Provider Initiated Abort
Parameters
Request Indication
---------------------------------------------------------------------
-- R (Reason): specified or unspecified
-- AO (Abort Origin): (L)ocal or (D)istant
---------------------------------------------------------------------
The Abort service may be invoked by either entity at any time.
The service provider may initiate an abort in case of error
detection.
3.4.4 Explanation of Session Take Down Services
User OFTP Network OFTP User
----------------------------------------------------------------
1. Normal Release
F_RELEASE_RQ ESID(R=normal) F_RELEASE_IND
*---------------> =========================> ---------------->
(R=normal)
2. User Initiated Abnormal Release
F_RELEASE_RQ ESID(R=error) F_ABORT_IND
*---------------> =========================> --------------->
(R=error value) (R=error,AO=D)
User OFTP Network OFTP User
----------------------------------------------------------------
3. Provider Initiated Abnormal Release
F_ABORT_IND ESID(R=error) F_ABORT_IND
<---------------* *========================> ---------------->
4. User Initiated Connection Abort
F_ABORT_RQ N_DISC_RQ F_ABORT_IND
*---------------> ----------->..-----------> ---------------->
N_DISC_IND (R=unsp.,AO=D)
5. Provider Initiated Connection Abort
F_ABORT_IND N_DISC_RQ F_ABORT_IND
<---------------* *---------->..-----------> ---------------->
(R=error,AO=L) N_DISC_IND (R=unsp.,AO=D)
Key: * Origin of command flow
F_ ---> File Transfer Service primitive
N_ ---> Network Service primitive
===> ODETTE-FTP (OFTP) protocol message
3.5 Service State Automata
This state automata defines the service as viewed by the User
Monitor. Events causing a state transition are shown in lower case
and the resulting action in upper case where appropriate.
3.5.1 Idle State Diagram
o------------o
decision f_connect_ind
+----------------- IDLE -----------------+
F_CONNECT_RQ (0) F_CONNECT_RS
o------------o
V
o-----------------o
I_WF_FCONNECTCF
o--------+--------o
F_CONNECT_CF
V V
o-----------------o o-----------------o
IDLE SPEAKER IDLE LISTENER
(1) (2)
See Speaker See Listener
State Diagram State Diagram
o-----------------o o-----------------o
3.5.2 Speaker State Diagram
o-----------------o o-----------------o
IDLE LISTENER IDLE
CD_RQ just sent see (0)
see (3), Listen Idle
State Diagram State Diagram
o-----------------o o-----------------o
A A
decision decision decision
F_CD_RQ +----------------+ F_RELEASE_RQ
F_EERP_RQ
o=================o o-----------------o
<-------------+ IDLE SPEAKER
IDLE SPEAKER (4)
(1) decision CD_IND
<----------------------------- just received
o=================o F_EERP_RQ o-----------------o
A A
decision and P1 decision and P1
+-----------------+ +---------------------+
F_START_FILE_RQ F_START_FILE_RQ
V V
o---------------o
f_file_start_cf(-)
+---------------------- OPENING
o---------------o
f_file_close_cf(-) f_start_file_cf(+)
and not P2
V
o---------------o o---------------o
------------------+
CLOSING DATA TRANSFER record to send
<-----------------+
o---------------o o---------------o F_DATA_RQ
A
end of file
+-------------------+
F_CLOSE_FILE_RQ
o-----------------o
f_close_file(+) and P2 IDLE LISTENER
+---------------------------------------------> see (2), Listen
State Diagram
Predicates: o-----------------o
P1: Mode = Both or (Mode = Sender-Only)
P2: Negative confirmation or (positive confirmation, Speaker = YES)
3.5.3 Listener State Diagram
o-----------------o o-----------------o
IDLE SPEAKER IDLE
CD_IND just
received see(4) see (0)
Speaker State Idle
Diagram State Diagram
o-----------------o o-----------------o
A A
decision f_eerp_ind decision
F_CD_IND +--------------+ F_RELEASE_IND
o=================o o-----------------o
<-----------+ f_eerp_ind
<----------------------------- IDLE LISTENER
IDLE LISTENER (3)
f_start_file_ind CD_RQ
(2) and not p2 just sent
---------------------+
o=================o F_START_FILE_RS(-) o-----------------o
A A A
+-----------------------+
f_start_file_ind and not p2
+--------------------------------------+
F_START_FILE_RS(-)
f_start_file_ind f_start_file_ind
and p2 and p2
+-------------------------------+ +------------------+
F_START_FILE_RS(+) F_START_FILE_RS(+)
V V
o---------------o
f_close_file_ind and not p1 DATA -------------+
+------------------------------ TRANSFER
F_CLOSE_FILE_RS(-) <------------+
o---------------o F_DATA_IND
o---------------o
IDLE SPEAKER f_close_file_ind and p1
see (1), Spkr <--------------------------+
State Diagram F_CLOSE_FILE_RS(+)
o---------------o
Predicates:
P1: (decision to send F_CLOSE_FILE_RS(+)) and
(decision to set Speaker = yes in F_CLOSE_FILE_RS(+))
P2: (decision to send F_START_FILE_RS(+))
4. Protocol Specification
4.1 Overview
The ODETTE-FTP protocol is divided into five operating phases.
Start Session
Start File
Data Transfer
End File
End Session
After the End File phase an ODETTE-FTP entity may enter a new Start
File phase or terminate the session via the End Session phase.
ODETTE-FTP peers communicate by sending and receiving messages in
Exchange Buffers via the Network Service. Each Exchange Buffer
contains one of the following commands.
SSRM Start Session Ready Message
SSID Start Session
SFID Start File
SFPA Start File Positive Answer
SFNA Start File Negative Answer
DATA Data
CDT Set Credit
EFID End File
EFPA End File Positive Answer
EFNA End File Negative Answer
ESID End Session
CD Change Direction
EERP End to End Response
RTR Ready To Receive
The remainder of this section describes the protocol flows. Section
five details the command formats.
4.2 Start Session Phase
The Start Session phase is entered immediately after the network
connection has been established.
4.2.1 Entity Definition
The ODETTE-FTP entity that took the initiative to establish the
network connection becomes the Initiator. It's peer becomes the
Responder.
4.2.2 Protocol Sequence
The first message must be sent by the Responder.
1. Initiator <-------------SSRM -- Responder Ready Message
-- SSID ------------> Identification
<------------ SSID -- Identification
4.3 Start File Phase
4.3.1 Entity Definition
The Initiator from the Start Session phase is designated the Speaker
while the Responder becomes the Listener. The roles are reversed by
the Speaker sending a Change Direction command to the Listener.
4.3.2 Protocol Sequence
1. Speaker -- SFID ------------> Listener Start File
<------------ SFPA -- Answer YES
2. Speaker -- SFID ------------> Listener Start File
<------------ SFNA -- Answer NO
Go To 1
Note: The User Monitor should take steps to prevent a loop
situation occurring.
2. Speaker -- CD --------------> Listener Change Direction
Listener <------------ EERP -- Speaker End to End Response
-- RTR -------------> Ready to Receive
<------------ SFID -- Start File
4.3.3 Restart Facilities
The Start File command includes a count allowing the restart of an
interrupted transmission to be negotiated. If restart facilities are
not available the restart count must be set to zero. The sender will
start with the lowest record count + 1.
4.3.4 Broadcast Facilities
The destination in a Start File command can be specified as follows.
1. An explicitly defined destination.
2. A group destination that allows an intermediate location to
broadcast the Virtual File to multiple destinations.
The Listener will send a negative answer to the Speaker when the
destination is not known.
4.3.5 Priority
The prioritisation of files for transmission is left to the local
implementation. To allow some flexibility, a change direction
mechanism is available in the End File phase.
4.3.6 End To End Response (EERP)
The End to End Response (EERP) command notifies the originator of a
Virtual File that it has been successfully delivered to it's final
destination. This allows the originator to perform house keeping
tasks such as deleting copies of the delivered data.
A Response Command must be sent from the location performing the
final processing or distribution of the data to the originator. The
Response is mandatory and may be sent in the same or in any
subsequent session.
When an intermediate location broadcasts or distributes a Virtual
File it must receive a Response command from all the locations to
which it forwarded the data before sending it's own Response. This
ensures that the Response received by the Virtual File's originator
accounts for all the destination locations. An intermediate location
therefore needs to track the status of files it processes over time.
Example: Point to Point
Location A sends file Ba to Location B which will send an EERP to
location A after it successfully receives the file.
o----------o o-----------o
Loc. A ----------- S1 ----------> Loc. B
[Ba] <---------- R2 ----------- [Ba]
+----------o o-----------o
Key:
S - File Transfer R - Response EERP [Ba] - File for B from A
Example: Data distribution
Location A sends a Virtual File containing data for distribution to
locations B and C via clearing centres E1 and E2. Clearing centre E1
must wait for a response from E2 (for file Ba) and location C before
it sends it's response, R8, to location A. Clearing centre E2 can
only send response R7 to E1 when location B acknowledges file Ba with
response R6.
o---------o o---------o o---------o o---------o
Loc. A -- S1 -> Loc. E1 -- S2 -> Loc. E2 -- S5 -> Loc. B
[Ba,Ca] <- R8 -- [Ba,Ca] <- R7 -- [Ba] <- R6 -- [Ba]
o---------o o---------o o---------o o---------o
A
o---------o
+----- S3 -> Loc. C
+--------- R4 -- [Ca]
o---------o
Example: Data collection
Locations A and B send files Ca and Cb to clearing centre E1 which
forwards both files to location C in a single Virtual File. When it
receives response R4 from C, clearing centre E1 sends response R5 to
location A and R6 to location B.
o---------o o---------o o---------o
Loc. A -- S1 -> Loc. E1 -- S3 -> Loc. C
[Ca] <- R5 -- [Ca,Cb] <- R4 -- [Ca,Cb]
o---------o o---------o o---------o
A
o---------o
Loc. B -- S2 -----+
[Cb] <- R6 ---------+
o---------o
4.3.7 Ready To Receive Command (RTR)
In order to avoid congestion between two adjacent nodes caused by a
continuous flow of EERP's, a Ready To Receive (RTR) command is
provided. The RTR acts as an EERP acknowledgement for flow control
but has no end-to-end significance.
Speaker -- EERP ------------> Listener End to End Response
<------------- RTR -- Ready to Receive
-- EERP ------------> End to End Response
<------------- RTR -- Ready to Receive
-- SFID ------------> Start File
or
-- CD --------------> Exchange the turn
After sending an EERP, the Speaker must wait for an RTR before
sending any other commands.
4.4 Data Transfer Phase
Virtual File data flows from the Speaker to the Listener during the
Data Transfer phase which is entered after the Start File phase.
4.4.1 Protocol Sequence
To avoid congestion at the protocol level a flow control mechanism is
provided via the Credit (CDT) command.
A Credit limit is negotiated in the Start Session phase, this
represents the number of Data Exchange Buffers that the Speaker may
send before it is obliged to wait for a Credit command from the
Listener.
The available credit is initially set to the negotiated value by the
Start File positive answer, which acts as an implicit Credit command.
The Speaker decreases the available credit count by one for each data
buffer sent to the Listener.
When the available credit is exhausted, the Speaker must wait for a
Credit command from the Listener otherwise a protocol error will
occur and the session will be aborted.
The Listener should endeavour to send the Credit command without
delay to prevent the Speaker blocking.
1. Speaker -- SFID ------------> Listener Start File
<------------ SFPA -- Answer YES
2. If the Credit Value is set to 2
Speaker -- Data ------------> Listener Start File
-- Data ------------>
<------------- CDT -- Set Credit
-- Data ------------>
-- EFID ------------> End File
4.5 End File Phase
4.5.1 Protocol Sequence
The Speaker notifies the Listener that it has finished sending a
Virtual File by sending an End File (EFID) command. The Listener
replies with a positive or negative End File command and has the
option to request a Change Direction command from the Speaker.
1. Speaker -- EFID ------------> Listener End File
<------------ EFPA -- Answer YES
2. Speaker -- EFID ------------> Listener End File
<------------ EFPA -- Answer YES + CD
-- CD --------------> Change Direction
Listener <------------ EERP -- Speaker End to End Response
-------------- RTR -> Ready to Receive
Go to Start File Phase
3. Speaker -- EFID ------------> Listener End File
<------------ EFNA -- Answer NO
4.6 End Session Phase
4.6.1 Protocol Sequence
The Speaker terminates the session by sending an End Session (ESID)
command.
1. Speaker -- EFID ------------> Listener End File
<------------ EFPA -- Answer YES
-- CD --------------> Change Direction
Listener <------------ ESID -- Speaker End Session
4.7 Problem Handling
Error detection and handling should be done as close as possible to
the problem. This aids problem determination and correction. Each
layer of the reference model is responsible for it's own error
handling.
ODETTE-FTP can detect protocol errors through the construction of
it's state machine, and uses activity timers to detect session hang
conditions. These mechanisms are separate from the End to End
controls.
4.7.1 Protocol Errors
If a protocol error occurs the session will be terminated and
application activity aborted. Both locations enter the IDLE state.
4.7.2 Timers
To protect against application and network hang conditions ODETTE-FTP
uses activity timers for all situations where a response is required.
The timers and actions to be taken if they expire are described in
section 8, the Protocol State Machine.
4.7.3 Clearing Centres
The use of clearing centres introduces the possibility of errors
occurring as a result of data processing activities within the
centre. Such errors are not directly related to ODETTE-FTP or the
communication network and are therefore outside the scope of this
specification.
5. Commands and Formats
ODETTE-FTP entities communicate via Exchange Buffers. The Command
Exchange Buffers are described below. Virtual File data is carried
in Data Exchange Buffers which are described in Section 6.
5.1 Conventions
5.1.1 Representation unit:
The basic unit of information is an octet, containing eight bits.
5.1.2 Values and Characters:
The ISO 646 IRV 7-bit coded character set [ISO-646] is used to encode
constants and strings within command exchange buffers.
5.2 Commands
A Command Exchange Buffer contains a single command starting at the
beginning of the buffer. Commands and data are never mixed within an
Exchange Buffer. Each command has a fixed length and can not be
compressed.
Components:
1. Command identifier:
The first octet of an Exchange Buffer is the Command Identifier
and defines the format of the buffer.
2. Parameter(s):
Command parameters are stored in fixed fields within a Command
Exchange Buffer. All values are required.
5.3 Command Formats
The ODETTE-FTP commands are described below using the following
definitions.
Position (Pos.)
Field offset within the command exchange buffer, relative to a
zero origin.
Field
The name of the field.
Description
A description of the field.
Format
F - A field containing fixed values. All allowable values for
the field are enumerated in the command definition.
V - A field with variable values within a defined range. For
example the SFIDFSIZ field may contain any integer value
between 0000000 and 9999999.
X(n) - An alphanumeric field of length n octets.
9(n) - A numeric field of length n octets.
All attributes are in character format.
A String contains alphanumeric characters from the following set:
The numerals: 0 to 9
The upper case letters: A to Z
The following special set: / - . & ( ) space.
Space is not allowed as an embedded character.
Numeric fields are always right justified and left padding with
zeros must be done when needed.
5.3.1 SSRM - Start Session Ready Message
o-------------------------------------------------------------------o
SSRM Start Session Ready Message
Start Session Phase Initiator <---- Responder
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 SSRMCMD SSRM Command, 'I' F X(1)
1 SSRMMSG Ready Message, 'ODETTE FTP READY ' F X(17)
18 SSRMCR Carriage Return F X(1)
o-------------------------------------------------------------------o
SSRMCMD Command Code Character
Value: 'I' SSRM Command identifier.
SSRMMSG Ready Message String(17)
Value: 'ODETTE FTP READY '
SSRMCR Carriage Return Character
Value: Character with hex value '0D' or '8D'.
5.3.2 SSID - Start Session
o-------------------------------------------------------------------o
SSID Start Session
Start Session Phase Initiator <---> Responder
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 SSIDCMD SSID Command 'X' F X(1)
1 SSIDLEV Protocol Release Level F 9(1)
2 SSIDCODE Initiator's Identification Code V X(25)
27 SSIDPSWD Initiator's PassWord V X(8)
35 SSIDSDEB Exchange Buffer Size V 9(5)
40 SSIDSR Send / Receive Capabilities (S/R/B) F X(1)
41 SSIDCMPR Compression Indicator (Y/N) F X(1)
42 SSIDREST Restart Indicator (Y/N) F X(1)
43 SSIDSPEC Special Logic Indicator (N) F X(1)
44 SSIDCRED Credit V 9(3)
47 SSIDRSV1 Reserved F X(5)
52 SSIDUSER User Data V X(8)
60 SSIDCR Carriage Return F X(1)
o-------------------------------------------------------------------o
SSIDCMD Command Code Character
Value: 'X' SSID Command identifier.
SSIDLEV Protocol Release Level Numeric(1)
Value: '1' ODETTE-FTP protocol release level 1.
Future release levels will have higher numbers. The
protocol release level is negotiable, with the lowest level
being selected.
SSIDCODE Initiator's Identification Code String(25)
Format: See Identification Code (Section 5.4)
Uniquely identifies the Initiator (sender) participating
in the ODETTE-FTP session.
SSIDPSWD Password String(8)
Key to authenticate the sender. Assigned by bilateral
agreement.
SSIDSDEB Exchange Buffer Size Numeric(5)
Minimum: 128
Maximum: 99999
The length, in octets, of the largest Exchange Buffer that
can be accepted by the location. The length includes the
command octet but does not include the Stream Transmission
Header.
After negotiation the smallest size will be selected.
SSIDSR Send / Receive Capabilities Character
Value: 'S' Location can only send files.
'R' Location can only receive files.
'B' Location can both send and receive files.
Sending and receiving will be serialised during the
session, so parallel sessions will not take place.
An error occurs if adjacent locations both specify the send
or receive capability.
SSIDCMPR Compression Indication Character
Value: 'Y' The location can handle compressed data.
'N' The location can not handle compressed data.
Compression is only used if supported by both locations.
The compression mechanism is described in Section 6.2
SSIDREST Restart Indication Character
Value: 'Y' The location can handle the restart of a partially
transmitted file.
'N' The location can not restart a file.
SSIDSPEC Special Logic Indication Character
Value: 'N' Only valid value for TCP.
The Special Logic extensions are only useful in an X.25
environment and are not supported for TCP/IP.
SSIDCRED Credit Numeric(3)
Maximum: 999
The number of consecutive Data Exchange Buffers sent by the
Speaker before it must wait for a Credit (CDT) command from
the Listener.
The credit value is only applied to Data flow in the Data
Transfer phase.
The Speaker's available credit is initialised to SSIDCRED
when it receives a Start File Positive Answer (SFPA)
command from the Listener. It is zeroed by the End File
(EFID) command.
After negotiation, the smallest size must be selected in
the answer of the Responder, otherwise a protocol error
will abort the session.
Negotiation of the "credit-window-size" parameter.
Window Size m -- SSID ------------>
<------------ SSID -- Window Size n
(n less or equal m)
Note: negotiated value will be "n".
SSIDRSV1 Reserved String(5)
This field is reserved for future use.
SSIDUSER User Data String(8)
May be used by the ODETTE-FTP in any way. If unused it
should be initialised to spaces. It is expected that a
bilateral agreement exists as to the meaning of the data.
SSIDCR Carriage Return Character
Value: Character with hex value '0D' or '8D'.
5.3.3 SFID - Start File
o-------------------------------------------------------------------o
SFID Start File
Start File Phase Speaker ----> Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 SFIDCMD SFID Command, 'H' F X(1)
1 SFIDDSN Virtual File Dataset Name V X(26)
27 SFIDRSV1 Reserved F X(9)
36 SFIDDATE Virtual File Date stamp, (YYMMDD) V X(6)
42 SFIDTIME Virtual File Time stamp, (HHMMSS) V X(6)
48 SFIDUSER User Data V X(8)
56 SFIDDEST Destination V X(25)
81 SFIDORIG Originator V X(25)
106 SFIDFMT File Format, (F/V/U/T) F X(1)
107 SFIDLRECL Maximum Record Size V 9(5)
112 SFIDFSIZ File Size, 1K blocks V 9(7)
119 SFIDREST Restart Position V 9(9)
o-------------------------------------------------------------------o
SFIDCMD Command Code Character
Value: 'H' SFID Command identifier.
SFIDDSN Virtual File Dataset Name String(26)
Dataset name of the Virtual File being transferred,
assigned by bilateral agreement.
No general structure is defined for this attribute.
See Virtual Files - Identification (Section 1.5.2)
SFIDRSV1 Reserved String(9)
This field is reserved for future use.
SFIDDATE Virtual File Date stamp String(6)
Format: 'YYMMDD' 6 decimal digits representing the year, month
and day respectively [ISO-8601].
Date stamp assigned by the Virtual File's Originator
indicating when the file was made available for
transmission.
See Virtual Files - Identification (Section 1.5.2)
SFIDTIME Virtual File Time stamp String(6)
Format: 'HHMMSS' 6 decimal digits representing hours, minutes
and seconds respectively [ISO-8601].
Time stamp assigned by the Virtual File's Originator
indicating when the file was made available for
transmission.
See Virtual Files - Identification (Section 1.5.2)
SFIDUSER User Data String(8)
May be used by the ODETTE-FTP in any way. If unused it
should be initialised to spaces. It is expected that a
bilateral agreement exists as to the meaning of the data.
SFIDDEST Destination String(25)
Format: See Identification Code (Section 5.4)
The Final Recipient of the Virtual File.
This is the location that will look into the Virtual File
content and perform mapping functions. It is also the
location that creates the End to End Response (EERP)
command for the received file.
SFIDORIG Originator String(25)
Format: See Identification Code (Section 5.4)
Originator of the Virtual File.
It is the location that created (mapped) the data for
transmission.
SFIDFMT File Format Character
Value: 'F' Fixed format binary file.
'V' Variable format binary file.
'U' Unstructured binary file.
'T' Text
Virtual File format. Used to calculate the restart
position. (Section 1.5.3)
SFIDLRECL Maximum Record Size Numeric(5)
Maximum: 99999
Length in octets of the longest logical record which may be
transferred to a location. Only user data is included.
If SFIDFMT is 'T' or 'U' then this attribute must be set to
'00000'.
SFIDFSIZ File Size Numeric(7)
Maximum: 9999999
Space in 1K (1024 octet) blocks required at the Originator
location to store the Virtual File.
This parameter is intended to provide only a good estimate
of the Virtual File size.
SFIDREST Restart Position Numeric(9)
Maximum: 999999999
Virtual File restart position.
The count represents the:
- Record Number if SSIDFMT is 'F' or 'V'.
- File offset in 1K (1024 octet) blocks if SSIDFMT is
'U' or 'T'.
The count will express the transmitted user data (i.e.
before compression, header not included).
After negotiation between adjacent locations,
retransmission will start at the lowest value.
5.3.4 SFPA - Start File Positive Answer
o-------------------------------------------------------------------o
SFPA Start File Positive Answer
Start File Phase Speaker <---- Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 SFPACMD SFPA Command, '2' F X(1)
1 SFPAACNT Answer Count V 9(9)
o-------------------------------------------------------------------o
SFPACMD Command Code Character
Value: '2' SFPA Command identifier.
SFPAACNT Answer Count Numeric(9)
The Listener must enter a count lower or equal to the
restart count specified by the Speaker in the Start File
(SFID) command. The count expresses the received user
data. If restart facilities are not available, a count of
zero must be specified.
5.3.5 SFNA - Start File Negative Answer
o-------------------------------------------------------------------o
SFNA Start File Negative Answer
Start File Phase Speaker <---- Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 SFNACMD SFNA Command, '3' F X(1)
1 SFNAREAS Answer Reason F 9(2)
3 SFNARRTR Retry Indicator, (Y/N) F X(1)
o-------------------------------------------------------------------o
SFNACMD Command Code Character
Value: '3' SFNA Command identifier.
SFNAREAS Answer Reason Numeric(2)
Value: '01' Invalid filename.
'02' Invalid destination.
'03' Invalid origin.
'04' Storage record format not supported.
'05' Maximum record length not supported.
'06' File size is too big.
'10' Invalid record count.
'11' Invalid byte count.
'12' Access method failure.
'13' Duplicate file.
'99' Unspecified reason.
Reason why transmission can not proceed.
SFNARRTR Retry Indicator Character
Value: 'N' Transmission should not be retried.
'Y' The transmission may be retried latter.
This parameter is used to advise the Speaker if it should
retry at a latter point in time due to a temporary
condition at the Listener site, such as a lack of storage
space. It should be used in conjunction with the Answer
Reason code (SFNAREAS).
An invalid file name error code may be the consequence of a
problem in the mapping of the Virtual File on to a real
file. Such problems cannot always be resolved immediately.
It it therefore recommended that when a SFNA with Retry = Y
is received the User Monitor attempts to retransmit the
relevant file in a subsequent session.
5.3.6 DATA - Data Exchange Buffer
o-------------------------------------------------------------------o
DATA Data Exchange Buffer
Data Transfer Phase Speaker ----> Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 DATACMD DATA Command, 'D' F X(1)
1 DATABUF Data Exchange Buffer payload V X(n)
o-------------------------------------------------------------------o
DATACMD Command Code Character
Value: 'D' DATA Command identifier.
DATABUF Data Exchange Buffer payload String(n)
Variable length buffer containing the data payload. The
Data Exchange Buffer is described in Section 6.
5.3.7 CDT - Set Credit
o-------------------------------------------------------------------o
CDT Set Credit
Data Transfer Phase Speaker <---- Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 CDTCMD CDT Command, 'C' F X(1)
1 CDTRSV1 Reserved F X(2)
o-------------------------------------------------------------------o
CDTCMD Command Code Character
Value: 'C' CDT Command identifier.
CDTRSV1 Reserved String(2)
This field is reserved for future use.
5.3.8 EFID - End File
o-------------------------------------------------------------------o
EFID End File
End File Phase Speaker ----> Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 EFIDCMD EFID Command, 'T' F X(1)
1 EFIDRCNT Record Count V 9(9)
10 EFIDUCNT Unit Count V 9(12)
o-------------------------------------------------------------------o
EFIDCMD Command Code Character
Value: 'T' EFID Command identifier.
EFIDRCNT Record Count Numeric(9)
Maximum: 999999999
For SSIDFMT 'F' or 'V' the exact record count.
For SSIDFMT 'U' or 'T' zeros.
The count will express the real size of the file (before
compression, header not included). The total count is
always used, even during restart processing.
EFIDUCNT Unit Count Numeric(12)
Maximum: 999999999999
Exact number of units (octets) transmitted.
The count will express the real size of the file. The
total count is always used, even during restart processing.
5.3.9 EFPA - End File Positive Answer
o-------------------------------------------------------------------o
EFPA End File Positive Answer
End File Phase Speaker <---- Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 EFPACMD EFPA Command, '4' F X(1)
1 EFPACD Change Direction Indicator, (Y/N) F X(1)
o-------------------------------------------------------------------o
EFPACMD Command Code Character
Value: '4' EFPA Command identifier.
EFPACD Change Direction Indicator Character
Value: 'N' Change direction not requested.
'Y' Change direction requested.
This parameter allows the Listener to request a Change
Direction (CD) command from the Speaker.
5.3.10 EFNA - End File Negative Answer
o-------------------------------------------------------------------o
EFNA End File Negative Answer
End File Phase Speaker <---- Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 EFNACMD EFNA Command, '5' F X(1)
1 EFNAREAS Answer Reason F 9(2)
o-------------------------------------------------------------------o
EFNACMD Command Code Character
Value: '5' EFNA Command identifier.
EFNAREAS Answer Reason Numeric(2)
Value: '01' Invalid filename.
'02' Invalid destination.
'03' Invalid origin.
'04' Storage record format not supported.
'05' Maximum record length not supported.
'06' File size is too big.
'10' Invalid record count.
'11' Invalid byte count.
'12' Access method failure.
'13' Duplicate file.
'99' Unspecified reason.
Reason why transmission can not proceed.
5.3.11 ESID - End Session
o-------------------------------------------------------------------o
ESID End Session
End Session Phase Speaker ----> Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 ESIDCMD ESID Command, 'F' F X(1)
1 ESIDREAS Reason Code F 9(2)
3 ESIDCR Carriage Return F X(1)
o-------------------------------------------------------------------o
ESIDCMD Command Code Character
Value: 'F' ESID Command identifier.
ESIDREAS Reason Code Numeric(2)
Value '00' Normal session termination
'01' Command not recognised
An Exchange Buffer contains an invalid command code
(1st octet of the buffer).
'02' Protocol violation
An Exchange Buffer contains an invalid command for
the current state of the receiver.
'03' User code not known
A Start Session (SSID) command contains an unknown or
invalid Identification Code.
'04' Invalid password
A Start Session (SSID) command contained an invalid
password.
'05' Local site emergency close down
The local site has entered an emergency close down
mode. Communications are being forcibly terminated.
'06' Command contained invalid data
A field within a Command Exchange buffer contains
invalid data.
'07' Exchange Buffer size error
The length of the Exchange Buffer as determined by
the Stream Transmission Header is different to the
length implied by the Command Code.
'08' Resources not available
The request for connection has been denied due to a
resource shortage. The connection attempt should be
retried later.
'09' Time out
'10' Mode or capabilities incompatible
'99' Unspecified Abort code
An error was detected for which no specific code is
defined.
ESIDCR Carriage Return Character
Value: Character with hex value '0D' or '8D'.
5.3.12 CD - Change Direction
o-------------------------------------------------------------------o
CD Change Direction
Start File Phase Speaker ----> Listener
End File Phase Speaker ----> Listener
End Session Phase Initiator <---> Responder
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 CDCMD CD Command, 'R' F X(1)
o-------------------------------------------------------------------o
CDCMD Command Code Character
Value: 'R' CD Command identifier.
5.3.13 EERP - End to End Response
o-------------------------------------------------------------------o
EERP End to End Response
Start File Phase Speaker ----> Listener
End File Phase Speaker ----> Listener
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 EERPCMD EERP Command, 'E' F X(1)
1 EERPDSN Virtual File Dataset Name V X(26)
27 EERPRSV1 Reserved F X(9)
36 EERPDATE Virtual File Date stamp, (YYMMDD) V X(6)
42 EERPTIME Virtual File Time stamp, (HHMMSS) V X(6)
48 EERPUSER User Data V X(8)
56 EERPDEST Destination V X(25)
81 EERPORIG Originator V X(25)
o-------------------------------------------------------------------o
EERPCMD Command Code Character
Value: 'E' EERP Command identifier.
EERPDSN Virtual File Dataset Name String(26)
Dataset name of the Virtual File being transferred,
assigned by bilateral agreement.
No general structure is defined for this attribute.
See Virtual Files - Identification (Section 1.5.2)
EERPRSV1 Reserved String(9)
This field is reserved for future use.
EERPDATE Virtual File Date stamp String(6)
Format: 'YYMMDD' 6 decimal digits representing the year, month
and day respectively [ISO-8601].
Date stamp assigned by the Virtual File's Originator
indicating when the file was made available for
transmission.
See Virtual Files - Identification (Section 1.5.2)
EERPTIME Virtual File Time stamp String(6)
Format: 'HHMMSS' 6 decimal digits representing hours, minutes
and seconds respectively [ISO-8601].
Time stamp assigned by the Virtual File's Originator
indicating when the file was made available for
transmission.
See Virtual Files - Identification (Section 1.5.2)
EERPUSER User Data String(8)
May be used by the ODETTE-FTP in any way. If unused it
should be initialised to spaces. It is expected that a
bilateral agreement exists as to the meaning of the data.
EERPDEST Destination String(25)
Format: See Identification Code (Section 5.4)
Originator of the Virtual File.
This is the location that created (mapped) the data for
transmission.
EERPORIG Originator String(25)
Format: See Identification Code (Section 5.4)
Final Recipient of the Virtual File.
This is the location that will look into the Virtual File
content and perform mapping functions. It is also the
location that creates the EERP for the received file.
5.3.14 RTR - Ready To Receive
o-------------------------------------------------------------------o
RTR Ready To Receive
Start File Phase Initiator <---- Responder
End File Phase Initiator <---- Responder
-------------------------------------------------------------------
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 RTRCMD RTR Command, 'P' F X(1)
o-------------------------------------------------------------------o
RTRCMD Command Code Character
Value: 'P' RTR Command identifier.
5.4 Identification Code
The Initiator (sender) and Responder (receiver) participating in an
ODETTE-FTP session are uniquely identified by an Identification Code
based on [ISO 6523], Structure for the Identification of
Organisations (SIO). The locations are considered to be adjacent for
the duration of the transmission.
The SIO has the following format.
o-------------------------------------------------------------------o
Pos Field Description Format
-----+-----------+---------------------------------------+---------
0 SIOOID ODETTE Identifier F X(1)
1 SIOICD International Code Designator V 9(4)
5 SIOORG Organisation Code V X(14)
19 SIOCSA Computer Sub-Address V X(6)
o-------------------------------------------------------------------o
SIOOID ODETTE Identifier Character
Value: 'O' Indicates ODETTE assigned Organisation Identifier.
Other values may be used for non-ODETTE codes.
SIOICD International Code Designator String(4)
A code forming part of the Organisation Identifier.
SIOORG Organisation Code String(14)
A code forming part of the Organisation Identifier. This
field may contain the letters A to Z, the digits 0 to 9,
apace and hyphen characters.
SIOCSA Computer Sub-Address String(6)
A locally assigned address which uniquely identifies a
system within an organisation (defined by an Organisation
Identifier).
6. ODETTE-FTP Data Exchange Buffer
6.1 Overview
Virtual Files are transmitted by mapping the Virtual File records
into Data Exchange Buffers, the maximum length of which was
negotiated between the ODETTE-FTP entities via the Start Session
(SSID) commands exchanged during the Start Session Phase of the
protocol. The format is based on the Network Independent File
Transfer Protocol [NIFTP].
Virtual File records may be of arbitrary length. A simple
compression scheme is defined for strings of repeated characters.
An example of the use of the Data Exchange Buffer can be found in
Appendix A.
6.2 Data Exchange Buffer Format
For transmission of Virtual File records, data is divided into
Subrecords, each of which is preceded by a one octet Subrecord
Header.
The Data Exchange Buffer is made up of the initial Command character,
o--------------------------------------------------------
C H H H /
M D SUBRECORD D SUBRECORD D SUBRECORD /_
D R R R /
o-------------------------------------------------------
CMD
The Data Exchange Buffer Command Character, 'D'.
HDR
A one octet Subrecord Header defined as follows:
0 1 2 3 4 5 6 7
o-------------------------------o
E C
o F C O U N T
R
o-------------------------------o
Bits
0 End of Record Flag
Set to indicate that the next subrecord is the last
subrecord of the current record.
Unstructured files are transmitted as a single record, in
this case the flag acts as an end of file marker.
1 Compression Flag
Set to indicate that the next subrecord is compressed.
2-7 Subrecord Count
The number of octets in the Virtual File represented by the
next subrecord expressed as a binary value.
For uncompressed data this is simply the length of the
subrecord.
For compressed data this is the number of times that the
single octet in the following subrecord must be inserted in
the Virtual File.
As six bits are available, the next subrecord may
represent between 0 and 63 octets of the Virtual File.
6.3 Buffer Filling Rules
An Exchange Buffer may be any length up to the value negotiated in
the Start Session exchange.
Virtual File records may be concatenated within one Exchange Buffer
or split across a number of buffers.
A subrecord is never split between two Exchange Buffers. If the
remaining space in the current Exchange Buffer is insufficient to
contain the next 'complete' subrecord one of the following strategies
should be used:
1. Truncate the Exchange Buffer, and put the complete
subrecord (preceded by its header octet) in a new Exchange Buffer.
2. Split the subrecord into two, filling the remainder of the
Exchange Buffer with the first new subrecord and starting a new
Exchange Buffer with the second.
A record of length zero may appear anywhere in the Exchange Buffer.
A subrecord of length zero may appear anywhere in the record and/or
the Exchange Buffer.
7. Stream Transmission Buffer (TCP only)
7.1 Introduction
The ODETTE-FTP was originally designed to utilise the ISO Network
Service, specifically the X.25 specification. It relies on the fact
that the network service will preserve the sequence and boundaries of
data units transmitted through the network and that the network
service will pass the length of the data unit to the receiving
ODETTE-FTP. The TCP offers a stream based connection which does not
provide these functions.
In order to utilise the TCP stream without disruption to the existing
ODETTE-FTP a Stream Transmission Buffer (STB) is created by adding a
Stream Transmission Header (STH) to the start of all Command and Data
Exchange Buffers before they are passed to the TCP transport service.
This allows the receiving ODETTE-FTP to recover the original Exchange
Buffers.
STH - Stream Transmission Header
OEB - ODETTE-FTP Exchange Buffer
The Stream Transmission Buffer comprises of a STH and OEB.
o-----+-----------------+-----+--------------------+-----+------
STH OEB STH OEB STH OEB/
o-----+-----------------+-----+--------------------+-----+----
7.2 Stream Transmission Header Format
The Stream Transmission Header is shown below. The fields are
transmitted from left to right.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version Flags Length
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version
Value: 0001 (binary)
Stream Transmission Header version number.
Flags
Value: 0000 (binary)
Reserved for future use.
Length
Range: 5 - 100003 (decimal)
The length of the Stream Transmission Buffer (STH+OEB).
The smallest STB is 5 octets consisting of a 4 octet header
followed by a 1 octet Exchange Buffer such as a Change Direction
(CD) command.
The maximum Exchange Buffer length that can be negotiated is 99999
octets (Section 5.3.2) giving a STB length of 100003.
The length is expressed as a binary number with the most
significant bit on the left.
It is expected that implementations of this protocol will follow the
Internet robustness principle of being conservative in what is sent
and liberal in what is accepted.
8. Protocol State Machine
8.1 ODETTE-FTP State Machine
The operation of an ODETTE-FTP entity is formally defined by the
State Machine presented below. There are five State and Transition
tables and for each table additional information is given in the
associated Predicate and Action lists.
The response of an ODETTE-FTP entity to the receipt of an event is
defined by a Transition table entry indexed by the Event/State
intersection within the appropriate State table.
Each Transition table entry defines the actions taken, events
generated and new state entered. Predicates may be used within a
table entry to select the correct response on the basis of local
information held by the entity.
A transition table contains the following fields:
Index(I) State transition index.
Predicate A list of predicates used to select between different
possible transitions. The predicates are defined in the
Predicate and Action list.
Actions A list of actions taken by the entity. The actions are
defined in the Predicate and Action list.
Events Output events generated by the entity
Next State The new state of the entity.
8.2 Error Handling
The receipt of an event in a given state may be invalid for three
reasons.
1. The case is impossible by construction of the state automata,
denoted 'X' in the State tables. For example a timer which has
not been set cannot run out.
2. The event is the result of an error in the Network Service
implementation, also denoted 'X' in the state tables. The
Network Service implementation is considered to be correct.
3. For all other cases the event is considered to be a User Error,
denoted "U" in the state tables.
The State tables define the conditions under which a User event is
valid, thus preventing the generation of a protocol error by the
ODETTE-FTP entity as a result of a User Monitor error. The reaction
of the entity to such errors is undefined and regarded as a local
implementation issue.
The State tables also allow protocol errors due to the receipt of
invalid Exchange Buffers, to be detected. In such cases the reaction
of the entity to the error is defined.
8.3 States
The Command Mode is strictly a Half Duplex Flip-Flop Mode.
A_NC_ONLY Responder, Network Connection opened
The Responder has sent it's Ready Message (SSRM) and is
waiting for Start Session (SSID) from the Initiator.
A_WF_CONRS Responder Waiting for F_CONNECT_RS
The Responder has received the Initiator's Start Session
(SSID) and is waiting for a response (F_CONNECT_RS) from
it's User Monitor.
CDSTWFCD CD_RQ stored in WF_CD state
Since the User Monitor doesn't see the WF_CD state it may
send a Change Direction request (F_CD_RQ) before the
ODETTE-FTP receives a Change Direction (CD) command.
CLIP Close Input Pending
The Listener has received an End File (EFID) command and
is waiting for the Close File response (F_CLOSE_FILE_RS)
from it's User Monitor.
CLOP Close Out Pending
The Speaker has sent an End File (EFID) command and is
waiting for an End File Answer (EFPA or EFNA).
ERSTWFCD End to End Response stored in WF_CD state
Since the User Monitor doesn't see the WF_CD state it may
send F_EERP_RQ, before the ODETTE-FTP receives a Change
Direction (CD) command.
IDLE Connection IDLE
IDLELI Idle Listener
IDLELICD Idle Listener, F_CD_RQ Received
The ODETTE-FTP entity has become the Listener after
receiving a Change Direction request (F_CD_RQ) from the
User Monitor. The receipt of an End Session (ESID) is
valid in this state.
IDLESP Idle Speaker
IDLESPCD Idle Speaker, F_CD_IND Sent
The ODETTE-FTP entity has sent a Change Direction
indication (F_CD_IND) to the User Monitor. A Change
Direction request (F_CD_RQ) is invalid in this state.
I_WF_NC Initiator Waiting for Network Connection
The Initiator has requested a new network connection and
is waiting for a Connection confirmation (N_CON_CF) from
the Network Service.
I_WF_RM Initiator Waiting for Ready Message
Before sending Start Session (SSID), the Initiator must
wait for a Ready Message (SSRM) from the Responder.
I_WF_SSID Initiator Waiting for SSID
The Initiator has sent a Start Session (SSID) command and
is waiting for Start Session from the Responder.
OPI Open Input (Data Transfer Phase)
The Listener is waiting for the Speaker to send a Data
Exchange buffer.
OPIP Open Input Pending
The Listener has received a Start File (SFID) command and
is waiting for the Start File response (F_START_FILE_RS)
from it's User Monitor.
OPO Open Out (Data Transfer Phase)
The Speaker has received a Start File Positive Answer
(SFPA) and is waiting for a Data (F_DATA_RQ) or Close
File (F_CLOSE_FILE) request from it's User Monitor.
OPOP Open Out Pending
The Speaker has sent a Start File (SFID) command and is
waiting for a Start File Answer (SFPA or SFNA).
OPOWFC Open Out Wait for Credit
The Speaker is waiting for a Set Credit (CDT) command
before sending further Data Exchange buffers.
SFSTWFCD Start File Request stored in WF_CD state.
Since the User Monitor doesn't see the WF_CD state it may
send a Start File request (F_START_FILE_RQ) before the
ODETTE-FTP receives a Change Direction (CD) command.
WF_CD Wait for Change Direction
The Listener wishes to become the Speaker and is waiting
for a Change Direction (CD) command after sending an End
File Positive Answer (EFPA) requesting change direction.
WF_RTR Wait for Ready To Receive
The Initiator has sent an End to End Response (EERP)
command and must wait for Ready To Receive (RTR) from the
Responder.
WF_NDISC Wait for N_DISC_IND
ODETTE-FTP has sent an End Session (ESID) command and is
waiting for a Disconnection indication (N_DISC_IND) from
the Network Service.
8.4 Input Events
User Monitor Input Events (Section 3)
F_DATA_RQ F_CONNECT_RQ F_START_FILE_RQ F_CLOSE_FILE_RQ
F_EERP_RQ F_CONNECT_RS F_START_FILE_RS(+) F_CLOSE_FILE_RS(+)
F_CD_RQ F_ABORT_RQ F_START_FILE_RS(-) F_CLOSE_FILE_RS(-)
F_RELEASE_RQ
Network Input Events (Section 2.2)
N_CON_IND N_CON_CF N_DATA_IND N_DISC_IND N_RST_IND
Peer ODETTE-FTP Input Events (Section 4)
SSID SFID SFPA SFNA EFID EFPA EFNA
DATA ESID EERP RTR CD CDT SSRM
Internal Input Events
TIME-OUT - Internal ODETTE-FTP timer expires.
Input event parameters are denoted I.Event-name.Parameter-name within
the state table action and predicate lists. Their value can be
examined but not changed by the ODETTE-FTP entity.
8.5 Output Events
User Monitor Output Events (Section 3)
F_DATA_IND F_CONNECT_IND F_START_FILE_IND F_CLOSE_FILE_IND
F_EERP_IND F_CONNECT_CF F_START_FILE_CF(+) F_CLOSE_FILE_CF(+)
F_CD_IND F_ABORT_IND F_START_FILE_CF(-) F_CLOSE_FILE_CF(-)
F_RELEASE_IND
Network Output Events (Section 2.2)
N_CON_RQ N_CON_RS N_DATA_RQ N_DISC_RQ
Peer ODETTE-FTP Output Events (Section 4)
SSID SFID SFPA SFNA EFID EFPA EFNA
DATA ESID EERP RTR CD CDT SSRM
Output event parameters are denoted O.Event-name.Parameter-name
within the state table action and predicate lists. Their values can
be examined and changed by the ODETTE-FTP entity.
8.6 Local Variables
The following variables are maintained by the ODETTE-FTP entity to
assist the operation of the protocol. They are denoted V.Variable-
name within the state table action and predicate lists. Their value
can be examined and changed by the ODETTE-FTP entity. The initial
value of each variable is undefined.
Variable Type Comments
---------------------------------------------------------------------
Buf-size Integer Negotiated Exchange Buffer size.
Called-addr Address Used to build O.F_CONNECT_IND.Called-addr
Calling-addr Address To build O.F_CONNECT_IND.Calling-addr
Compression Yes/No Compression in used as agreed.
Credit_L Integer Listeners credit counter.
Credit_S Integer Speaker's credit counter.
Id String Used to build O.SSID.Id
Mode Sender-only, Receiver-only, Both.
Pswd String Password, used to build O.SSID.Pswd
Req-buf Primitive Input event (F_XXX_RQ) stored in WF_CD state.
Restart Yes/No Restart in used as agreed.
Restart-pos Integer Used only during file opening.
Window Integer The Credit value negotiated for the session.
---------------------------------------------------------------------
8.7 Local Constants
The following constants define the capabilities of a given ODETTE-FTP
entity. They are denoted C.Constant-name within the state table
action and predicate lists. Their value can be examined but not
changed by the ODETTE-FTP entity.
Constant Value Comments
---------------------------------------------------------------------
Cap-compression Yes/No Compression supported?
Cap-init Initiator Must be Initiator.
Responder Must be Responder.
Both Can be Initiator or Responder.
Cap-mode Sender-only Must be sender.
Receiver-only Must be receiver.
Both Can be sender or receiver.
Max-buf-size 127 < Int < 100000 Maximum buffer size supported.
Max-window Int < 1000 Local maximum credit value.
---------------------------------------------------------------------
8.8 Session Connection State Table
8.8.1 State Table
o----------------------------------------------o
Other States
--------------------------------------o
S A_WF_CONRS
----------------------------------o
T A_NC_ONLY
------------------------------o
A I_WF_SSID
--------------------------o
T I_WF_RM
----------------------o
E I_WF_NC
------------------o
IDLE
==================o---+---+---+---+---+---+---
F_CONNECT_RQ A X X X X X X
--------------+---+---+---+---+---+---+---
E N_CON_CF X C X X X X X
--------------+---+---+---+---+---+---+---
V SSRM X X H X X X X
--------------+---+---+---+---+---+---+---
E SSID X X X D E F F
--------------+---+---+---+---+---+---+---
N N_CON_IND B X X X X X X
--------------+---+---+---+---+---+---+---
T F_CONNECT_RS X U U U U G U
--------------+---+---+---+---+---+---+---
ESID(R=10) X X X F X X X
o----------------------------------------------o
8.8.2 Transition Table
I Predicate Actions Output Events Next State
===o=================================================================
A P1: F_ABORT_IND IDLE
not P1: 1 N_CON_RQ I_WF_NC
---+-----------------------------------------------------------------
B P3: N_DISC_RQ IDLE
not P3: N_CON_RS
SSRM A_NC_ONLY
---+-----------------------------------------------------------------
C 2 I_WF_RM
---+-----------------------------------------------------------------
D P2: 4,2,5 F_CONNECT_CF IDLESP
not P2: 4,2 ESID(R=10)
F_ABORT_IND(R,AO=L) WF_NDISC
---+-----------------------------------------------------------------
E P4: 4 N_DISC_RQ IDLE
not P4: F_CONNECT_IND A_WF_CONRS
---+-----------------------------------------------------------------
F F_ABORT_IND
N_DISC_RQ IDLE
---+-----------------------------------------------------------------
G P2: 4,2,5 SSID IDLELI
not P2: 4,2 ESID(R=10)
F_ABORT_IND(R,AO=L) WF_NDISC
---+-----------------------------------------------------------------
H 4,2,3 SSID I_WF_SSID
---------------------------------------------------------------------
8.8.3 Predicates and Actions.
Predicate P1: (No resources available) OR
(C.Cap-init = Responder) OR
(C.Cap-mode = Sender-only AND
I.F_CONNECT_RQ.Mode = Receiver-only) OR
(C.Cap-mode = Receiver-only AND
I.F_CONNECT_RQ.Mode = Sender-only)
Predicate P2: Negotiation of (Buf-size, Restart, Compression,
Mode, Credit) is OK.
Predicate P3: C.Cap-init = Initiator
Predicate P4: Mode in SSID incompatible with C.Cap-mode
Action 1: Set V.Mode from (C.Cap-mode, I.F_CONNECT_RQ.Mode)
Set V.Pswd, V.Id, V.Restart from I.F_CONNECT_RQ
Set V.Buf-size = C.Max-buf-size
Set V.Compression = C.Cap-compression
Build O.N_CON_RQ
Action 2: Start inactivity timer
Action 3: Set parameters in O.SSID = from local variables
Action 4: Stop timer
Action 5: Set V.Mode, V.Restart, V.Compression, V.Buf-size,
V.Window = from SSID
8.9 Error and Abort State Table
8.9.1 State Table
o--------------------------------------o
Other States
S ------------------------------o
T WF_NDISC
A --------------------------o
T I_WF_NC
E ----------------------o
IDLE
======================o---+---+---+---
TIME-OUT X X A B
------------------+---+---+---+---
E F_ABORT_RQ X A X C
V ------------------+---+---+---+---
E N_RST_IND X X A D
N ------------------+---+---+---+---
T N_DISC_IND X E F G
------------------+---+---+---+---
Invalid Buffer X X H I
o--------------------------------------o
8.9.2 Transition Table
I Predicate Actions Output Events Next State
===o=================================================================
A N_DISC_RQ IDLE
---+-----------------------------------------------------------------
B F_ABORT_IND
N_DISC_RQ IDLE
---+-----------------------------------------------------------------
C 1 N_DISC_RQ IDLE
---+-----------------------------------------------------------------
D 1 N_DISC_RQ
F_ABORT_IND IDLE
---+-----------------------------------------------------------------
E F_ABORT_IND IDLE
---+-----------------------------------------------------------------
F 1 IDLE
---+-----------------------------------------------------------------
G 1 F_ABORT_IND IDLE
---+-----------------------------------------------------------------
H WF_NDISC
---+-----------------------------------------------------------------
I 1,2 ESID(R=01)
F_ABORT_IND(R,AO=L) WF_NDISC
---------------------------------------------------------------------
8.9.3 Predicates and Actions.
Action 1: Stop inactivity timer
Action 2: Start inactivity timer
8.10 Speaker State Table 1
8.10.1 State Table
The following abbreviations are used in the Speaker State table.
F_REL_RQ(Ok) - F_RELEASE_RQ Reason = Normal
F_REL_RQ(Err) - F_RELEASE_RQ Reason = Error
o------------------------------------------------------------------o
Other State
----------------------------------------------------------o
WF_NDISC
------------------------------------------------------o
OPOWFC
--------------------------------------------------o
OPO
S ----------------------------------------------o
OPOP
T ------------------------------------------o
CDSTWFCD
A --------------------------------------o
SFSTWFCD
T ----------------------------------o
ERSTWFCD
E ------------------------------o
WF_CD
--------------------------o
WF_RTR
----------------------o
IDLESPCD
------------------o
IDLESP
===+==============o---+---+---+---+---+---+---+---+---+---+---+---
F_EERP_RQ A A W F W U U U U U U U
--------------+---+---+---+---+---+---+---+---+---+---+---+---
F_START_ B B W G W U U U U U X U
FILE_RQ
--------------+---+---+---+---+---+---+---+---+---+---+---+---
SFPA C C C C C C C K C C S C
--------------+---+---+---+---+---+---+---+---+---+---+---+---
E SFNA C C C C C C C L C C S C
--------------+---+---+---+---+---+---+---+---+---+---+---+---
V CD C C C H R I J C C C S C
--------------+---+---+---+---+---+---+---+---+---+---+---+---
E F_DATA_RQ U U U U U U U U M V S U
--------------+---+---+---+---+---+---+---+---+---+---+---+---
N CDT C C C C C C C C P O S C
--------------+---+---+---+---+---+---+---+---+---+---+---+---
T F_CD_RQ D U W T W U U U U U X U
--------------+---+---+---+---+---+---+---+---+---+---+---+---
F_REL_RQ(Ok) U E U U U U U U U U X U
--------------+---+---+---+---+---+---+---+---+---+---+---+---
F_REL_RQ(Err) Q Q Q Q Q Q Q Q Q Q S Q
--------------+---+---+---+---+---+---+---+---+---+---+---+---
RTR C C N C C C C C C C S C
o------------------------------------------------------------------o
8.10.2 Transition Table
I Predicate Actions Output Events Next State
===o=================================================================
A 1,2,3 EERP WF_RTR
---+-----------------------------------------------------------------
B P1: UE
not P1: 1,2,5 SFID OPOP
---+-----------------------------------------------------------------
C 1,2 ESID(R=02)
F_ABORT_IND(R,AO=L) WF_NDISC
---+-----------------------------------------------------------------
D 1,2 CD IDLELICD
---+-----------------------------------------------------------------
E 1,2 ESID(R=00) WF_NDISC
---+-----------------------------------------------------------------
F 4 ERSTWFCD
---+-----------------------------------------------------------------
G P1: UE
not P1: 6 SFSTWFCD
---+-----------------------------------------------------------------
H 1,2 IDLESP
---+-----------------------------------------------------------------
I 1,2,10 SFID OPOP
---+-----------------------------------------------------------------
J 1,2 CD IDLELICD
---+-----------------------------------------------------------------
K P2: 1,2 ESID(R=02)
F_ABORT_IND(R,AO=L) WF_NDISC
not P2: 1,2,7,12 F_START_FILE_CF(+) OPO
---+-----------------------------------------------------------------
L 1,2,8 F_START_FILE_CF(-) IDLESP
---+-----------------------------------------------------------------
M P3: 1,2,11,13 DATA OPOWFC
not P3: 1,2,11,13 DATA OPO
---+-----------------------------------------------------------------
N Note 3 IDLESP
---+-----------------------------------------------------------------
O 12 OPO
See Note 1
---+-----------------------------------------------------------------
P Protocol 1,2 ESID(R=02)
Error F_ABORT_IND(R,AO=L) WF_NDISC
---+-----------------------------------------------------------------
Q 1,2 ESID(R) WF_NDISC
---+-----------------------------------------------------------------
Continued -->
I Predicate Actions Output Events Next State
===o=================================================================
R 1,2,9 EERP WF_RTR
---+-----------------------------------------------------------------
S WF_NDISC
---+-----------------------------------------------------------------
T CDSTWFCD
---+-----------------------------------------------------------------
U User Error UE
---+-----------------------------------------------------------------
V User Error - Note 1 UE
---+-----------------------------------------------------------------
W User Error - Note 2 UE
---+-----------------------------------------------------------------
X Error
---------------------------------------------------------------------
8.10.3 Predicates and Actions.
Predicate P1: (I.F_START_FILE_RQ.Restart-pos > 0) AND
((V.Restart = No) OR (V.Mode = Receiver-only))
Note: Restart requested and not supported for this session.
Predicate P2: (I.SFPA.Restart-pos > V.Restart-pos)
Note: Protocol error due to the restart position in the
SFPA acknowledgement being greater than the position
requested in the SFID request.
Predicate P3: V.Credit_S - 1 = 0
Note: Speaker's Credit is exhausted.
Action 1: Stop inactivity timer
Action 2: Start inactivity timer
Action 3: Build an EERP from F_EERP_RQ
Action 4: Store F_EERP_RQ in V.Req-buf
Action 5: Build SFID from F_START_FILE_RQ
V.Restart-pos = I.F_START_FILE_RQ.Restart-pos
Action 6: Store F_START_FILE_RQ in V.Req-buf
Action 7: Build F_START_FILE_CF(+) from I.SFPA
Action 8: Build F_START_FILE_CF(-) from I.SFNA
Action 9: Build EERP from F_EERP_RQ stored in V.Req-buf
Action 10: Build SFID from F_START_FILE_RQ stored in V.Req-buf
Set V.Restart-pos
Action 11: Build Exchange Buffer
Action 12: V.Credit_S = V.Window
Action 13: V.Credit_S = V.Credit_S - 1
Note 1: The OPOWFC state prevents the Speaker from sending
data buffers because it is waiting for credit. The
ODETTE-FTP entity may need to control the flow of Data
requests (F_DATA_RQ) from it's User Monitor to protect
it's own buffers. Any such mechanism and the
behaviour of the entity should a User Error occur are
regarded as local implementation issues.
Note 2: The choice to accept this "Request/Event" while in
this state is a matter of local implementation. The
ODETTE state tables are based on the assumption that
this event cannot occur in this state and is
considered to be a user error (UE).
Note 3: It is a local matter to make the User Monitor aware
that since the RTR is received, the protocol machine
is now ready to accept the next request.
8.11 Speaker State Table 2
8.11.1 State Table
o---------------------------------o
S CLOP
T -------------------------o
A OPOWFC
T ---------------------o
E OPO
=====================o---+---+---
E F_CLOSE_FILE_RQ A E U
V -----------------+---+---+---
E EFPA B B C
N -----------------+---+---+---
T EFNA B B D
o---------------------------------o
8.11.2 Transition Table
I Predicate Actions Output Events Next State
===o=================================================================
A 1,2,5,7 EFID CLOP
---+-----------------------------------------------------------------
B 1,2 ESID(R=02)
F_ABORT_IND(R,AO=L) WF_NDISC
---+-----------------------------------------------------------------
C P1: 1,2,3 F_CLOSE_FILE_CF(+,SP=No)
CD IDLELI
not P1: 1,2,4 F_CLOSE_FILE_CF(+,SP=Yes) IDLESP
---+-----------------------------------------------------------------
D 1,2,6 F_CLOSE_FILE_CF(-) IDLESP
---+-----------------------------------------------------------------
E See Note 1
---+-----------------------------------------------------------------
U User Error UE
---------------------------------------------------------------------
8.11.3 Predicates and Actions.
Predicate P1: (I.EFPA.CD-Request = Yes) AND (V.Mode = Both)
Action 1: Stop inactivity timer
Action 2: Start inactivity timer
Action 3: O.F_CLOSE_FILE_CF(+).Speaker = No
Action 4: O.F_CLOSE_FILE_CF(+).Speaker = Yes
Action 5: Build EFID from F_CLOSE_FILE_RQ
Action 6: Build F_CLOSE_FILE_CF(-) from EFNA
Action 7: Set V.Credit_S = 0
Note 1: In order to respect the "half duplex" property of
ODETTE-FTP it is forbidden to send EFID while in the
OPOWFC state. EFID can be sent only in the OPO state.
The ODETTE-FTP implementation must avoid sending EFID
(or receiving F_CLOSE_FILE_RQ) while in the OPOWFC
state.
8.12 Listener State Table
8.12.1 State Table
o-----------------------------------------o
CLIP
---------------------------------o
OPI
S -----------------------------o
T OPIP
A -------------------------o
T IDLELICD
E ---------------------o
IDLELI
=====================o---+---+---+---+---
SFID A A B B B
-----------------+---+---+---+---+---
E DATA B B B I B
V -----------------+---+---+---+---+---
E EFID B B B J B
N -----------------+---+---+---+---+---
T F_START_FILE_RS U U H U U
-----------------+---+---+---+---+---
F_CLOSE_FILE_RS U U U U K
-----------------+---+---+---+---+---
CD C B B B B
-----------------+---+---+---+---+---
ESID R=Normal D F D D D
-----------------+---+---+---+---+---
ESID R=Error D D D D D
-----------------+---+---+---+---+---
EERP E G B B B
o-----------------------------------------o
8.12.2 Transition Table
I Predicate Actions Output Events Next State
===o=================================================================
A P1: 1,2 ESID(R=02)
F_ABORT_IND(R,AO=L) WF_NDISC
not P1: 1,2,3 F_START_FILE_IND OPIP
---+-----------------------------------------------------------------
B 1,2 ESID(R=02)
F_ABORT_IND(R,AO=L) WF_NDISC
---+-----------------------------------------------------------------
C 1,2 F_CD_IND IDLESPCD
---+-----------------------------------------------------------------
D 1 F_ABORT_IND(Received
ESID Reason,AO=D)
N_DISC_RQ IDLE
---+-----------------------------------------------------------------
E 4 F_EERP_IND
8 See Note 2
RTR IDLELI
---+-----------------------------------------------------------------
F 1 F_RELEASE_IND
N_DISC_RQ IDLE
---+-----------------------------------------------------------------
G F_EERP_IND
8 See Note 2
RTR IDLELI
---+-----------------------------------------------------------------
H P4: User Error UE
P2,not P4: 1,2 SFPA OPI
not(P2,P4): 1,2 SFNA IDLELI
---+-----------------------------------------------------------------
I P5: 1,2 ESID(R=02)
F_ABORT_IND(R,A0=L) WF_NDISC
not(P5,P6): 1,2,5 F_DATA_IND OPI
not P5,P6: 1,2 F_DATA_IND
6,7 See Note 1
CDT OPI
---+-----------------------------------------------------------------
J 1,2 F_CLOSE_FILE_IND CLIP
---+-----------------------------------------------------------------
K P2,P3: 1,2 EFPA(CD-Req) WF_CD
P2,not P3: 1,2 EFPA(no CD) IDLELI
not P2: 1,2 EFNA IDLELI
---+-----------------------------------------------------------------
U User Error UE
---------------------------------------------------------------------
8.12.3 Predicates and Actions.
Predicate P1: (I.SFID.Restart-pos > 0) AND (V.Restart = No)
Note: Invalid Start File command
Predicate P2: Positive Response
Predicate P3: I.F_CLOSE_FILE_RS(+).Speaker = Yes
Predicate P4: I.F_START_FILE_RS(+).Restart-pos > V.Restart
Predicate P5: V.Credit_L - 1 < 0
Note: Protocol Error because the Speaker has exceeded it's
available transmission credit.
Predicate P6: V.Credit_L - 1 = 0
Note: The Speaker's credit must be reset before it can send
further Data Exchange buffers.
Action 1: Stop inactivity timer.
Action 2: Start inactivity timer
Action 3: Build F_START_FILE_IND from I.SFID
V.Restart-pos = I.SFID.Restart-pos
Action 4: Build F_EERP_IND from I.EERP
Action 5: V.Credit_L = V.Credit_L - 1
Action 6: Wait for sufficient resources to receive up to
V.Window Data Exchange Buffers.
Action 7: V.Credit_L = V.Window
Action 8: Wait for resources required to process a new EERP.
Note 1: Flow control in case of reception.
The ODETTE-FTP Listener must periodically send new
credit to the Speaker. The timing of this operation
will depend on:
1. The User Monitor's capacity the receive data.
2. The number of buffers available to ODETTE-FTP.
3. The Speaker's available credit, which must be
equal to zero.
Note 2: Generally, the ODETTE-FTP Listener will send RTR
immediately after receiving EERP. If required, it can
delay the RTR until the resources required to process
a new EERP are available.
8.13 Example
Consider an ODETTE-FTP entity that has sent a Start File (SFID)
command and entered the Open Out Pending (OPOP) state. It's response
on receiving a Positive Answer (SFPA) is documented in Speaker State
Table 1 which shows that transition 'K' should be applied and is
interpreted as follows:
if (I.SFPA.Restart-pos > V.Restart-pos) then
begin // invalid restart
Actions: Stop inactivity timer, // reset timer
Start inactivity timer;
Output: ESID(R=02), // to peer ODETTE-FTP
F_ABORT_IND(R,AO=L); // to user monitor
New State: WF_NDISC;
end
else begin
Actions: Stop inactivity timer, // reset timer
Start inactivity timer;
Build F_START_FILE_CF(+) from I.SFPA
V.Credit_S = V.Window // initialise credit
Output: F_START_FILE_CF(+); // to user monitor
New State: OPO;
end
The ODETTE-FTP checks the restart position in the received Start File
Positive Answer (SFPA) command. If it is invalid it aborts the
session by sending an End Session (ESID) command to it's peer and an
Abort indication (F_ABORT_IND) to it's User Monitor. If the restart
position is valid a Start File confirmation (F_START_FILE_CF) is
built and sent to the User Monitor, the credit window is initialised
and the Open Out (OPO) state is entered.
9. Security Considerations
ODETTE-FTP exchanges user identity and password information in clear
text. It is therefore recommended that a lower layer (session,
network or linkage) security protocol is used to protect the session
from casual identity collection.
Appendix A. Virtual File Mapping Example
This example demonstrates the mapping of a Virtual File into a
sequence of ODETTE-FTP Data Exchange Buffers and shows how each
Stream Transmission Buffer is built from an ODETTE-FTP Data Exchange
Buffer prefixed by a Stream Transmission Header.
Each line in this extract from 'The Hunting of the Snark' by Lewis
Carroll [SNARK] is considered to be a separate record in a file
containing variable length records. Note that it does not represent
a text file and CR/LF record separators are not used. The blank line
is represented by a zero length record.
"It's a Snark!" was the sound that first came to their ears,
And seemed almost too good to be true.
Then followed a torrent of laughter and cheers:
Then the ominous words "It's a Boo-"
Then, silence. Some fancied they heard in the air
A weary and wandering sigh
Then sounded like "-jum!" but the others declare
It was only a breeze that went by.
Assuming that the minimum exchange buffer length of 128 octets has
been negotiated the result of mapping the text into Stream
Transmission Buffers may be as follows.
Stream Transmission Buffer 1
Text : ....D."It' s a Snark! " was the sound that first cam
Hex-H : 10084B2472 7262566762 2276727662 7676627667 2667772666
Hex-L : 00044C2947 30103E12B1 2071304850 3F5E404814 069234031D
Key : ----D!.... .......... .......... .......... ..........
Text : e to their ears,. .A nd seemed almost too good to b
Hex-H : 6276276667 26677242A4 6627666662 6666772766 2666627626
Hex-L : 504F048592 05123C5061 E40355D540 1CDF3404FF 07FF404F02
Key : .......... ......!.!. .......... .......... ..........
Text : e true..Th en followe d a torren t
Hex-H : 6277762156 6626666676 6262767766 72
Hex-L : 504255E848 5E06FCCF75 40104F225E 40
Key : .......!.. .......... .......... ..
Text : ....D.of l aughter an d cheers:. .Then the ominous w
Hex-H : 1007496626 6766767266 6266667734 2A56662766 2666667727
Hex-L : 000847F60C 157845201E 40385523A5 04485E0485 0FD9EF5307
Key : ----D!.... .......... .........! .!........ ..........
Text : ords "It's a Boo-".. Then, sile nce. Some fancied t
Hex-H : 6767224727 262466228B 5666227666 6662225666 2666666627
Hex-L : F243029473 0102FFD202 485EC039C5 E35E003FD5 061E395404
Key : .......... ........!! .......... .......... ..........
Text : hey heard in the air
Hex-H : 6672666762 6627662667
Hex-L : 8590851240 9E04850192
Key : .......... ..........
Stream Transmission Buffer 3
Text : ....D. .A weary and wandering sigh.Then sounded li
Hex-H : 1007442942 7667726662 7666676662 7666B56662 7676666266
Hex-L : 0008450A10 7512901E40 71E4529E70 39780485E0 3F5E4540C9
Key : ----D!.!.. .......... .......... ....!..... ..........
Text : ke "-jum!" but the o thers decl are. .It w as only a
Hex-H : 6622267622 2677276626 7667726666 67642A4727 6726667262
Hex-L : B502DA5D12 025404850F 485230453C 1255029407 130FEC9010
Key : .......... .......... .......... ...!.!.... ..........
Text : breeze tha t went by.
Hex-H : 6766762766 7276672672
Hex-L : 2255A50481 4075E4029E
Key : .......... ..........
Notes:
Hex-H High order bits of octet
Hex-L Low order bits of octet
Key: ---- Stream Transmission Header
D Data Exchange Buffer command code 'D'
! Subrecord header octet
. Place holder
All headers are represented with a period in the Text line.
Each Data Exchange Buffer is preceded by a Stream Transmission
Header.
In the above mapping the first Data Exchange Buffer is 128 octets in
length. The last record has been continued in the second buffer.
The second Data Exchange Buffer has been truncated at 116 octets to
finish at the end of a record. The following record being completely
contained in the third buffer. This is an alternative to spanning
the record as shown between the first and second Data Exchange
Buffers.
The blank line has been encoded as a single header octet of '80' hex,
indicating a zero length subrecord with the end of record flag set.
The indented lines have been compressed.
Appendix B. ISO 646 Character Subset
o-----------------------------------------------------------------o
7 0 0 0 0 1 1 1 1
B -+-----+-----+-----+-----+-----+-----+-----+-----
I 6 0 0 1 1 0 0 1 1
T -+-----+-----+-----+-----+-----+-----+-----+-----
5 0 1 0 1 0 1 0 1
----+-----+-----+-----+-----+-----+-----+-----+-----
------------ 0 1 2 3 4 5 6 7
BIT
4 3 2 1
============o====o=====+=====+=====+=====+=====+=====+=====+=====
0 0 0 0 0 SP 0 P
---------------------+-----+-----+-----+-----+-----+-----+-----
0 0 0 1 1 1 A Q
------------+---------+-----+-----+-----+-----+-----+-----+-----
0 0 1 0 2 2 B R
------------+---------+-----+-----+-----+-----+-----+-----+-----
0 0 1 1 3 3 C S
------------+---------+-----+-----+-----+-----+-----+-----+-----
0 1 0 0 4 4 D T
------------+---------+-----+-----+-----+-----+-----+-----+-----
0 1 0 1 5 5 E U
------------+---------+-----+-----+-----+-----+-----+-----+-----
0 1 1 0 6 & 6 F V
------------+---------+-----+-----+-----+-----+-----+-----+-----
0 1 1 1 7 7 G W
------------+---------+-----+-----+-----+-----+-----+-----+-----
1 0 0 0 8 ( 8 H X
------------+---------+-----+-----+-----+-----+-----+-----+-----
1 0 0 1 9 ) 9 I Y
------------+---------+-----+-----+-----+-----+-----+-----+-----
1 0 1 0 10 J Z
------------+---------+-----+-----+-----+-----+-----+-----+-----
1 0 1 1 11 K
------------+---------+-----+-----+-----+-----+-----+-----+-----
1 1 0 0 12 L
------------+---------+-----+-----+-----+-----+-----+-----+-----
1 1 0 1 13 - M
------------+---------+-----+-----+-----+-----+-----+-----+-----
1 1 1 0 14 . N
------------+---------+-----+-----+-----+-----+-----+-----+-----
1 1 1 1 15 / O
o-----------------------------------------------------------------o
Acknowledgements
This document draws extensively on revision 1.3 of the ODETTE File
Transfer Specification [OFTP].
Numerous people have contributed to the development of this protocol
and their work is hereby acknowledged. The extensions required to
utilise the Transmission Control Protocol were formulated and agreed
by the current members of ODETTE Working Group Four, who also
provided helpful reviews and comments on this document.
References
[OFTP] Organisation for Data Exchange by Tele Transmission in
Europe, Odette File Transfer Protocol, Revision 1.3:1993
[RFC-739] Postel, J., Transmission Control Protocol, STD 7, RFC739,
September 1981
[ISO-646] International Organisation for Standardisation, ISO
Standard 646:1991, "Information technology -- ISO 7-bit coded
character set for information interchange", 1991
[ISO-6523] International Organisation for Standardisation, ISO
Standard 6523:1984, "Data interchange -- Structures for the
identification of organisations", 1984
[ISO-8601] International Organisation for Standardisation, ISO
Standard 8601:1988 "Data elements and interchange formats --
Information interchange -- Representation of dates and times", 1988
[NIFTP] High Level Protocol Group, "A Network Independent File
Transfer Protocol", 1981
[SNARK] Carroll, Lewis "The Hunting of the Snark", 1876
ODETTE Address
The ODETTE File Transfer Protocol is a product of Working Group Four
of the Organisation for Data Exchange by Tele Transmission in Europe.
The working group can be contacted via the ODETTE Secretariat:
ODETTE Secretariat
Forbes House
Halkin Street
London
SW1X 7DS
United Kingdom
Phone: +44 (0)171 344 9227
Fax: +44 (0)171 235 7112
EMail odette@odette.org
keith.oxley@odette.org
stephanie.bioux@odette.org
Author's Address
The author can be contacted at
David Nash
Ford Motor Company Limited
Room 1/148, Central Office
Eagle Way
Warley
Brentwood
Essex
CM13 3BW
United Kingdom
Phone: +44 (0)1277 253043
EMail: dnash@ford.com
