





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





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   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



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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).




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   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.








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                              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.







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   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.






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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.




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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.








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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.






























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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




















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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.













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





















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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.





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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:



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      - 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



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      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.



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   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.




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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



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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





















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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)



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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(+))



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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.




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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.





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   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







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   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.





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      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











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   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








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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.



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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.




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      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'.











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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.




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   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.







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   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'.











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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)



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   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)






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   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



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   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.






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   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.












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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.






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             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



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   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).





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             '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.






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   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.






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   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.



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   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.



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





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   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.



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




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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.









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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.



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   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.




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   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.






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   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



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   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.













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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.
   ---------------------------------------------------------------------







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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


















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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






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       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













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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











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   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



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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 -->




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    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



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       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



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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.






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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


















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




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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.



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                  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.




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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!.... .......... .........! .!........ ..........



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      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.




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   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.















































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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




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RFC 2204             ODETTE File Transfer Protocol        September 1997


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, RFC 739,
   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
















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RFC 2204             ODETTE File Transfer Protocol        September 1997


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















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