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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

Nash Informational [Page 1] RFC 2204 ODETTE File Transfer Protocol September 1997

 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

Nash Informational [Page 2] RFC 2204 ODETTE File Transfer Protocol September 1997

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).

Nash Informational [Page 3] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 4] RFC 2204 ODETTE File Transfer Protocol September 1997

                            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.

Nash Informational [Page 5] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 6] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 7] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 8] RFC 2204 ODETTE File Transfer Protocol September 1997

2.2.4 Network Reset

  1. —–> 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.

Nash Informational [Page 9] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 10] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 11] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 12] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 13] RFC 2204 ODETTE File Transfer Protocol September 1997

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:

Nash Informational [Page 14] RFC 2204 ODETTE File Transfer Protocol September 1997

  1. The current Listener receives F_CLOSE_FILE_IND

(Speaker = choice).

  1. 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.
  1. 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:
  1. Only the Speaker may send an End to End Response request.
  1. Invoking the EERP service does not change the turn.
  1. 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

Nash Informational [Page 15] RFC 2204 ODETTE File Transfer Protocol September 1997

    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.

Nash Informational [Page 16] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 17] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 18] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 19] RFC 2204 ODETTE File Transfer Protocol September 1997

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)

Nash Informational [Page 20] RFC 2204 ODETTE File Transfer Protocol September 1997

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(+))

Nash Informational [Page 21] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 22] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 23] RFC 2204 ODETTE File Transfer Protocol September 1997

 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

Nash Informational [Page 24] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 25] RFC 2204 ODETTE File Transfer Protocol September 1997

    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

Nash Informational [Page 26] RFC 2204 ODETTE File Transfer Protocol September 1997

 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

Nash Informational [Page 27] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 28] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 29] RFC 2204 ODETTE File Transfer Protocol September 1997

    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'.

Nash Informational [Page 30] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 31] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 32] RFC 2204 ODETTE File Transfer Protocol September 1997

 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'.

Nash Informational [Page 33] RFC 2204 ODETTE File Transfer Protocol September 1997

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)

Nash Informational [Page 34] RFC 2204 ODETTE File Transfer Protocol September 1997

 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)

Nash Informational [Page 35] RFC 2204 ODETTE File Transfer Protocol September 1997

 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

Nash Informational [Page 36] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 37] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 38] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 39] RFC 2204 ODETTE File Transfer Protocol September 1997

           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

Nash Informational [Page 40] RFC 2204 ODETTE File Transfer Protocol September 1997

 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).

Nash Informational [Page 41] RFC 2204 ODETTE File Transfer Protocol September 1997

           '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.

Nash Informational [Page 42] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 43] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 44] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 45] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 46] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 47] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 48] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 49] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 50] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 51] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 52] RFC 2204 ODETTE File Transfer Protocol September 1997

 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

Nash Informational [Page 53] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 54] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 55] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 56] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 57] RFC 2204 ODETTE File Transfer Protocol September 1997

     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

Nash Informational [Page 58] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 59] RFC 2204 ODETTE File Transfer Protocol September 1997

 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

Nash Informational [Page 60] RFC 2204 ODETTE File Transfer Protocol September 1997

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 -->

Nash Informational [Page 61] RFC 2204 ODETTE File Transfer Protocol September 1997

  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

Nash Informational [Page 62] RFC 2204 ODETTE File Transfer Protocol September 1997

     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

Nash Informational [Page 63] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 64] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 65] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 66] RFC 2204 ODETTE File Transfer Protocol September 1997

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.

Nash Informational [Page 67] RFC 2204 ODETTE File Transfer Protocol September 1997

                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.

Nash Informational [Page 68] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 69] RFC 2204 ODETTE File Transfer Protocol September 1997

    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.

Nash Informational [Page 70] RFC 2204 ODETTE File Transfer Protocol September 1997

 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.

Nash Informational [Page 71] RFC 2204 ODETTE File Transfer Protocol September 1997

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

Nash Informational [Page 72] 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

Nash Informational [Page 73] 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

Nash Informational [Page 74]

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