Document: FTS-0008
Version:  003
Date:     15-Oct-1990
Updates:  FTS-0001



                  An Enhanced FidoNet(r) Technical Standard
                 Extending FTS-0001 to include Bark requests

                            October 15, 1990




Status of this document:

    This document specifies an optional standard for the FidoNet community.
    Implementation of the protocols defined in this document is not mandatory,
    but all implementations of these protocols are expected to adhere to this
    standard.  Distribution of this document is subject to the limitations of
    the copyright notice displayed below.


    Copyright 1989-90 by Philip L. Becker.  Portions of this document are
    copyright 1986-90 by Randy Bush and are incorporated with his consent.
    All rights reserved.  A right to distribute only without modification and
    only at no charge is granted.  Under no circumstances is this document to
    be reproduced or distributed as part of or packaged with any product or
    other sales transaction for which any fee is charged.  Any and all other
    reproduction or excerpting requires the explicit written consent of the
    copyright holders.


































 A. Introduction

 1. This Document

    This document describes the standard for "Bark" type FidoNet file
    request operation.  Bark file requests are an extension to the basic
    FTS-0001 mail session, and this document presents these requests as a
    modification to that document.

 2. What are File Requests?

    File Requests are a way of requesting that a specific file be sent during
    a FidoNet mail session.  This has many advantages over simply logging on to
    a BBS and downloading a file:

       o  You need not be a validated user

       o  You don't have to spend time searching for the file on the BBS

       o  You can schedule the file request to take place at any time without
          your being near your computer.

    There are two commonly used types of file requests on FidoNet today, WaZOO
    and Bark requests.  WaZOO requests are used by Opus and BinkleyTerm, and
    are not documented here.  See the document FTS-0006 by V. Perriello for a
    description of these.   Bark requests were the first file request extension
    to the FTS-0001 protocol, and are supported (at least partially) by many
    mailers, including SEAdog, Dutchie, BinkleyTerm, and to a certain extent
    Opus.  This document describes how to implement Bark-type file requests.


 B. Terms Used in this Document

 1. The diagrams and notations used in this document are the same as those used
    in the FTS-0001 document.  Please see FTS-0001 for a description of these.
    This document should be considered as an extension to the FTS-0001 session
    layer protocol, and you will require FTS-0001 in addition to this document
    to fully understand what is presented here.
  
    In addition to the data description language described in FTS-0001 section
    A.4, one extra terminal used in this notation:
  
    (* terminals *)
    someName<max> - String of up to max chars, NOT null terminated
 C. Performing File Requests

 1. Introduction

    A Bark request consists of transmitting a special Bark Request packet which
    contains a filename, a date (used for update requests), and optionally a
    password.  The system receiving the request then decides if it can send the
    requested file or not, and if it can does so using the same protocol used
    to send attached files.  Bark request handling is always controlled by the
    answering system, and consists of two phases.  In phase one, the receiving
    system asks the calling system to honor requests it may have to ask for
    files from the caller.  In phase two, the receiving system allows the
    calling system to request files from it.

    Update file requests are the same as normal file requests, with one
    exception.  If the date in the Bark Request packet (described below) is
    greater than or equal to the date of the actual file requested, the file
    will not be sent.  The requestor should set the date to the date of the
    the actual file on its own end if an update request is desired.


 D. The Bark Request Packet

 1. Data Link Layer Data Definition.
 
    The Bark Request packet is a variable-sized packet containing a header, a
    filename, a date (which is used only for update requests - in a normal file
    request it's 0) and an optional password. When receiving a Bark Request
    packet, the ETX may be used to determine the end of the data portion. Note
    that the CRC is sent in the reverse byte order of a normal CRC XMODEM data
    block (see FTS-0001 section G.1).

    Note: some systems will send a password in the data block even if none is
    needed.  Incoming passwords should be ignored unless the other system is
    trying to request a passworded file.

  

                          Bark File Request Packet
      Offset
      dec hex
              .-----------------------------------------------.
        0   0 |       ACK - Start of Bark Request - 06H       |
              +-----------------------------------------------+
        1   1 |     Filename - Packed DOS file format         |
              +-----------------------------------------------+
        n   n |              SPACE - 20H                      |
              +-----------------------------------------------+
        n   n |              Date (0 if not Update Request)   |
              +-----------------------------------------------+
        n   n |      SPACE - 20H  (only if pswd follows)      |
              +-----------------------------------------------+
        n   n |         Password (optional)                   |
              +-----------------------------------------------+
        n   n |       ETX -  End of RESYNC packet  - 03H      |
              +-----------------------------------------------+
        n   n |     (*1)     CRC  low order byte              |
              +-----------------------------------------------+
        n   n |     (*1)     CRC high order byte              |
              `-----------------------------------------------'

              *1 - CRC does not include the ACK or ETX and is
                   in the reverse byte order from the CRC in a
                   normal XMODEM data packet.
 2. Data Description Notation of Bark Request Packet

    DataBlock (no password) = ACK
                              Filename<12>
                              Space
                              Date<11>
                              ETX
                              CRC
  
    DataBlock (with password) = ACK
                                Filename<12>
                                Space
                                Date<11>
                                Space
                                Password<6|8>
                                ETX
                                CRC
  
    ACK   = 06H       (* Header for file request block *)
    Space = 20H       (* Space character *)
    ETX   = 03H       (* End of block *)
  
    Filename          (* Name of file requested *)
    Date              (* ASCII string; the number of seconds
                         since midnight, January 1, 1970 *)
    Password          (* The password needed to request this
                         file, if any.  Maximum length is 6 for
                         BinkleyTerm and Opus, 8 for SEAdog
                         and Dutchie. *)
  
    CRC = crc[2]      (* CCITT Cyclic Redundancy Check.  The
                         same algorithm as used for XModem
                         CRCs.  The CRC is calculated on
                         all data in the block between but
                         not including the ACK and the ETX *)
 E. Session Layer Protocol:

    This section describes the modified FTS-0001 session layer protocol.  This
    is the only area of FTS-0001 which is modified to implement Bark style file
    requests.  File Requests are performed at the end of the normal FidoNet
    mail session, after any mail pickup is performed.

    The diagrams below desribe the session level protocol with Bark file
    requests implemented.  The state tables have been broken into subroutines
    but the FTS-0001 portion is not functionally changed.  FTS-0001 sender
    states S4 through S7 are now table "Send Mail SM0".  FTS-0001 receiver
    states R3 through R6 are now table "Receive Mail RM0".  They are not
    functionally changed in any way from FTS-0001, they are just broken out
    to allow them to be used as subroutines.  Finally Sender states S0 through
    S3 are unchanged, as are Receiver states R0 through R2.

    The remaining FTS-0001 states are enhanced to implement the Bark file
    request protocol. In addition, the subroutine state tables "Send Bark SB0"
    and "Receive Bark RB0" have been added to handle the actual file requests.
 
    The following diagrams fully replace the Session Layer protocol state
    tables in FTS-0001.  No other changes to FTS-0001 are required to implement
    the Bark File request feature.
    Sender  (Top level)

    .-----+----------+-------------------------+-------------------------+-----.
    |State| State    | Predicate(s)            | Action(s)               | Next|
    |  #  | Name     |                         |                         | St  |
    +-----+----------+-------------------------+-------------------------+-----+
    | S0  | SendInit |                         | dial modem              | S1  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | S1  | WaitCxD  |1| carrier detected      | delay 1-5 seconds       | S2  |
    |     |  (*1)    | |                       | Set SLO if > 2400bps,   |     |
    |     |          | |                       | Reset SLO if <= 2400bps |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| busy, etc.            | report no connection    | exit|
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| voice                 | report no carrier       | exit|
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |4| carrier not detected  | report no connection    | exit|
    |     |          | | within 60 seconds     |                         |     |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | S2  | WhackCRs |1| over 30 seconds       | report no response <cr> | exit|
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| ?? <cr>s received     | delay 1 sec             | S3  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| <cr>s not received    | send <cr> <sp> <cr> <sp>| S2  |
    |     |          | |                       |   delay ??? secs        |     |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | S3  | WaitClear|1| no input for 0.5 secs | send TSYNCH = AEH       | S4  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| over 60 seconds       | hang up, report garbage | exit|
    |     |          | | and line not clear    |                         |     |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | S4  | SendMail |                         | (Send Mail SM0)         | S5  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | S5  | TryPickup|1| Rcv TSYNC             | (Receive Mail RM0)      | S5  |
    |     |   (*2)   +-+-----------------------+-------------------------+-----+
    |     |          |2| Rcv SYN               | (Receive Bark Req RB0)  | S5  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| Rcv ENQ               | (Do Bark Requests SB0)  | S5  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |4| Rcv 'C' or NAK        | Send EOT                | S5  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |5| Rcv Other Char        | Send SUB                | S5  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |6| No Data for 45 secs   | Hang Up                 | exit|
    `-----+----------+-+-----------------------+-------------------------+-----'

    *1 - This state is shown for the extended SEAlink protocol.  Omit the
         set/reset SLO actions if adding Bark to a strict FTS-0001 protocol
         implementation, or if not implementing overdrive in SEAdog.
   
    *2 - To refuse to pickup mail (S5.1) may send a CAN and stay in (S5).

    Note: Although the above shows the sender emitting only one TSYNCH, it is
    recommended that a timeout of 5-20 seconds should initiate another TSYNCH.
    The receiver should tolerate multiple TSYNCHs.
    Receiver (Top Level)

    The  receiving FSM is given  an external timer, the expiration of  which
    will cause termination with a result of 'no calls' (R0.2).
    .-----+----------+-------------------------+-------------------------+-----.
    |State| State    | Predicate(s)            | Action(s)               | Next|
    |  #  | Name     |                         |                         | St  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R0  | WaitCxD  |1| carrier detected      |                         | R1  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| external timer expires| report no calls         | exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R1  | WaitBaud |1| baud rate detected    | send signon with <cr>s  | R2  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| no detect in ?? secs  | hang up, report no baud | exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R2  | WaitTsync|1| TSYNCH received       | ignore input not TSYNCH | R3  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| 60 seconds timeout    | hang up, report not Fido| exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R3  | RecMail  |                         | (Receive Mail RM0)      | R4  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R4  | AllowPkup|1| Have pickup for sender| Send Tsync,             | R5  |
    |     |          | |                       |   Set T1=1 sec          |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| No pickup for sender  |                         | R6  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R5  | WtPickup |1| Rcv NAK or 'C'        | (Send Mail SM0)         | R6  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| Rcv SUB               | Send Tsync,             | R5  |
    |     |          | |                       |   Set T1=1 sec          |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| Rcv CAN               | Report Mail Refused     | R6  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |4| T1 expired            | Send Tsync,             | R5  |
    |     |          | |                       |   Set T1=1 sec          |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |5| 45 secs in R5         | Hang Up, report error   | exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R6  | AskBark  |1| Wish to make requests | Send SYN                | R7  |
    |     |   (*1)   +-+-----------------------+-------------------------+-----+
    |     |          |2| No requests to make   |                         | R8  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R7  | DoRequest|1| Rcv CAN               | Report Requests Refused | R8  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| Rcv ENQ               | (Send Bark SB0)         | R8  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| Rcv SUB               | Send SYN                | R7  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |4| Rcv NAK or 'C'        | Send EOT                | R6  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |5| Rcv Other             | eat character           | R7  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |6| 5 sec, no input       | Send SYN                | R7  |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |7| 45 secs in R7         |                         | R8  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | R8  | WtPickup |1| Allow File Request    | (Receive Bark RB0),     | exit|
    |     |          | |                       |   Hang Up               |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| Disallow Requests     | Hang Up                 | exit|
    `-----+----------+-+-----------------------+-------------------------+-----'
    *1 - Some implementations always do (R6.1) even if they have no requests.
    Sender - Send Mail

    .-----+----------+-------------------------+-------------------------+-----.
    |State| State    | Predicate(s)            | Action(s)               | Next|
    |  #  | Name     |                         |                         | St  |
    +-----+----------+-------------------------+-------------------------+-----+
    | SM0 | SendMail |                         | (XMODEM send packet XS0)| SM1 |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | SM1 | CheckMail|1| XMODEM successful     | (Fido registers success)| SM2 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| XMODEM fail or timeout| hang up, report mail bad| exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | SM2 | SendFiles|                         | (BATCH send files BS0)  | SM3 |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | SM3 | CheckFile|1| BATCH send successful | report success          | exit|
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| BATCH send failed     | hang up, rept files fail| exit|
    `-----+----------+-+-----------------------+-------------------------+-----'



    Sender - Send Bark

    .-----+----------+-------------------------+-------------------------+-----.
    |State| State    | Predicate(s)            | Action(s)               | Next|
    |  #  | Name     |                         |                         | St  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | SB0 | SendBark |1| File to request       | Build Bark Request Pkt, | SB1 |
    |     |          | |                       |   Set tries = 0         |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| No more files to req  | Send ETB                | exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | SB1 | AskFile  |                         | Send Bark Packet        | SB2 |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | SB2 | RcvFile  |1| Rcv ACK               | (Batch Receive BR0)     | SB3 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| Tries > 5             | Send ETB, report failed | exit|
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| Rcv Other             | Purge input, Incr tries | SB1 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |4| 10 sec w/o ACK        | Incr tries              | SB1 |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | SB3 | NxtFile  |1| Rcv ENQ               |                         | SB0 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| Rcv Other             | Purge Input             | SB3 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| 5 sec, no input       | Send SUB                | SB3 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |4| 45 sec in SB3         | Hang up, report error   | exit|
    `-----+----------+-+-----------------------+-------------------------+-----'
    Sender & Receiver - Receive Mail

    .-----+----------+-------------------------+-------------------------+-----.
    |State| State    | Predicate(s)            | Action(s)               | Next|
    |  #  | Name     |                         |                         | St  |
    +-----+----------+-------------------------+-------------------------+-----+
    | RM0 | RecMail  |                         | (XMODEM rec packet XR0) | RM1 |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | RM1 | XRecEnd  |1| XMODEM successful     | delay 1 second          | RM2 |
    |     |          | |                       |   flush input           |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| XMODEM failed         | hang up, rept mail fail | exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | RM2 | RecFiles |                         | (BATCH rec files BR0)   | RM3 |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | RM3 | ChkFiles |1| BATCH recv successful | delay 2 secs, rprt good | exit|
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| BATCH recv failed     | hang up, report bad file| exit|
    `-----+----------+-+-----------------------+-------------------------+-----'


    Sender & Receiver - Receive Bark

    .-----+----------+-------------------------+-------------------------+-----.
    |State| State    | Predicate(s)            | Action(s)               | Next|
    |  #  | Name     |                         |                         | St  |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | RB0 | HonorReq |1| Ok to honor request   | Purge Input, Send ENQ,  | RB1 |
    |     |          | |                       |   Set T1 = 2 seconds    |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| Don't wish to honor   | Send CAN                | exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | RB1 | WaitBark |1| Got ACK               | Rcv Bark Packet (*1)    | RB2 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| Got ETB               | Report done             | exit|
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| Got ENQ               | Send ETB                | RB0 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |4| T1 expired            | Purge Input, Send ENQ,  | RB1 |
    |     |          | |                       |   Set T1 = 2 seconds    |     |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |5| 20 seconds in RB1     | Hang Up, Report error   | exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | RB2 | AckBark  |1| Bark Pkt Rcvd Good    | Send ACK                | RB3 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| Bark Pkt Rcv Error    | Send NAK                | RB1 |
    +-----+----------+-+-----------------------+-------------------------+-----+
    | RB3 | WaitStrt |1| Got 'C' or NAK        |                         | RB4 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |2| No data for 3 seconds | Send ACK                | RB3 |
    |     |          +-+-----------------------+-------------------------+-----+
    |     |          |3| 15 seconds in RB3     | Hang Up, Report Error   | exit|
    +-----+----------+-+-----------------------+-------------------------+-----+
    | RB4 | SendFile |1| Can snd requested file| (Batch Send File BS0)   | RB0 |
    |     |   (*2)   +-+-----------------------+-------------------------+-----+
    |     |          |2| Can't send file       | Send EOT                | RB0 |
    `-----+----------+-+-----------------------+-------------------------+-----'
    *1 - If SUB (16H) received before ETX go to RB0 to resync bark receive

    *2 - While deciding if file exists, and if the password allows it to be
         sent etc., a NUL may be sent to buy 20 seconds more on the timeout
         on the other end if it is using the SEAlink extended FTS-0001
         specification protocol.  Sending a NUL is harmless for a strict
         FTS-0001 session, but will not buy more time.