Document: FSC-0066
Version:  002
Date:




                          Type 3Binary:  A proposal
                          =========================

                                  Mark Kimes
                               FidoNet 1:380/16           




Status of this document:

     This FSC suggests a proposed protocol for the FidoNet(r) community,
     and requests discussion and suggestions for improvements.
     Distribution of this document is unlimited.  Information in this
     document is freely usable and adaptable by any and all parties.

     Fido and FidoNet are registered marks of Tom Jennings and Fido
     Software.




Specifications for type 3binary mail format:
===========================================

Type 3binary is a new form of mail for Fidonet Technology Networks
(FTNs).  I've tried to design it to be simple to program, reasonably
cheap to implement, flexible, extensible, compact and powerful.


Chunks:
------

The basic unit of type 3binary mail is a chunk.  A chunk looks like
this:

          +-------------------------------------+
     +----+ 2-byte integer length (type + data) | (A 2-byte integer is
     |    +-------------------------------------+  a signed integer in
     |   /| 2-byte unsigned integer type        |  Intel format, giving
     +--+ +-------------------------------------+  a length range of
         \| length - 2 of data (may be none)    |  2-32767 (0 is unused).
          +-------------------------------------+  binary numbers in
          | pad byte for alignment if required  |  3binary are always Intel
          +-------------------------------------+  format.)

Chunks are usually contained (as "subchunks") within a "container", or
"master", chunk that has the form:

          +-------------------------------------+
    +-----+ 2-byte integer length (type + data) |
    |     +-------------------------------------+
    |    /| 2-byte unsigned integer type        |
    |   / +-------------------------------------+
    +--+  | 4-byte long integer giving total    |
        \ | length of all following subchunks   +----+
         \| complete.                           |    |
          +-------------------------------------+\   |
          | (subchunks...)                      | +--+
          +-------------------------------------+/

Predefined chunk types:
----------------------

 Quick table:
 -----------

 Mnemonic  VAL Where  Data format
 --------  --- -----  -----------
*EOP       0    END   None (end of packet indicator)
*FROM      1   BOTH   FTN address in packet, name@FTN address in msg
 TO        2   BOTH   [FTN address in packet,] name[@FTN address] in msg
 SUBJECT   3    MSG   Text hinting at topic of message
*ID        4    MSG   4-byte long integer
 REF       5    MSG   4-byte long integer followed by FTN address.
*DATE      6    MSG   Packed date
 ATTRIB    7   BOTH   4-byte integer (bit field; see below)
 PASSWORD  8   BOTH   8-bit text, case sensitive
*PRODUCT   9    PKT   8-bit text, case insensitive
 ECHO      10  BOTH   8-bit text, case insensitive
 MSG       11 TWEEN   4-byte long integer (length of total msg)
 TEXT      12   MSG   8-bit text
 ORIG      13  BOTH   Origin address in native network's format
 ORIGID    14   MSG   Origin network's form of message identifier
 FONT      15   MSG   Text describing recommended font style
 CHARSET   16   MSG   Text:  Character set identifier (including 16-bit
                      character sets)
 RICH      17   MSG   Richly formatted 8-bit text
 SUB       18  BOTH   Subtopic chunk (use with ECHO, as for ECHO)
 GROUP     19  BOTH   As for ECHO, but for Groupmail-like technology
 ATTACH    20   MSG   Text giving name of a file that should follow msg
 DEST      21   BOTH  Destination address in native network's format
 QUOTE     22   MSG   Original user's name and quoted text
 GLOBAL    23  TWEEN  4-byte long integer (length of global chunks following)
 ENCRYPT   24   MSG   Encryption method and encrypted text
 ADD       25   MSG   Add an ECHO area.
 DROP      26   MSG   Drop an ECHO area.
 REPORT    27   MSG   Report on ECHO areas.
 PKT       28 TWEEN   4-byte long integer (length of total packet header)

 * = required field.

 Notes:
 -----
 o Even when text is case insensitive, case should be preserved.
 o Addresses are always in text, and always given in full.
 o A full FTN address is in the form:
      domain[.sub[.sub]]#zone:net/node[.point]
   Multiple levels of subdomains are possible.  The rest of the address
   after '#' can be considered internally as one subdomain if desired.
   Node and point are decimal representations of 2-byte unsigned
   integers in the range 0-65534 (if point is 0 it should be omitted).
   Zone and net are decimal representations of 2-byte unsigned integers
   in the range 1-65532.  Domains and subdomains are case insensitive
   alphanumeric text, and each "part" (separated by periods) is
   significant to 8 characters (preserve what you get though, please).
 o Name@FTN address form is:
      user name@Full_FTN_address
 o Note that the characters '#' and '@' are illegal in a user name.
 o Address in TO field may be omitted for broadcast mail.  If user name
   is missing, assume message is addressed to "All."  TO chunk may be
   omitted in packet header if packet not designed to forward en masse.
   Multiple TO chunks may be present and would be considered a request
   to send the message to each listed address.
 o "8-bit text" just means that all 8 bits in a byte are useable.
   It doesn't mean that a CHARSET can't change this to use 16-bit
   characters or something else "strange," just that all 8 bits in bytes
   are useable.  In the absence of a CHARSET chunk, ISO-8859-1 (Latin-1)
   should be assumed.
 o Note that a CHARSET may be required before other text-based chunks,
   even in a header.  This allows, for example, "user name" to contain
   defined characters not in the default character set.
 o "TWEEN" chunks are "container" chunks; their data indicates the length
   of "subchunks" that follow and are contained within the master
   "TWEEN" chunk.  MSG, PKT and GLOBAL chunks are masters.  Other
   masters may be encountered as new chunks are defined.  At a minimum,
   new master chunks should contain FROM and TO subchunk information to
   allow an older implementation to route the chunks, even if ignorant
   of their content.
   


Chunk breakdown:
===============                                                 Chunk class:
                                                                -----------
EOP (marks end of packet):                                      n/a
          +---------------------------------------------------+
  Len     | 2-byte integer length (always 2)                  |
          +---------------------------------------------------+
  Type    |     00 (EOP type indicator)                       |
          +---------------------------------------------------+

FROM (indicates FTN origin of packet or message):               CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     01 (FROM type indicator)                      |
          +---------------------------------------------------+
  Data    | FTN origin address in text                        |
          | (FTN address in packet,                           |
          |  user name@FTN address in message)                |
          | This information is required                      |
          +---------------------------------------------------+

TO (indicates FTN destination of packet or address):            CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     02 (TO type indicator)                        |
          +---------------------------------------------------+
  Data    | FTN destination address in text                   |
          | (FTN address in packet,                           |
          |  user name@FTN address in message)                |
          | may be omitted or partial (name only) if ECHO     |
          | chunk is active.  Required for netmail.           |
          +---------------------------------------------------+

SUBJECT (indicates something about the message's topic):        CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     03 (SUBJECT type indicator)                   |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          +---------------------------------------------------+

ID (unique message identifier):                                 CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     04 (ID type indicator)                        |
          +---------------------------------------------------+
  Data    | 4-byte long integer                               |
          | It is up to the originator of the message to use  |
          | a number which, when combined with the FROM       |
          | chunk, forms a unique ID for this message for a   |
          | period of at least one year.                      |
          +---------------------------------------------------+

REF (reference identifier):                                     CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     05 (REF type indicator)                       |
          +---------------------------------------------------+
  Data    | 4-byte long integer.  This corresponds to the ID  |
          | of the message to which this is a reply.          |
          +---------------------------------------------------+
          | FTN address in text                               |
          | This corresponds to the FROM address (less user   |
          | name) of the message to which this is a reply.    |
          +---------------------------------------------------+

DATE (date of message):                                         CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     06 (DATE type indicator)                      |
          +---------------------------------------------------+
  Data    | A binary structure with the following format:     |
          +---------------------------------------------------+------------+
          | 2-byte unsigned int year                                       |
          +----------------------------------------------------------------+
          | unsigned byte month (1-12)                                     |
          +----------------------------------------------------------------+
          | unsigned byte day-of-month                                     |
          +----------------------------------------------------------------+
          | unsigned byte hour                                             |
          +----------------------------------------------------------------+
          | unsigned byte minute                                           |
          +----------------------------------------------------------------+
          | unsigned byte second                                           |
          +----------------------------------------------------------------+
          | byte pad for alignment                                         |
          +----------------------------------------------------------------+
          | 2-byte signed int gmt offset (15 min increments, -32767 = n/a) |
          +----------------------------------------------------------------+

ATTRIB (bitmapped attribute field):                             CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     07 (ATTRIB type indicator)                    |
          +---------------------------------------------------+
  Data    | 4-byte long integer (bit-mapped field)            |
          | Defined bits:                                     |
          +---------------------------------------------------+---+
          | 0 = PRIVATE in message header,                        |
          |     "en masse forward okay" in packet header          |
          +-------------------------------------------------------+
          | 1 = Audit trail requested; use sparingly              |
          +-------------------------------------------------------+
          | 2 = Return receipt requested; use sparingly,          |
          |     netmail only                                      |
          +-------------------------------------------------------+

PASSWORD (password protection at packet/message level):         CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     08 (PASSWORD type indicator)                  |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          +---------------------------------------------------+

PRODUCT (name of program producing the packet):                 CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     09 (PRODUCT type indicator)                   |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          +---------------------------------------------------+

ECHO (echo area tag identifying a conference):                  CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     10 (ECHO type indicator)                      |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          +---------------------------------------------------+

MSG (message chunks preface):                                   CONTAINER
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     11 (MSG type indicator)                       |
          +---------------------------------------------------+
  Data    | 4-byte long indicating total length of all        |
          | following chunks that comprise message            |
          | note this allows "skipping" a message in one bite |
          | or loading entirely into memory in one bite for   |
          | processing without further disk access.           |
          +---------------------------------------------------+

TEXT (generic message text):                                    BODY
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     12 (TEXT type indicator)                      |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | This is similar to what's in a type 2 message     |
          | body.  As with type 2, text is free flowing with  |
          | carriage returns to terminate paragraphs.         |
          | Unlike type 2, no "soft-crs" and linefeeds.       |
          +---------------------------------------------------+

ORIG (origin address in native network's format):               CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     13 (ORIG type indicator)                      |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | When a message is gated into an FTN, this field   |
          | is used to preserve the "true" origin address for |
          | purposes of generating a reply back through the   |
          | gate to the originator.                           |
          +---------------------------------------------------+

ORIGID (original message identifier in native network's format): CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     14 (ORIGID type indicator)                    |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | When a message is gated into an FTN, this field   |
          | is used to preserve the original unique message   |
          | identifier (if one was used) for purposes of      |
          | reply linking and as an adjunct to dupe detection |
          +---------------------------------------------------+

FONT (font change):                                             BODY
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     15 (FONT type indicator)                      |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | This would describe the recommended font to use   |
          | when displaying subsequent items.  I leave this   |
          | vague; we need to adopt an extant standard, if    |
          | possible.  If nothing else, pointsize.style.mod   |
          |        (example:  10.Helvetica.Bold)              |
          | No font is defined at the beginning of a message, |
          | but you can use a "global" chunk to set a         |
          | "default" font.  A font, once defined, remains in |
          | effect until the end of the message or until      |
          | another FONT chunk is encountered.  As is the     |
          | case with all global chunks, if a global FONT     |
          | chunk is defined and overridden within a message  |
          | by a message-local FONT chunk, the font reverts   |
          | to the globally defined font when the message     |
          | ends.                                             |
          +---------------------------------------------------+

CHARSET (character set change):                                 CTRL/BODY
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     16 (CHARSET type indicator)                   |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | This would describe the recommended character set |
          | to use when displaying subsequent items.  In the  |
          | absence of this chunk type, 8-bit ISO 8859-1 is   |
          | assumed at the start of a message.  Note this     |
          | should be able to be used to introduce multi-byte |
          | characters, too.  I leave this vague, again,      |
          | because this is outside my one-language ignorant  |
          | American expertise.  We should adopt extant       |
          | standards , if possible.  You can use a "global"  |
          | chunk to set a default character set for          |
          | subsequent messages.                              |
          | A character set, once defined in a message,       |
          | remains in effect until the end of the message or |
          | another CHARSET chunk is encountered.             |
          +---------------------------------------------------+

RICH (richly formatted text):                                   BODY
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     17 (RICH type indicator)                      |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          +---------------------------------------------------+

SUB (subtopic):                                                 CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     18 (SUB type indicator)                       |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | Used with ECHO type, can be used to selectively   |
          | subdivide conferences.  Multiple subtopics may be |
          | separated by semi-colons.                         |
          +---------------------------------------------------+

GROUP (Group area tag identifying a conference):                CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     19 (GROUP type indicator)                     |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | As for ECHO type, provided to ease migrating of   |
          | type 2 groupmail technology                       |
          +---------------------------------------------------+

ATTACH (file attached to a message or packet):                  CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     20 (ATTACH type indicator)                    |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | Name of a file that should follow the message or  |
          | packet.  No drive or path indicators should be    |
          | present, just a simple filename.                  |
          | The message probably describes the file.          |
          +---------------------------------------------------+

DEST (destination address in native network's format):          CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     21 (DEST type indicator)                      |
          +---------------------------------------------------+
  Data    | 8-bit Text                                        |
          | Used to pass the "true" destination address of a  |
          | message being sent to a non-FTN network to the    |
          | gateway software.                                 |
          +---------------------------------------------------+

QUOTE (quoted text):                                            BODY
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     22 (QUOTE type indicator)                     |
          +---------------------------------------------------+
  Data    | 2-byte integer, length of user's name             |
          +---------------------------------------------------+
          | 8-bit Text, user's name                           |
          | If a previous QUOTE chunk was present in the      |
          | message and the same user is being quoted, the    |
          | user name may be empty for subsequent QUOTE       |
          | chunks.                                           |
          +---------------------------------------------------+
          | 1-byte pad if required for alignment              |
          +---------------------------------------------------+
          | 2-byte integer, length of text                    |
          +---------------------------------------------------+
          | 8-bit Text                                        |
          +---------------------------------------------------+

GLOBAL (global chunks preface):                                 CONTAINER
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     23 (GLOBAL type indicator)                    |
          +---------------------------------------------------+
  Data    | 4-byte long indicating total length of all        |
          | following chunks that comprise global chunks.     |
          +---------------------------------------------------+

ENCRYPT (encrypted text):                                       BODY
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     24 (ENCRYPT type indicator)                   |
          +---------------------------------------------------+
  Data    | 2-byte integer, encryption method description     |
          +---------------------------------------------------+
          | 8-bit Text, method of encryption (probably        |
          | the name of the software package used to encrypt  |
          | and decrypt the following text).  If a previous   |
          | ENCRYPT chunk was present in the message and the  |
          | same encryption method was used, the method of    |
          | encryption may be empty for subsequent ENCRYPT    |
          | chunks.                                           |
          +---------------------------------------------------+
          | 1-byte pad if required for alignment              |
          +---------------------------------------------------+
          | 2-byte integer, length of encrypted text          |
          +---------------------------------------------------+
          | Encrypted data                                    |
          +---------------------------------------------------+

ADD (add ECHO area):                                            CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     25 (ADD type indicator)                       |
          +---------------------------------------------------+
  Data    | 8-bit Text, tag of conference to add.             |
          +---------------------------------------------------+

DROP (drop ECHO area):                                          CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     26 (DROP type indicator)                      |
          +---------------------------------------------------+
  Data    | 8-bit Text, tag of conference to drop.            |
          +---------------------------------------------------+

REPORT (report on ECHO areas):                                  CONTROL
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     27 (REPORT type indicator)                    |
          +---------------------------------------------------+
  Data    | 8-bit Text, special request, optional.            |
          +---------------------------------------------------+

PKT (packet header preface):                                    CONTAINER
          +---------------------------------------------------+
  Len     | 2-byte integer length (2 + length of data)        |
          +---------------------------------------------------+
  Type    |     28 (PKT type indicator)                       |
          +---------------------------------------------------+
  Data    | 4-byte long indicating total length of all        |
          | following chunks that comprise packet header.     |
          +---------------------------------------------------+



Chunk classes:
-------------

Chunks of class CONTROL should precede chunks of class BODY to ensure
that control information is known before large blocks of data show up.
This allows processors to make decisions about what to do with the
message before any paging might have to take place, if the processor
is designed to require paging.  Chunks of class CONTAINER are container,
or master, chunks that have as data a long 4-byte integer giving the
length of all following (contained) subchunks.


Experimental and strippable chunk types:
---------------------------------------

Chunk types above 41951 are reserved for experimental use.  Experimental
chunks, and chunk 41951, may be stripped during passthrough; all other
chunks should be preserved, even if not understood, during passthrough.
Apply to the FTSC if you feel you have a chunk that deserves
"canonization."  Minimum requirements for canonization are a unique
purpose, existing, complete, published specifications covering the use
and contents of the new chunk type, and backward compatibility with this
specification.


GLOBAL chunks:
-------------

The GLOBAL chunk is followed by (data) bytes of other chunks
(subchunks).  These "global" chunks are used for information that may be
repeated in several messages.  For example, if several messages are all
from the same user and system, a "global" TO chunk might be used instead
of independent TO chunks in each message.  For another, messages in
various echos might be grouped with "global" ECHO chunks.  In yet
another, default CHARSET and FONT chunks might be set up.  To cancel a
previously defined "global" chunk, issue it again with no data.  To
cancel all defined "global" chunks, use a GLOBAL chunk followed by
(data) number of 0.  GLOBAL chunks may not occur _within_ messages, but
must be situated _between_ messages, just like MSG chunks themselves.

Chunks in the MSG override "global" chunks, but it would probably be
preferable to omit one or the other in most cases.  Obviously, not all
message chunks lend themselves to being global; ID and DATE chunks are
good examples.  Global TEXT chunks, if present, should be appended to
the end of messages.  Other chunks would normally be prepended to the
portion of the message where they belong (a quick way to set CHARSET and
FONT defaults).

If something similar to type 2's SEEN-BYs _must_ be used (to protect
fully enclosed polygon topologies, for instance), use a GLOBAL chunk
containing a "global" chunk type of 41951 (note that type will ensure
stripping at all stops).  I won't describe how you'd do it here, but I
suggest you use full addresses separated by something strange like a
semicolon.


Intent:
------

The limit on the size of data + type to 32767 bytes is to ensure that
even limited horsepower/resource machines can implement 3binary mail.
Since several chunks can be combined to create very large messages, this
is no severe limitation.  It is the intent of these specifications that
chunks always be aligned on word (two byte) boundaries.  Aligning on
four byte boundaries and using four-byte integers for length and type
would give a slight performance improvement on 32-bit machines/operating
systems, but at least double the overhead of a chunk and make it harder
to implement on lesser machines.  Since the goal is communication, this
is to be avoided.


Packet parts -- an overview:
===========================

An extremely simplified diagram of a typical 3binary packet looks like:

 +-----------------------------------------------+
 | 0x0003  (3binary packet identifier)           |
 +-----------------------------------------------+
 | PKT chunk                                     |
 +-----------------------------------------------+
 | [MSG [and GLOBAL] chunks.....]                |
 +-----------------------------------------------+
 | EOP chunk                                     |
 +-----------------------------------------------+


Packet Header:
-------------

A type 3binary packet always begins with a 2-byte integer containing
the binary number 3 to aid in identifying packets at the receiving node.
This is followed immediately by a PKT chunk containing the chunks of the
packet header.  A PKT chunk has, as data, the length of the entire
packet header that follows, excluding itself, in the form of a long
(4-byte) integer.  A header should contain at least a FROM chunk,
possibly a TO chunk or an ECHO (or GROUP) chunk, and a PRODUCT chunk
(and these chunks should be as close to the top of the header as
possible).  PASSWORD, ORIG and ATTRIB chunks might also be used.  Note
that if an ECHO (or GROUP) chunk is used in the header, all the messages
in the packet are for that echo area, and no TO chunk should be present
in the header, no ECHO chunks are required in the messages, and message
TO chunks can be only a user name without address.


Message Header:
--------------

A MSG chunk contains the chunks that make up a message.  The MSG chunk
has, as data, the length of the entire message that follows, excluding
itself, in the form of a long (4-byte) integer.  After this come FROM,
TO, DATE and ID chunks and perhaps other control class chunks such as
SUBJECT, ORIG, ORIGID, DEST, REF and so on.  A CHARSET chunk might also
be appropriate.

Note that a TO chunk without a user name, or a missing TO chunk, would
mean the message is addressed to "All".  A FROM chunk without a user
name might be considered from "Sysop," but this wouldn't be a good
habit.  A FROM address is always required.  A TO address is required for
netmail.  DEST and ORIG addresses are used when gating messages from
foreign (non-FTN) networks.  FROM, TO, ID and ECHO/GROUP chunks (as
applicable) should appear as close to the top of a message as possible.


Message Body:
------------

Following the message header comes the message body in the form of none
or more body class chunks.  TEXT, FONT, CHARSET, ENCRYPT, QUOTE and RICH
chunks might be included here.  Order of chunk appearance can be
important; fonts or character sets may be changed for specific sections
of text, for example.  After the message body chunk(s) will be another
MSG chunk, a GLOBAL chunk, or an EOP chunk signalling the end of the
packet.  Future enhancements will probably bring GRAPHIC, IMAGE and
SOUND chunks as well as others I haven't even considered yet.  Your
input is welcomed.


It's important to note that there's no clear break between the header
and body of a message.  This causes no problems and allows flexibility
for future, yet unthought of methodology.  Remember, during passthrough
of messages, just copy chunks using FROM and TO to route as required.
During import, ignore anything you don't understand.


A fleshed-out diagram of a sample "theoretical" packet:

 +-----------------------------------------------+
 | 0x0003  (3binary packet identifier)           |
 +===============================================+
 | PKT chunk                                     +--+
 +-----------------------------------------------+  |
 | FROM chunk                                    |  |
 +-----------------------------------------------+  |
 | TO chunk                                      |  |
 +-----------------------------------------------+  |
 | PRODUCT chunk                                 |  |
 +===============================================+--+
 | GLOBAL chunk                                  +--+
 +-----------------------------------------------+  |
 | FROM chunk                                    |  |
 +-----------------------------------------------+  |
 | ECHO chunk                                    |  |
 +===============================================+--+
 | MSG chunk                                     +--+
 +-----------------------------------------------+  |
 | TO chunk (user name only)                     |  |
 +-----------------------------------------------+  |
 | ID chunk                                      |  |
 +-----------------------------------------------+  |
 | REF chunk                                     |  |
 +-----------------------------------------------+  |
 | SUBJECT chunk                                 |  |
 +-----------------------------------------------+  |
 | TEXT chunk                                    |  |
 +===============================================+--+
 | MSG chunk                                     +--+
 +-----------------------------------------------+  |
 | TO chunk (user name only)                     |  |
 +-----------------------------------------------+  |
 | ID chunk                                      |  |
 +-----------------------------------------------+  |
 | REF chunk                                     |  |
 +-----------------------------------------------+  |
 | SUBJECT chunk                                 |  |
 +-----------------------------------------------+  |
 | TEXT chunk                                    |  |
 +===============================================+--+
 | GLOBAL chunk                                  +--+
 +-----------------------------------------------+  |
 | ECHO chunk (empty)                            |  |
 +===============================================+--+
 | MSG chunk                                     +--+
 +-----------------------------------------------+  |
 | TO chunk (w/ address; netmail now)            |  |
 +-----------------------------------------------+  |
 | ID chunk                                      |  |
 +-----------------------------------------------+  |
 | REF chunk                                     |  |
 +-----------------------------------------------+  |
 | SUBJECT chunk                                 |  |
 +-----------------------------------------------+  |
 | TEXT chunk                                    |  |
 +-----------------------------------------------+  |
 | TEXT chunk                                    |  |
 +===============================================+--+
 | MSG chunk...etc.                              |
 ~                                               ~
 +===============================================+
 | EOP chunk (end of packet)                     |
 +-----------------------------------------------+


Naming conventions:
------------------

To assure that there are no conflicts between FTN type 2 mail and type
3binary mail, a different naming scheme for packets and bundles is used.
Note this only discusses filenames as sent to the receiving system; how
or what you store them as locally isn't the concern of this
specification.

"Raw" 3binary packets are named 3PAKT###.###.  Archived 3binary packets
(bundles) are named 3BNDL###.###.  '#' in these filenames refers to
decimal digits (0-9).  Case is not sensitive.  Where multiple files are
present, such as multiple packets within a bundle, the filenames should
be such that ASCII sorting puts them into the appropriate order for
sequential processing.



Comparing 3binary to Type 2:
===========================

Raw type 3binary packets are always smaller than type 2 packets.  You
can test this for yourself by running 3BTO2.EXE on the sample 3binary
packet 3PAKT000.000:
  12950           3PAKT000.000
	14512 					test.pkt
Compression tends to negate much of this advantage, however.
Conventional compression likes lots of text.

(Note that the above test is biased in type 2's favor.  The sample
 3binary packet was created nastily from my message base; no GLOBAL
 chunks were used.  Only tiny SEEN-BYs, minimal tear and Origin lines
 and no PATH lines are in test.pkt.  Normally, the size difference would
 be greater.)

Processing of 3binary packets is far more robust than processing type 2
packets, and is more easily handled on machines with limited resources.
The simple sample code in the archive is limited only by available
memory.  Slight modifications would allow limitation to available disk
space (on non-VM systems where there is a difference).

Type 3binary has the potential to carry data other than simple text,
such as sound and graphics.  It can, in fact, carry things other than
messages (if someone comes up with an idea for something else worthwhile
to carry).	Type 2 doesn't have this capability.




Mark Kimes
Fidonet#1:380/16.0
(318)222-3455 data USA