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<TITLE>A Proposed Type-2 Packet Extension.</TITLE>
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<PRE>
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Document: FSC-0048
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Version: 002
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Date: 21-Oct-90
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A Proposed Type-2 Packet Extension
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Jan Vroonhof
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2:281/1.12@fidonet
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Oct 21, 1990
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Status of this document
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=======================
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This FSC suggests a proposed protocol for the FidoNet(r)
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community, and requests discussion and suggestions for
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improvements. Distribution of this document is unlimited.
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Fido and FidoNet are registered marks of Tom Jennings and Fido
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Software.
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Purpose
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=======
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The final goal of this document is to become a widely used
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standardised extension to FTS-0001, like FTS-0006, 0007 and
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0008 are, and provide an elegant way to switch to a new
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bundling method without requiring major effort or breaking
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anything.
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Prologue
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========
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The main thing that needs stressing is that the additions
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covered by this document are FULLY (I repeat FULLY) BACKWARDS
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COMPATIBLE with FTS-0001 (and other existing standards and
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practices in FidoNet and WhatEverOtherNets that I know of).
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When I say "backwards compatible" I mean that problems it would
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create already exist in the current FTS-0001 system (e.g.
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zone conflicts when dealing with a non compliant system). In
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short it only corrects some flaws in FTS-0001 WITHOUT
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generating new ones.
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In this document I have tried to stay as much as possible on
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the paths of existing practices. Therefore I think
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implementation of the additions it proposes will not be too
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hard.
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! Prologue to revision 2
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! ======================
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! Revision 2 of this document reserves a bit in the
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! CapabilityWord for one bundle type already in use outside of
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! FidoNet, RFC-822. A small change was made to the "receiving"
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! flowchart in order to ensure compatibility with FSC-0039.004.
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! In the process a lot of errors and omissions in the spelling,
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! credits etc. were corrected.
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===============
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! All references in the following to FSC-0039 are to Revision 1
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! of that document.
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My thoughts on FSC-0039 and FTS-0001 rev 12
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===========================================
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First, revision 12 of FTS-0001 introduced the term "(some
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impls)" to indicate that some implementations used their own
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! extensions to FTS-0001 (Note that in later revisions this was
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! changed to "optional"). The problem is that this info cannot be
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relied upon, because there is no way to actually validate the
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data. One can only check whether the values of these fields are
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in the range of valid values and hope for the best.
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Second, FSC-0039 introduced the idea of having a bitfield
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(called the Capability Word) indicating whether extension data
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was valid. Through the Capability Word, it also made it
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possible to indicate the ability to support other, non type 2,
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packets, thus allowing for flexible migration towards type 3.
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It also documented the addressing extensions used by various
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programs.
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However, FSC-0039 has two flaws:
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1. One cannot be sure the bitfield is zero because other
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implementations might use this field for their own purposes.
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Therefore this document includes a second validation copy
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for the Capability Word (CW hereafter). This copy allows the
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FSC-xxxx compliant software to validate the CW by comparing
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the two. The chance of some junk portraying itself as a CW
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is significantly reduced by this.
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! Please note that the validation copy is byte swapped
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! compared to the normal capability word. While this started
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! out as a typo, I decided to leave it in as it introduces
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! some extra safety, without requiring much extra code effort.
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! In later revisions of FSC-0039, Mark adopted this idea of a
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! validation copy too and eliminated the problem.
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2. Although FSC-0039 provides a way to make packet headers 4D
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it is not backwards compatible. It cannot be used in FTS-
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0001 sessions to unknown systems, making FidoNet still not
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totally 4D capable. Although it implements fields for zone
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and point number, an FTS-0001 compliant application is not
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required to look at these fields. When a point mails using
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these fields to implement its 4D address, a system only
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looking at the net/node info, as is required by FTS-0001,
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still sees it as a boss node, causing the obvious problems.
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This document provides a way for transparent point handling,
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using a technique already exploited by many mailers
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internally. It will allow this document to be implemented
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and used by mailers not supporting it. At the same time the
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danger that a point is seen as the boss node is eliminated.
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It does NOT provide full inter-zone backwards compatibility,
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but that is not needed as badly, as problems are not yet too
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great. Any measures to ensure backwards compatibility in
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this area might harm communication with non-supporting
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programs, when the old system could handle the situation.
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Packet Header
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=============
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The "|" character is used to indicate extensions documented in
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FTS-0001 revision 12, the ":" character indicates those
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documented here and in FSC-0039.
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Offset
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dec hex
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.-----------------------------------------------------.
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0 0 | origNode (low order) | origNode (high order) |
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+--------------------------+--------------------------+
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2 2 | destNode (low order) | destNode (high order) |
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+--------------------------+--------------------------+
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4 4 | year (low order) | year (high order) |
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+--------------------------+--------------------------+
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6 6 | month (low order) | month (high order) |
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+--------------------------+--------------------------+
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8 8 | day (low order) | day (high order) |
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+--------------------------+--------------------------+
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10 A | hour (low order) | hour (high order) |
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+--------------------------+--------------------------+
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12 C | minute (low order) | minute (high order) |
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+--------------------------+--------------------------+
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14 E | second (low order) | second (high order) |
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+--------------------------+--------------------------+
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16 10 | baud (low order) | baud (high order) |
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+--------------------------+--------------------------+
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18 12 | 0 | 2 | 0 | 0 |
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+--------------------------+--------------------------+
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20 14 | origNet (low order) | origNet (high order) |
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: | Set to -1 if from point |
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+--------------------------+--------------------------+
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22 16 | destNet (low order) | destNet (high order) |
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+--------------------------+--------------------------+
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| 24 18 | ProductCode (low order) | Revision (major) |
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| +--------------------------+--------------------------+
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| 26 1A | password |
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| | 8 bytes, null padded |
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| +--------------------------+--------------------------+
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|: 34 22 | origZone (low order) | origZone (high order) | }
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| +--------------------------+--------------------------+ } As in
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|: 36 24 | destZone (low order) | destZone (high order) | } QMail
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: +--------------------------+--------------------------+
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: 38 26 | AuxNet (low order) | AuxNet (high order) |
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: +--------------------------+--------------------------+
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: 40 28 | CWvalidationCopy (high) | CWvalidationCopy (low) |
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: +--------------------------+--------------------------+
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: 42 2A | ProductCode (high order) | Revision (minor) |
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: +--------------------------+--------------------------+
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: 44 2C | CapabilWord (low order) | CapabilWord (high order) |
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: +--------------------------+--------------------------+
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: 46 2E | origZone (low order) | origZone (high order) | }
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: +--------------------------+--------------------------+ } As in
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: 48 30 | destZone (low order) | destZone (high order) | } FD etc
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: +--------------------------+--------------------------+
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: 50 32 | origPoint (low order) | origPoint (high order) | }
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: +--------------------------+--------------------------+ } As in
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: 52 34 | destPoint (low order) | destPoint (high order) | } FD etc
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: +--------------------------+--------------------------+
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: 54 46 | Product Specific Data |
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: + +
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: | 4 Bytes |
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+--------------------------+--------------------------+
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58 3A | zero or more |
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~ packed ~
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| messages |
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+--------------------------+--------------------------+
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| 0 | 0 | 0 | 0 |
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'-----------------------------------------------------'
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Packet = PacketHeader { PakdMessage } 00H 00H
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PacketHeader = origNode (* of packet, not of messages in packet *)
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destNode (* of packet, not of messages in packet *)
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year (* of packet creation, e.g. 1986 *)
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month (* of packet creation, 0-11 for Jan-Dec *)
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day (* of packet creation, 1-31 *)
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hour (* of packet creation, 0-23 *)
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minute (* of packet creation, 0-59 *)
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second (* of packet creation, 0-59 *)
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baud (* max baud rate of orig and dest *)
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PacketType (* old type-1 packets now obsolete *)
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origNet (* of packet, not of messages in packet
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set to -1 if orig=point *)
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destNet (* of packet, not of messages in packet *)
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+ productCode Lo (* 0 for Fido, write to FTSC for others *)
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|+ serialNo Maj (* binary serial number (otherwise null) *)
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| password (* session pasword (otherwise null) *)
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| origZone (* zone of pkt sender (otherwise null) *)
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| destZone (* zone of pkt receiver (otherwise null) *)
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| auxNet (* contains Orignet if Origin is a point *)
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+! Bytesw. CWvalidationCopy (* Must be equal to CW to be valid *)
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+ ProductCode Hi
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+ revision Minor
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+ origZone (* zone of pkt sender (otherwise null) *)
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+ destZone (* zone of pkt receiver (otherwise null) *)
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+ ProdData (* Product specific filler *)
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When the two copies of the CW match they can be asumed to be
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valid and used.
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Stone-Aged: Old FTS-0001
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Type-2+ : Old FTS-0001 plus changes indicated by "|" and ":"
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are valid
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A Type-N Bundle will always advertise its capabilities in the
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CW regardless of the type being sent. As shown in the example
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below, the CW allows Type-N processors to automatically track
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the capability of your system. Again, in cases where a stone-
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age processor is being used, this field will be ignored, and in
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the unusual event that it is not ignored, and is somehow
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harmful to the far system, the Type-N processor can be
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configured to send a CW of 0.
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The format of the Capability Word is designed to support up to
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15 future bundle types, and is bit-mapped to facilitate the
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easy determination of the maximum common level supported
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between two nodes:
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msb Capability Word lsb
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Node Supports ------------FTSC Type Supported **)------------
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U 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2+
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2+,3, and 7 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 1
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2+,3, and 5 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1
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2+ (this Doc) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
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Stone Age 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
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! ^-- "U" Indicates nodes able to process RFC-822
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! bundles.
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** - In the example bit definitions only type 2,
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and the Stone-Age type, are defined now.
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The rest are to be concidered "reserved by
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FTSC".
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The receiving Type-N bundler would AND the two words, obtaining
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a word expressing the Types which are common to both the
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receiving and the sending system. The most significant Type
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will be used for future sessions, by default. Please note that
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this assumes that new bundling Types will be increasingly more
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efficient or in some way more beneficial. Because this may not
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always be the case, there should be a method provided to
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override the automatic upgrade, as illustrated above, should
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this ever happen.
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! N.B. The one bit left over (Msb) is now used as indicator for
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! RFC-822 type bundles. For info on RFC-822 please check out
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! the relevant documents themselves.
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! For a more explanatory text on using the CW to its full
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! potential, refer to the FSC-0039 text by Mark Howard.
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! Mark also gives some more rationale for the origional idea
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! of the CW.
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Generating Type-2+ bundles
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==========================
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Do we have a CW Does CW indicate
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stored for dest? YES ----> higher packets YES ---> Generate higher
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NO we support? packet
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| NO
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\|/ |
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+-----<----------------------+
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Fill header with all info
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\|/
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Are we sending from a point? (origPoint != 0) YES --+
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| |
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NO |
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| \|/
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| set AuxNet = OrigNet
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\|/ set OrigNet = -1
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+-----<----------------------------------------+
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Add Messages
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Terminate packet
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Send packet
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Receiving Type-2+ bundles
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=========================
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Receive Packet
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Packettype = 2 NO -------------> Process Type-Other
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YES
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CWcopies match NO --------+------> Treat as normal Stone-Age packet
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YES | |
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| | |
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Store CW /|\ |
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| | /|\
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CW is 0 YES --------------+ |
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NO |
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CW indicates support for 2+ NO --+
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YES
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! OrigPoint is not 0 and OrigNet = -1 YES -------+
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NO |
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| \|/
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! \|/ Set OrigNet is AuxNet
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+------<-----------------------------------+
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Process using added info
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Credits
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=======
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To Mark Howard, for introducing the idea of a CW in his FSC-
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0039 document and quite rightly pointing out one big omision
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in revision 1 of this document.
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To Rick Moore, for doing a good job in processing all these
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revisions by Mark and myself, and for his work for the FTSC in
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general.
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To Joaquim Homrighausen, for his contributions to FidoNet
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software in general, and especially for his time devoted to
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reading, discussing and implementing the ideas Mark and I
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introduced.
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To Andre van de Wijdeven, for producing and letting me beta
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test his TS-MM software, which in my opinion is the best point
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software around. (I'm not saying available, because it isn't
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:-()
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To john lots, for shipping this stuff to the US.
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To Jon Webb, for doing a much needed grammar and spelling
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check.
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To Bob Hartman, Vince Periello, Tom Jennings, Eelco de Graaff,
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aXel Horst, Arjen van Loon, jim nutt, Odinn Sorensen, David
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Nugent, Peter Janssens and many others, for making FidoNet
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what it is now, for me and for everybody.
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Epilog
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======
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So this it, now it's up to you to decide whether or not to
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implement it. A small change was made in the receivers
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flowchart and a small incompatibility with the later revisions
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of FSC-0039 was removed. That will ensure that FSC-0048 and
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FSC-0039 mailers can happily talk to each other....
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The best way to implement this would be to always support FSC-
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0048 on inbound trafic and generate FSC-0048 on outbound by
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default. A switch on a per-node basis will force your software
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to be FSC-0039 or even FSC-0001 only, and you will cover all
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bases.
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This can be done easily, as FSC-0048 is a superset of FSC-0039
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(The -1 thing on points being the difference) which in turn is
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a superset of FTS-0001 (CW). I'd be glad to get some feedback.
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You can put it in NET_DEV or netmail me.
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Jan Vroonhof (2:281/1.12@fidonet)
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</PRE>
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