Document: FSC-0045
Version:  001
Date:     17-Apr-90





                                 A Proposal
                                    for
                         A New Packet Header Format
                               Thom Henderson
                            1:107/542.1@FidoNet
                               April 17, 1990





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.

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




Provisions have been made for storing full five-dimensional addresses (i.e.
zone, net, node, point, and domain) in a packed message such that it is 
possible (albeit somewhat clumsily) to extract a full five dimensional 
origin and destination for any message.  This has not, however, been 
extended to packet headers.  It would be useful for various reasons, such 
as mail pickpus and password protection of mail links, to be able to 
quickly and easily extract similar five dimensional addresses from a packet 
header.  This is a proposal for a packet header structure that would make 
that possible.


The proposed packet header structure is as follows:

    Offset   Width     Description
    ======   =====     ===========
         0       2     Originating node number
         2       2     Destination node number
         4       2   * Originating point number
         6       2   * Destination point number
         8       8     Reserved, must be zero
        16       2     Packet sub-version (2)
        18       2     Packet version (2)
        20       2     Originating network
        22       2     Destination network
        24       1     Product code
        25       1     Product revision level
        26       8     Password
        34       2   * Originating zone
        36       2   * Destination zone
        38       8   * Originating domain
        46       8   * Destination domain
        54       4     Product specific data
        58     ---     Start of first packed message

                     * Field only guaranteed accurate in a type 2.2 header


All numbers are in decimal.  The point of this proposed structure is that 
it is backwards compatible.  All significant fields of a normal type 2 
packet header are preserved and are in the same places.  The following data 
fields of a type 2 packet have been discarded and replaced with new 
informational content:

    Packet creation date (6 bytes)
    Packet creation time (6 bytes)
    Packet baud rate (2 bytes)
    Reserved for future use (16 bytes)

The field formerly occupied by the packet baud rate has been replaced by 
the packet sub-version number.  If this number is set to "2" (an impossible 
baud rate), then that indicates a type 2.2 packet header, and the fields 
marked above with an asterisk become valid.  If this field contains 
anything other than a 2, then only the original type 2.0 data may be 
regarded as accurate.