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The field formerly occupied by the packet baud rate has been replaced by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.
