| Document: FSC-0090
 | Version:  001
 | Date:     9 December, 1995
 |
 | Author:   David Nugent, 3:632/348@fidonet


 FTSC Issued Product Codes
 by David Nugent, December 9, 1995.


    For many years, the FidoNet Technical Standards Committee has been
    issuing product codes for use in FidoNet products used on the
    network (specifically those products responsible for creation and
    exchange of data over the network; products creating FidoNet type-2
    packets described in FTS-0001 and mailers talking together using
    FidoNet protocols described in FTS-0001, FTS-0006, FTS-0007 and
    FSC-0056. The primary purpose of using these product codes was not
    to create a registry of FidoNet related products, but to facilitate
    the identification of products responsible for network problems and
    providing a means by which authors might be contacted by the
    Committee should problems with a specific product be brought to its
    attention. Products issued with FTSC codes

    In respect to this objective, the results have only been partially
    successful. True, the product code list has been used from time to
    time both to identify aberrant products and also to contact authors
    and is still occasionally used for this purpose by both Committee
    members and others.

    The number of products which can be allocated FTSC product codes had
    some years ago exceeded expectation. Since FTS-0001 "type-2" FidoNet
    packets allocate a mere 8 bit field for the product code, that set
    the effective maximum number of products which could be allocated a
    product code to 256. All numbers had been allocated or reserved by
    early 1991.

    The issue was discussed at some length by the FTSC which debated
    first the worth of continuing to issue product codes, and secondly
    if the practice was to be continued, to effect changes in the
    FTS-0001 packet header format to accommodate at least a 16-bit (two-
    octet) product code. The first issue was resolved in favour of
    retaining the product codes, but as yet, now in 1995, the second
    issue has not been resolved by Committee members. Two of the later
    FSC documents submitted to the Committee had indeed allocated an
    additional byte for the product code, but had elected to reuse the
    existing product code byte as the 'lower' half of the new product
    code, which would cause existing products to be incorrectly 
    identified by existing FTS-0001 compatible FidoNet implementations.
    The behaviour of this incorrect identification has an undefined
    effect. Both proposals were rejected by the Committee on that
    basis.

    FidoNet product codes are used in the following circumstances:

     a) by mailers during FTS-0001 sessions; session negotiation is
        the exchange of FTS-0001 packet headers,
     b) by products which create type-2 packets,
     c) by mailers during negotiation of FTS-0006 (YooHoo) and 
        FSC-0056 (EMSI) sessions.

    FTS-0006 sessions allocate 16-bits for a product code, and
    FSC-0056 places no specific limits on size (although a 16-bit or
    32-bit limitation might be implied and used in implementations).
    The conclusion from this is that FidoNet product codes are still
    useful to FidoNet mailers during session negotiation using FidoNet
    enhanced handshaking protocols. Therefore, product codes are now
    being issued only for mailer products with FTS-0006 and/or
    FSC-0056 capability.

    FidoNet products without an allocated product code which either
    create type-2 packets, or negotiate FTS-0001 sessions must use a
    product code x'fe or 254 in type-2 compatible packet headers. This
    code as been reserved for that purpose (use by product without a
    product code). The product code x'ff or 255 has been reserved to
    indicate that the product code is stored elsewhere in the packet
    header at an as yet unallocated offset (please do not use this as
    yet - this FSC will be modified accordingly when FTS-0001 is
    updated to designate the correct offset).