Re: rfc983


Marshall Rose (mrose@nrtc-gremlin)
Thu, 12 Jun 86 14:03:57 -0700


    As one of the authors of the RFC, I feel I should clear up some
    misconceptions you have regarding it.

    At no point in rfc983 is it said how to implement the interface to
    the TSAP. What is said is how you can build such an interface on
    top of the TCP. That is, given the abstract service definitions for
    the TP, instructions are given as to how one can map those onto the
    services provided by the TCP. From our perspective, a proper
    implementation of rfc983 exhibits the following properties:

        - it has the TSAP interface that you want on your host
        - it uses the protocol defined in the rfc

    We have such an implementation for Berkeley 4.2 UNIX. I imagine
    that an implementation for TOPS-20 would look entirely different,
    both in actual internal code (the protocol engine) and in the
    interface code (subroutine library). The same goes for VAX/VMS,
    obviously. But, they would all speak the same protocol (as defined
    in rfc983).

    Perhaps the problem here, is that it appears to you that rfc983
    specifies an "ISO protocol". This is certainly not our intention.
    the rfc specifies a DDN-style protocol which provides ISO
    services. It is the intent of rfc983 to permit standard ISO
    protocols to run on top of the TCP. It is not the intent to build
    ISO-like protocols for the ARPA Internet.

    I completely agree with your statement that:

         "In general, it is important for one to produce good generic
         protocol interface design so that a particular protocol
         implementation or even the protocol itself can easily be
         replaced without affecting the code in the upper or lower
         layer."

    But I fail to see how rfc983 violates this concern. Quite the
    contrary: rfc983 rips out the ISO TP internals and substitutes
    calls to the services provided by the TCP!

/mtr



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