[Sls-slp] Re: [CESG] Draft Green Book on Space Packet Protocol

Robert C. Durst durst at mitre.org
Wed Aug 20 14:48:26 UTC 2003

> > The most fundamental question for me is "Is there really
> a Space Packet
> > Protocol" or is there just a Space Packet Construction
> Rule and a set
> > of loosely defined processes that describe things you
> might do with it?
> > In SPP-RB all that is really clearly defined are the
> packet construction
> > rules. In this document there are some functional /
> protocol views that
> > describe how you might construct entities that
> participate in the transfer
> > of these packets, and there is an abstract description
> of protocol
> > entities, but these is no solid definition of the state
> machines that
> > might exist within any of these entities nor of what
> procedures they follow.
> I think what a protocol specifies is a set of rules to be
> used by both sender and receiver to perform
> communications. I don't think all protocols must have
> state machines. For example, UDP doesn't. But both SPP and
> UDP define a set of rules to be used by both sender and
> receiver to perform communications. So I think they are
> still protocols, although they are very simple ones.

In this and the duscussion that followed (deleted here), Takahiro
is correct in his assertion that state machines are not essential to
protocol definition.  They, or something similarly unambiguous,
are convenient means of describing the operation *of stateful
protocols*, but SPP (and UDP) are essentially stateless --
there is no protocol exchange that alters the subsequent
behavior of the protocol itself.  (Documenting all the
management functions that replace the in-line protocol is a
different, and possibly stateful, issue, mut not the issue at
hand here.)

Bob Durst

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