<br><font size=2 face="sans-serif">Greetings</font>
<br>
<br><font size=2 face="sans-serif">Let me weigh in on this one. Any
attempt to "dissallow" alternatives will be ignored. This
is true because CCSDS recommendations are just that, recommendations, and
not requirements.</font>
<br>
<br><font size=2 face="sans-serif">Don</font>
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<td width=40%><font size=1 face="sans-serif"><b>"James L. Rash"
<James.L.Rash@nasa.gov></b> </font>
<br><font size=1 face="sans-serif">Sent by: sis-csi-bounces@mailman.ccsds.org</font>
<p><font size=1 face="sans-serif">04/20/2006 12:23 PM</font>
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<div align=right><font size=1 face="sans-serif">To</font></div>
<td valign=top><font size=1 face="sans-serif">sis-csi@mailman.ccsds.org</font>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
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<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td valign=top><font size=1 face="sans-serif">Re: [Sis-csi] Green book
thoughts</font></table>
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<br><font size=3>At 8:05 AM -0700 4/20/06, Scott Burleigh wrote:</font>
<br><font size=3>James L. Rash wrote:</font>
<br><font size=3>Re: [Sis-csi] Green book thoughts</font>
<br><font size=3>At 6:06 PM -0700 4/19/06, Scott Burleigh wrote:</font>
<br><a href=mailto:Lee.Neitzel@EmersonProcess.com><font size=3 color=blue><u>Lee.Neitzel@EmersonProcess.com</u></font></a><font size=3>
wrote:</font>
<br><font size=3>RE: [Sis-csi] Green book thoughts</font>
<br><font size=3 color=#000080 face="Arial">As you know, there are significant
fixed and variable costs associated with design, implementation, testing,
and deployment of each layer protocol.</font>
<br><font size=3>In my mind, this is the key point in this discussion.</font>
<br><font size=3>....</font>
<br><font size=3>So in this architecture document I think we want *not*
to encourage every flight software manager to look at each mission as yet
another opportunity to demonstrate what fools the designers of TCP were.
The architecture needs to support the insertion of alternatives to
TCP where they are needed, but the fewer the better. Suppose we leave
it at that?</font>
<br><font size=3>Scott,</font>
<br>
<br><font size=3>If I understand what you have been saying, it boils down
to the following. We as architects should aim towards saving the
mission community from making costly and/or dumb choices about rolling
their own re-transmission protocols. We should accomplish this by
(a) developing/adopting a small set of re-transmission protocols that will
meet all-but-the-most-usual-mission-needs for the future and (b) disallow
future missions from using any other re-transmission protocols over the
infrastructure we are "architecting"<b>.</b></font>
<br>
<br><font size=3>My apologies if I have misinterpreted your thesis, and
I am happy to be corrected.</font>
<br><font size=3>As Adrian points out, "disallow" isn't quite
the right word here. "Discourage" is better, and more specifically
I would say "discourage" in the sense of providing such stable
and effective functionality in the supported protocols that missions don't
have any sound technical reason to *want* to invent their own. People
will always make poor technical decisions for arguably irrational reasons;
it's not the function of the Space Communications Architecture to prevent
that. The best we can do is address in advance any arguments that
would otherwise have a defensible technical basis.</font>
<br>
<br><font size=3>Scott,</font>
<br>
<br><font size=3>Thanks -- makes sense. It also implies a means for
measuring success: the ratio of the number of missions that adopt the preferred
protocols to the number of missions that don't. But success will
be more likely if mission designers actually have enough relevant information
on which to base decisions. We can provide such information for decision-making
and produce something far more valuable and effective than a bare list
of recommendations.</font>
<br><font size=3><tt>-- <br>
</tt></font>
<br><font size=3><br>
James L. Rash<br>
Building 23, Room E403</font>
<br><font size=3>Code 588 -- Advanced Architectures and Automation Branch</font>
<br><font size=3>NASA Goddard Space Flight Center<br>
Greenbelt, MD 20771<br>
301-286-5246 (voice) 301-286-1768 (fax)</font><font size=2><tt>_______________________________________________<br>
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