[CESG] SLS Area Dispositions for SEA Condition on CESG Polls CESG-P-2016-06-001 & CESG-P-2016-05-004

Moury Gilles Gilles.Moury at cnes.fr
Tue Aug 2 08:17:04 UTC 2016

Dear Peter,
Let me answer to your mail with a few remarks :

-          First, thank you for the review of the USLP draft red book you have performed. It is very valuable and has been greatly appreciated.

-          A few statistics : you have issued 40 comments : 24 have been accepted or accepted with modification; 16 have been rejected

-          For the 16 comments rejected, the main reasons are:

o   Avoid development of a Unified COP replacing COP-1and CPO-P: we (Gian-Paolo and I) think this development, also it is a mere unification, would imply a significant amount of resources and would require a project of its own. If we include this in USLP, there is a risk that it might derail the project (i.e. significant additional delay). Therefore, we rejected your related comments;

o   Maintain compatibility with existing C&S recommendations (TC and TM) including on-going revisions (TC : addition of LDPCC; TM: addition of slicing) : USLP is a complex data link protocol unifying features we had in TC, TM and/or AOS, and adding new features to cover emerging user needs. Nevertheless, we should maintain compatibility/coherency between the CCSDS recommendations at the various layers. It does not mean we want to stifle innovation but we want, while innovating at the various layers, to avoid introducing incompatibilities /incoherencies that would be detrimental to CCSDS credibility as an organization developing communication standards following an OSI layered architecture. So the innovations at the various layers need to be somehow coordinated so that the interfaces still interoperate when one layer is updated;

o   Keep stable book structure for CCSDS data link protocol recommendations (true also for C&S), unless of course errors, flaws and incompatibilities with new features to be introduced are discovered. This is why we have rejected a number of your comments asking for changing either document structure, ordering of subsection/requirements or altering standard text found in existing CCSDS data link protocol books. The rationale for change you propose is usually valid. Some of your proposed changes have been accepted because they clearly correspond to errors that need to be corrected. The rest have been rejected because: either the rationale was false, or we did not think the improvement was significant enough to justify a change.

-          In any case, this USLP red book will probably go through several agency reviews before it is finalized. Therefore, there will be opportunities to input any comment/RID that you think need to be discussed and dispositioned by the WG.

-          As a conclusion and in response to the general tone of your mail, I would say that SLS AD & DAD are not trying to stifle innovation but rather to maintain coherency of the CCSDS stack of protocols (especially those under their responsibility), while constantly innovating at the various layers.

Best regards,


Gilles MOURY
CNES Toulouse
De : CESG [mailto:cesg-bounces at mailman.ccsds.org] De la part de Shames, Peter M (312B)
Envoyé : mercredi 27 juillet 2016 19:47
À : Gian.Paolo.Calzolari at esa.int; CCSDS CESG --
Cc : Tom Gannett; Massimo.Bertinelli at esa.int; Kazz, Greg J (312B)
Objet : Re: [CESG] SLS Area Dispositions for SEA Condition on CESG Polls CESG-P-2016-06-001 & CESG-P-2016-05-004

Gippo, Gilles, et al,

In the interest of moving these documents into agency review I am going to accept the current resolution of conditions and agree to sending these out to the agencies.

That said, I do want to go on the record that I am concerned that what appears to be a very strict adherence to a policy of “we can’t change that, it’s in older documents” is a sure fire way to stifle creativity and forward progress.  If the Internet took that approach we would not have IP v6, nor the van Jacobsen performance mods to TCP, nor SMTP with MIME types, nor HTTPS and HTML5, nor … The same sort of progression can be seen in Ethernet evolution (was 1 Mbps, now over 1 Gbps), for USB (was 1.1 Mbps, now on version 3 and 480 Mbps).  There is a very long list of improvements that other standards organizations have been able to make that have moved them ahead in performance and features.  But we seem to be getting continual push back that things can’t evolve, nor descriptions be clarified, because of some choices made 15 (or more) years ago.

I will point out that if we had used this same approach 15 years ago when those SLP docs had a major revision that we never would have had the improved SLP protocols docs we now have; we would have stuck with the original versions from the 1980’s.  I do believe that we must be careful about what we change, so as to preserve backward compatibility and not break existing infrastructure (see Architecture Principles, “A4 MINIMIZE DISRUPTIONS Statement: Minimize Disruptions to Existing Standards and Installed Systems”).  But note that this does not say “don’t change anything”.  It does say “… there will also be situations where unforecasted mission requirements or operating modes will mandate consideration of otherwise disruptive approaches.”

When we are developing major new capabilities, such as USLP surely represents, we should be more bold just because we are defining something that is explicitly intended to move us into the future.  And, because this is nowhere implemented, just because it is brand new, we should have no fear of breaking anything because there is no existing infrastructure that supports this protocol nor the data rates it is capable of sustaining.

Regards, Peter

From: CESG <cesg-bounces at mailman.ccsds.org<mailto:cesg-bounces at mailman.ccsds.org>> on behalf of Gian Paolo Calzolari <Gian.Paolo.Calzolari at esa.int<mailto:Gian.Paolo.Calzolari at esa.int>>
Date: Wednesday, July 27, 2016 at 3:37 AM
To: CCSDS Engineering Steering Group - CESG Exec <cesg at mailman.ccsds.org<mailto:cesg at mailman.ccsds.org>>
Cc: Tom Gannett <thomas.gannett at tgannett.net<mailto:thomas.gannett at tgannett.net>>, "Massimo.Bertinelli at esa.int<mailto:Massimo.Bertinelli at esa.int>" <Massimo.Bertinelli at esa.int<mailto:Massimo.Bertinelli at esa.int>>, Greg Kazz <greg.j.kazz at jpl.nasa.gov<mailto:greg.j.kazz at jpl.nasa.gov>>
Subject: [CESG] SLS Area Dispositions for SEA Condition on CESG Polls CESG-P-2016-06-001 & CESG-P-2016-05-004

Dear Peter,
        please find in the attached file the SLS Area Dispositions for SEA Condition on CESG Poll CESG-P-2016-06-001.

The SLS  Area Dispositions for SEA Condition on CESG Poll  CESG-P-2016-05-004 are already available as per https://mailman.ccsds.org/pipermail/cesg/2016-July/000991.html .

All SLS Area dispositions have been coordinated with the relevant WG Chairs.

SLS Area AD and DAD are confident we can proceed for both CMC Polls with acceptance of the dispositions by SEA Area as soon as the  CCSDS Editors implements the agreed changes.

Best regards

Gian Paolo & Gilles

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