[Sls-slp] Does SDLS apply to USLP truncated transfer frame ?

Moury Gilles Gilles.Moury at cnes.fr
Tue Oct 27 11:13:21 UTC 2020

Dear Greg,

Sorry for not being able to join the SLP meeting yesterday but I had another meeting at the same time that lasted more than scheduled.

For the issue you raised concerning the applicability of SDLS to truncated USLP frames, I will add it to the discussion of the SDLS WG on Wednesday. My feeling is that, also security would be needed on those emergency commands, the fact that minimum length for Security Header is something like 6 octets (TC baseline mode for SDLS) and minimum length for Security Trailer is something like 16 octets (TC baseline mode for SDLS) would make it :

-          impossible to fit a truncated USLP Transfer Frame into a 7 octets BCH codeblock (truncated USLP Transfer Frame header is 5 octets leaving only 2 octets for data field)

-          only possible to fit a truncated USLP Transfer Frame into a 32 octets LDPC codeblock (leaving only 27 octets for data field – 22 octets being taken by Security and Trailer)
We will discuss it further with the SDLS WG. I do not know whether shorter Security Header and Trailer can be envisioned for those emergency commands carried in truncated USLP Transfer Frames.

See you (virtually) this afternoon for the SLP webmeeting. I will provide input for the TM and AOS pink sheets regarding MCID/VCID validation in order to align TM/AOS with TC/USLP regarding this validation.

Best regards,


Gilles MOURY
CNES Toulouse
De : Kazz, Greg J (US 312B) <greg.j.kazz at jpl.nasa.gov>
Envoyé : lundi 26 octobre 2020 18:45
À : Moury Gilles <Gilles.Moury at cnes.fr>; sls-sdls at mailman.ccsds.org
Cc : Kazz, Greg J (US 312B) via SLS-SLP <sls-slp at mailman.ccsds.org>
Objet : Does SDLS apply to USLP truncated transfer frame ?

Dear Gilles and SLDS WG,

SLP WG has a question regarding the application of the SDLS protocol to truncated USLP Transfer Frames.
These truncated frames are envisioned for very short length telecommands or forward link Proximity-1 link commanding. This frame type provides backward compatibility with TC hardware commands or immediate commands. These commands are typically 2 octets long. We envision the truncated USLP frame length to be between 8 and 32 octets.
In that context, does it make sense for SDLS header and possibly SDLS trailer to apply to the USLP truncated frame.

The discussion of the proposed non-use of SDLS for truncated USLP frames is mentioned in Chapter 6, specifically  in Section 6.3.2. The definition of the truncated USLP frame is in Annex G of the attached draft document

The SLP WG did not think SDLS should be applicable to truncated USLP frames, but we would like your opinion on this matter.

Best regards,
Greg Kazz
Chair SLP WG

From: SLS-SLP <sls-slp-bounces at mailman.ccsds.org<mailto:sls-slp-bounces at mailman.ccsds.org>> on behalf of Matthew Cosby <Matt.Cosby at Goonhilly.org<mailto:Matt.Cosby at Goonhilly.org>>
Date: Monday, October 26, 2020 at 9:27 AM
To: "sls-slp at mailman.ccsds.org<mailto:sls-slp at mailman.ccsds.org>" <sls-slp at mailman.ccsds.org<mailto:sls-slp at mailman.ccsds.org>>
Subject: [EXTERNAL] [Sls-slp] Updated Book


Here is the updated book from the working group today.

Regards, Matt.

Matthew Cosby
Chief Technology Officer
Goonhilly Earth Station Ltd
[cid:image001.jpg at 01D6AC56.134A7520]

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