[Sls-slp] [Sls-sea-dls] Order of Processing between TC-SDLP, COP-1 and SDLS

Greenberg, Edward (313B) edward.greenberg at jpl.nasa.gov
Thu Apr 11 17:22:39 UTC 2013

Thanks for your input.  I am still concerned with your item 2 as copied:
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On 4/11/13 1:57 AM, "Marjorie de Lande Long" <marjorie at delandelong.com>

>2) For a system where the SDLS processing is before FOP-1 at the sending
>end and after FARM-1 at the receiving end
>2.1  In this system, a frame can be lost because of an SDLS failure
>after the frame has been acknowledged and delivered by FARM-1. This is
>similar to an error being detected when reassembling a packet from
>multiple frames.
>2.2  It is happening above COP-1, so, strictly speaking, the COP-1
>delivery assumptions are not compromised.
>- The COP-1 delivery guarantee applies only as far as the output from
>the FARM: if a frame suffers an error after that, then that is not
>COP-1's problem. (It is a problem and it needs to be reported but it is
>not COP-1's problem.)
>- An example of one of these errors is mentioned in 2.1: there are
>existing systems that handle this error.
>2.3  The SDLS failure is detected above the FARM, as the frame is being
>passed upwards.  So it does not look so convenient to try to pass
>information downwards (e.g. into the FARM) so that the SDLS Error Flag
>can be set in the CLCW.
>2.4  The failure needs to be reported - see 3.5 and 3.6 below.
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First of all the implementation of the flag is simple.  A wire from the
SDLS process that is set to a 1 when a frame is rejected and reset to a 0
when a frame is accepted is all that is needed.  This wire is sampled and
becomes the flag when the CLCW is composed.

Defining and then using a new CLCW to carry the information about the
details of an SDLS failure seems simplistic and according to the frame
processing rules would be in clear.  Identifying why an SDLS failure
incurred when no errors where caught needs more than a 32 bit diagnosis.
I would suspect that a packet of information would be more appropriate.
Even if encryption was not used for the frame the packet's content could
be encrypted. 

The rationale for the flag in the CLCW was to let the COP know that an
error occurred and its continued presents would inform the COP that
continuation of COP activities was useless.  

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