[Sls-slp] Prox-1 GB Text for Inclusion

Tim Ray tim.ray at nasa.gov
Thu Nov 16 18:04:24 UTC 2006


Ok.  Yes, the frame-selection logic in the Blue Book looks fine.
(My original concern was based on the mistaken assumption that MAC frames
did not count as User frames)


-----Original Message-----
From: Greg Kazz [mailto:greg.j.kazz at jpl.nasa.gov] 
Sent: Thursday, November 16, 2006 11:57 AM
To: Tim Ray
Cc: sls-slp at mailman.ccsds.org
Subject: RE: [Sls-slp] Prox-1 GB Text for Inclusion


You are correct.

You have a default case where the user has no data to send just directives 
or P-frames

But I left out PLCW/Status Report  in the original GB text that mimics the 
actual frame selection rules in the prox-1 data link blue book.

The GB text should read:

.        Select a frame from the MAC Queue
.        Select a PLCW or status report if a User_frame was selected last
.        Select an Expedited Frame
.        Select a Sequenced Controlled Frame from first the Sent Queue else 
from the sequence controlled queue[1]
.        Select a PLCW or status report  if a PLCW was selected last

[1] User_frames are sequence controlled frames either from the Sent Queue 
or the Sequence Controlled Queue

So the sender should always be able to send a status report if a PLCW could 
not be sent.

But please take a look at p 4-2 (Section in the current Prox-1 
data link BB to make sure you agree with the official frame selection rule 



At 06:55 AM 11/16/2006, you wrote:

>Perhaps I am missing something, but the phrase "Select a PLCW if a PLCW was
>selected last" raised a red flag for me.  Should it be something like
>"Select a PLCW if there are no frames ready" instead?
>Consider the situation where a non-User Frame is output and then there are
>no more Frames to send.  It will never be possible to send a PLCW
>unless/until a User Frame is sent!  (You can only send a PLCW if the
>previous choice was a PLCW or a User Frame)
>-----Original Message-----
>From: sls-slp-bounces at mailman.ccsds.org
>[mailto:sls-slp-bounces at mailman.ccsds.org] On Behalf Of Greg Kazz
>Sent: Wednesday, November 15, 2006 3:49 PM
>To: sls-slp at mailman.ccsds.org
>Subject: [Sls-slp] Prox-1 GB Text for Inclusion
>Dear SLS-SLPers,
>Please review the attached text concerning the Prox-1 Frame Selection Rules
>and let me know if you have any comments concerning it. I would like to add
>this text to the Prox-1 GB to clarify the frame selection rules.
>Greg Kazz
>Chairman SLS-SLP WG
>Sls-slp mailing list
>Sls-slp at mailman.ccsds.org

More information about the SLS-SLP mailing list