[Sls-slp] JAXA RID against OID Frame
edward.greenberg at jpl.nasa.gov
Wed Mar 4 11:02:54 UTC 2009
I agree with Matt and Gian Paolo. If you want to send a packet with a meaningful secondary header and no useful information thengive it an APID with that interpretation, not one that says it only contains idle data. Have a wonderful time discussing this trivia.
On 3/4/09 1:59 AM, "Cosby Matthew" <MCOSBY at qinetiq.com> wrote:
I agree with Gian Paolo.
When our TM systems detect an Idle Packet (APID set to 0x7FF) it discards it.
>From the TM Spec.
220.127.116.11 Extracted Packets shall be delivered to the users on the basis of the PVN in their header. Incomplete Packets are not required to be delivered in cross support situations.
NOTE . Idle Packets are discarded. Data Fields that contain only Idle Data are also discarded.
This states that the Idle Packet is discarded and implies that there is no user data within the packet. There probability isn't any where in the standard stating that you can't put a secondary header in the Idle Packet, but this is implied as this packet is thrown out. So quoting Gian Paolo it would be crazy to put any useful data into the idle packet.
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From: sls-slp-bounces at mailman.ccsds.org [mailto:sls-slp-bounces at mailman.ccsds.org] On Behalf Of Gian.Paolo.Calzolari at esa.int
Sent: 03 March 2009 18:21
To: Kazz, Greg J
Cc: sls-slp at mailman.ccsds.org; Takahiro Yamada; Ray,Timothy J. (GSFC-583.0); Jean-Luc.Gerner at esa.int; sls-slp-bounces at mailman.ccsds.org; gilles.moury at cnes.fr; Greenberg,Edward
Subject: RE: [Sls-slp] JAXA RID against OID Frame
"Kazz, Greg J" <greg.j.kazz at jpl.nasa.gov> wrote on 03-03-2009 18:21:35:
> But a Space Packet can contain a Secondary Header, which could
> contain useful data as well. So in that sense, OID Packet also makes
> sense. In other words, discarding an "Idle Packet" can have a
> drawback or unintended consequence. CCSDS needs to use consistent
> terminology across the board and I think that is what this JAXA rid
> is pointing out. I am looking forward to Marjorie's responses to
> those rids as well.
The Frame has a structure linked to the Virtual Channel and all frames on a VC have the secondary header (if this is used) independently they are OID or not.
Conversely the Space Packet has a structure linked to the APID and a mission implementing a Packet Secondary Header on Idle Packets would just be crazy. :-) In addition, I think that, being the idle APID fixed, there is no chance for having a Secondary header in an Idle Packet [this is TBC].
Comments/confirmations are welcome.
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