[Sls-slp] RE: Encapsulation Service

Durst, Robert C. durst at mitre.org
Wed Apr 19 20:40:12 UTC 2006

 >>While this is probably the pragmatic approach, the 
>implication of this is 
>>that two implementors can provide the same CCSDS service in a 
>way that is 
>>not, and cannot be configured to be, interoperable.  I find this 
>>disturbing.  This possibility at least  needs to be noted, 
>and added to 
>>the list of parameters that are managed among implementors.  
>This seems 
>>like a rather serious flaw to me.  I would much rather see a 
>>to implement both and an option to use either on a per-mission 
>>basis.  Failing that, I'd like to see a Protocol Implementation 
>>Conformance Statement developed and made mandatory, so that 
>there is no 
>>ambiguity about what an implementor has implemented.
>Actually it is already a managed parameter. It's the PVN , 
>i.e., packet 
>version number in the Space Link Identifers blue book. It tells the 
>receiver how to interpret the packet, i.e., how to find the 
>length field, 
>in order to extract it and assemble it. Encapsulation Packets 
>have a unique 
>PVN, so do Space Packets and they are distinct.
>So CCSDS has provided a mechanism for space agencies to be 
>But that doesn't proclude some hypothetical rogue space agency 
>who "gets 
>there first" who only chooses to support bit streams instead of CCSDS 
>recognized packet version numbers.

OK, that covers my concern.

> >>I think that it would be useful to summarize the "managed 
> >>somewhere, to make it clear specifically what bilateral
> >agreements are
> >>required to ensure interoperability.  This may be part of the
> >>within the CCSDS community, but if we want other folks to use
> >this, making
> >>it clear what needs to be agreed upon out-of-band seems important.
>Didn't see any comment on this (but then, my comment didn't require 
>any).  Any thoughts on an annex to summarize these?
>I think we are between messages. You are probably reading that second 
>message now. Actually Yamada has already captured the managed 
>parameters in 
>Table 5-1 of the Encapsulation Packet service, but he didn' t 
>reference the 
>controlling document for each parameter and more cleanly 
>deliniate what 
>applies when one use Space packets vs Encapsulation packets.

Ah, OK. 

I believe that this fully covers my concerns.  Thanks to you, Takahiro,
and Tom.


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