Re: [Starlink] space packet protocol document

[Alexandre Petrescu <alexandre.petrescu@gmail.com>]

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The CCSDS spec is an interesting document.

I am trying to find a packet dump of a CCSDS packet that travelled in 
space according to this CCSDS spec.  If there is a place with CCSDS 
packet dumps I am interested to see them.

Given that, I could think about writing an IPv6-over-CCSDS preliminary 
Internet Draft.

I could find a png image of a packet dump at ESA 
(https://essr.esa.int/project/ccsds-wireshark-dissector), but that is 
not a real packet dump binary file that could be loaded in wireshark; 
strangely, they do provide a dissector, but not a packet.

Here are my IPv6 comments about CCSDS, relative to that png of a CCSDS 
packet (png attached):

> - the shown 'Frame Length' field is on 16bits.  For IPv6, this can be 
> fine, in principle. The good thing is that the minimum MTU of IPv6 is 
> 1280, and that can be encoded ok with a 16bit length field.  On 
> another hand, the 'Payload Length' of IPv6 is also on 16bit.  This 
> means that the largest normal IPv6 packet would not fit into a single 
> CCSDS frame, and would need to be fragmented by CCSDS.  Maybe 
> fragmentation is little desirable when RTT is 45minutes.  And, there 
> are also the IPv6 'jumbograms'.
>
> - there is a 'Spacecraft ID' and 'VC ID' fields combined on 16bits: 
> this field could be used, if appropriate in some context, to help with 
> forming IPv6 link-local addresses.  If there is worry about privacy, 
> and these IDs could be used to input hashes, such as to obtain 
> hopefully unique numbers; these hopefully unique numbers are often 
> necessary when designing IPv6 addressing architectures, subnet 
> numbers, IPv6 ULA addresses, secure addresses for secure 
> identification, and similar.
>
> - there is a 'SDLS Header' containing a 'Security Parameter Index' 
> field.  If this packet contains an IPv6 packet with an ESP header 
> (encapsulated sec'y protocol) then that too has a 'Security Parameter 
> Index' field (SPI).  It would be good to re-use.  Ideally, one would 
> rely entirely on IPsec and almost not at all on CCSDS-specific security.

Alex

Le 23/02/2024 à 19:03, Dave Taht via Starlink a écrit :
> Given the trouble the moon lander has had communicating, I looked over
> this just now.
>
> https://public.ccsds.org/Pubs/133x0b2e1.pdf
>
> I reviewed a similar document for the earth-moon corridor by NASA
> about 2 years ago, and it was a mess of non-interoperable bands and
> protocols. I cannot remember the name of that one.
>

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