[Sis-csi] IP Header Compression

[Keith Hogie]

Chris,

  I agree we need to consider issues with small packets and low rates, 
but how low do we need to go.  In all of the missions I have seen (non 
deep space), the lowest data rates are 125 bps.  This is over an order 
of magnitude difference from your 10 bps. 

  For the Cislunar environment, we need to figure out what some of our 
limits are.  Do we really want to burden the Cislunar design with issues 
that only relate to Deep Space?

  Also, for hardware decode commands like hardware reset, I'm not sure 
if packet sizes or IP or CCSDS headers really matter.  Isn't a hardware 
decode command just a string of bits (hopefully long enough to be 
unique) that get grabbed by hardware without any special packet 
knowledge.  That would mean that this bit string can be carried inside 
any packet and the only length that matters is the length of the 
hardware command bitstring.

Keith Hogie

Krupiarz, Christopher wrote:

> I was curious about thoughts as to if and where we would address IP 
> header compression in the Green Book.  On some our missions (and I 
> think this is typical at least in deep space), if we have a reset of 
> the system, the spacecraft may come up in an emergency mode of 
> receiving 10 bps.  Hence, every bit is quite valuable at this point.  
> With a CCSDS header, we're looking at 6 bytes (plus a couple of bytes 
> if a secondary header is used).  If we move to IPv6, this becomes 40.  
> At 10 bps, that's an additional uplink time of 25-26 seconds before a 
> command can be received which is long enough to envision some 
> nightmare scenarios.  Clearly IP header compression would alleviate 
> this concern but I'm not sure where it fits or if it is needed in this 
> doc (I hope I didn't miss it somewhere).
>
> Chris
>
>------------------------------------------------------------------------
>
>_______________________________________________
>Sis-CSI mailing list
>Sis-CSI at mailman.ccsds.org
>http://mailman.ccsds.org/cgi-bin/mailman/listinfo/sis-csi 
>  
>
----------------------------------------------------------------------
  Keith Hogie                   e-mail: Keith.Hogie at gsfc.nasa.gov
  Computer Sciences Corp.       office: 301-794-2999  fax: 301-794-9480
  7700 Hubble Dr.
  Lanham-Seabrook, MD 20706  USA        301-286-3203 @ NASA/Goddard
---------------------------------------------------------------------- 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ccsds.org/pipermail/sis-csi/attachments/20050906/2ddbc5cc/attachment.html