[Sis-csi] IP Header Compression

[Greg Kazz]

Another option is to use the CCSDS Encapsulation Packet, instead of the 
CCSDS Space packet, whose header length options are currently defined as:

a) 1 byte header - used as a fill packet only
b) 2 byte header - packets up to 256 bytes in length (probably enough for 
Emergency mode type info)
c) 3 byte header - packets up to 65K bytes
d) 5 byte header - jumbo grams

There is a pink sheet out that proposed modifying the header a bit, which 
would make the header fall on a 32-bit boundary, so that those numbers 
would change to:

c) 4 byte header
d) 8 byte header

Greg

At 10:18 AM 9/1/2005, Scott,Keith L. wrote:
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>Yes, we need to look at this.  'Standard' (vj) header compression relies 
>on getting a first full-size header through, then compressing the rest 
>(not so good for the emergency command scenario).
>
>Scps-np would be a good alternative, with managed path identifiers for 
>emergencies being just 1-2 byes.
>
>   --keith
>
>
>-----Original Message-----
>From: sis-csi-bounces at mailman.ccsds.org <sis-csi-bounces at mailman.ccsds.org>
>To: sis-csi at mailman.ccsds.org <sis-csi at mailman.ccsds.org>
>Sent: Thu Sep 01 13:10:34 2005
>Subject: [Sis-csi] IP Header Compression
>
>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
>
>
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