[Sis-csi] RE: networking details

[Lloyd Wood]

At Thursday 08/02/2007 16:21 -0800, Scott Burleigh wrote:
>>"Operationally more expensive" would be accurate. See
>>
>>K. Hogie, E. Criscuolo and R. Parise, Putting more Internet nodes in space, CSC World, Computer Sciences Corporation, pp. 21-23, April/June 2006.
>>K. Hogie, E. Criscuolo and R. Parise, Using standard Internet Protocols and applications in space, Computer Networks, special issue on Interplanetary Internet, vol. 47 no. 5, pp. 603-650, April 2005.
>>
>><ftp://ftp-eng.cisco.com/lwood/cleo/hogie-papers/README.html>ftp://ftp-eng.cisco.com/lwood/cleo/hogie-papers/README.html
>>
>>L.
>Thanks, Lloyd.  I was actually hoping for a study that demonstrated the specific, quantitative performance inferiority of, say, AOS as compared to frame relay/HDLC -- in terms of measured throughput, undetected bit errors, etc. over some interval of operation.  Or, alternatively, a detailed cost breakdown of the expense of engineering, procuring, and operating the communication systems on two spacecraft that exercise the same applications and have comparable traffic loads but that use different link-layer and physical-layer protocols -- again, AOS vs frame relay/HDLC.

But you can carry HDLC over AOS and other CCSDS protocols using the bitstream services - the point being that doing that gives you the layering separation of modem-to-other devices, meaning you don't have to change all your installed base or reengineer as much if the modem has to change at a later pooint to support a different physical coding, while still using CCSDS links. You have less integration, and less expensive reengineering of infrastructure, without worrying about how IP packets map to CCSDS frames map to specific codings or reengineering it as the coding choices change. (Then CCSDS is used in the same way as any modem and channel coding - to do the coding alone.)

As for detailed cost breakdowns: "But we are all busy people, Assi.  Considering an issue honestly and thoroughly takes time and money, neither of which are ample for our purposes.". Money spent on such a study to "prove" what a large number of missions have demonstrated in practice is likely better spent elsewhere; I'd be very surprised if you find such a specific study done.

cheers,

L.

>  I thought that was the sort of thing Assi was talking about when he spoke of CCSDS link protocols not being very conducive to IP in space, and I'm not spotting these kinds of numbers in either of the papers you point to.  But I may have misunderstood Assi's point, and in any case these papers are a good place to start.
>
>Scott
>
>_______________________________________________
>Sis-CSI mailing list
>Sis-CSI at mailman.ccsds.org
>http://mailman.ccsds.org/cgi-bin/mailman/listinfo/sis-csi