[Sis-mia] Questions on Video Streaming Green Book

[Burleigh, Scott C (312B)]

Keith, a couple more thoughts on these questions:

On 5.4: as you say, we probably don’t want to get into this topic in this Green Book, but I think I would say that simplex links at the layer underlying the convergence layer (like the LTP link service layer) are probably no problem for the IMC spanning tree, so long as every node is able to both send and receive at the convergence layer somehow or other.  They might even be okay at the convergence layer itself, so long as the node can both send and receive bundles, though I’m less confident there.  But I can’t think of any way that a node that is truly simplex can participate in IMC.

On 6.1: I think Leigh did a lot of stress-testing LTP at 5% BER but I can’t recall whether or not he ever got any results at 10% BER.  On paper it ought to work: you lose an awful lot of segments, but if you set maxber high enough, you keep on retransmitting checkpoints and reports until eventually everything gets through.  Carlo Caini did some testing at 40% packet loss rate, which worked, so I think some optimism makes sense.  You get a pretty low throughput rate, though.

Scott

From: SIS-MIA [mailto:sis-mia-bounces at mailman.ccsds.org] On Behalf Of Scott, Keith L.
Sent: Monday, December 12, 2016 9:49 AM
To: Grubbs, Rodney P. (MSFC-EO50) <rodney.grubbs at nasa.gov>; Jeremy.Mayer at dlr.de
Cc: sis-mia at mailman.ccsds.org
Subject: [Sis-mia] Questions on Video Streaming Green Book

Hey,

Attached are some light edits and some questions about the Bundle Streaming Requirements Green Book (the comments in the markup).  Since CESG review is the only thing the Green Book goes through, can I get your feedback on the commented items before I submit to CESG?

Summary of questions:
5.2: The DLR transparent gateway – encapsulates UDP datagrams and is otherwise agnostic to the video protocol running over UDP, yes?
5.2.1: the comment in the second paragraph – is the addition correct or is it the gateway timestamp that’s being used (or something else)?
5.2.2: where you say that MPEG-TS and BP are doing some of the same things (robustness for error-recovery and interleaving) – can you say a bit more on the implications of that?
5.2.2: BP does interleaving?  I’m thinking ‘traditional’ interleaving where data items are assigned to a matrix row-by-row and read out column-by-column once the matrix is full.  I think you’re thinking of something else – can you tell me what it is you mean?
5.4: probably a question for later.
6.1: 10% BER w/ what I assume is LTP red – how does that EVER succeed?  Chances of getting 100 Bytes through correctly at 10% BER are really low.


                                --keith

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