Re: [nwcrg] [dtn] Network Coding and SATCOM - call for review

"Kerim Fouli" <fouli@codeontechnologies.com> Fri, 16 November 2018 20:18 UTC

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From: Kerim Fouli <fouli@codeontechnologies.com>
To: 'Lloyd Wood' <lloyd.wood@yahoo.co.uk>, 'Kuhn Nicolas' <Nicolas.Kuhn@cnes.fr>, Tomaso.deCola@dlr.de
Cc: vincent.roca@inria.fr, marie@mjmontpetit.com, nwcrg@irtf.org
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Date: Fri, 16 Nov 2018 15:17:50 -0500
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Subject: Re: [nwcrg] [dtn] Network Coding and SATCOM - call for review
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Hi Lloyd,

Thank you for the interesting point on Sat links and network coding. Coding
and PEPs are certainly not mutually exclusive, and coding has a lot to offer
on the caching side that is not represented in the article either.

However, there may still be other gains purely at the link level: The
attached white paper illustrates that a network-layer code can allow the PHY
code to let through more errors, leading to link budget gains.  

Best,

Kerim



-----Original Message-----
From: nwcrg <nwcrg-bounces@irtf.org> On Behalf Of Lloyd Wood
Sent: Tuesday, November 13, 2018 9:35 PM
To: Kuhn Nicolas <Nicolas.Kuhn@cnes.fr>; Tomaso.deCola@dlr.de
Cc: vincent.roca@inria.fr; marie@mjmontpetit.com; nwcrg@irtf.org
Subject: Re: [nwcrg] [dtn] Network Coding and SATCOM - call for review

Likely relevant to this draft:


Can network coding bridge the digital divide in the Pacific?, Spiedel et
al., International Symposium on Network Coding (NetCod), Sydney, June 2015.


http://arxiv.org/abs/1506.01048
http://dx.doi.org/10.1109/NETCOD.2015.7176795
https://internetnz.nz/sites/default/files/IR201404%20-%20University%20of%20A
uckland%20-%20FINAL%20REPORT%20April%202015.pdf
https://conference.apnic.net/data/41/apricot-talk_1451964216_1456023873.pdf

My take from years of using a very large number of TCP accelerators across
satellite links is that:

- the performance benefits from the local file/stream/chunk/'object' rapid
fetch
  from Internet side and cached delivery that they offer for the satellite
link
  will far outweigh benefits of network coding across the path and its
virtual
  'erasure channel' for responsiveness, but that's hard to see from a
throughput
  graph.


- the over-satellite-link FEC feature offered is rarely that useful in
practice,
  as channel coding makes it largely redundant. If the PEP accelerator FEC
becomes

  useful, the channel coding needs to be adjusted for the SNR, and that's
often

  a local ACM problem, e.g. heavy rain fade at Ka-band, which the O3b
example used
  in the paper suffers from.

- there's a whole bunch of tuning of traffic for the offered satellite link
  capacity (QoS, prioritisation, shaping, etc) brought to the table by PEPs
  that network coding cannot consider. Sometimes this gets called
'Orchestration',
  though that means different things to different communities.


oh, draft typo: writting->writing. Haven't had the time to reread and think
about the whole draft revision yet.

L.
 
Lloyd Wood lloyd.wood@yahoo.co.uk http://about.me/lloydwood



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