Re: [nwcrg] [LOOPS] BOF co-chairs thinking on LOOPS next steps

[Emmanuel Lochin <[e-mail]>]

Hi Spencer, all,

On 30/07/2019 16:22, Spencer Dawkins at IETF wrote:
>
>  1. How a sender tunes FEC dynamically - is that automatic, based on
>     FEC mechanisms people are thinking about, or is there work to do
>     there?
>  2. How a sender knows whether to do FEC, retransmission, or both FEC
>     and retransmission, dynamically?
>  3. How a sender knows that it shouldn't be doing anything, because
>     anything it does won't help ("first, do no harm")?
>
IMHO, each answer depends on which layer you seek to apply FEC and why. 
Adding and adapting FEC at L2 or L3 does not have the same impact than 
at L4 and does not lead to the same adaptive mechanism. Then, adding FEC 
at L4 also depends on whether you are congestion controlled or not, you 
want to stick to TCP-friendliness, your QoS objectives, and many other 
things...
Finally concerning #3, I would say that monitoring the e2e delay would 
give you a good indication to enable FEC or not. If the delay is 
"small", you won't beat ARQ.

Emmanuel


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Emmanuel LOCHIN
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