Re: [core] Fwd: New Version Notification for draft-gomez-core-coap-space-00.txt

[Carles Gomez Montenegro <[e-mail]>]

Hello Christian,

(Apologies for the late response... And taking the liberty of CC'ing
the deepspace ML, even if just as "FYI".)

Thanks a lot for such detailed and interesting feedback!

It is encouraging to know that there has been already discussion on
FEC for CoAP.
Indeed, in addition to existing (terrestrial) use cases, deep space
may further contribute an additional incentive to materialize related
ideas into actual proposals (I-Ds).

Cheers,

Carles


On Thu, 21 Dec 2023 at 10:38, Christian Amsüss <[e-mail]> wrote:
>
> Hello Carles,
> hello CoRE,
> (deepspace@ removed b/c this is more CoAP technical)
>
> On Wed, Dec 20, 2023 at 07:54:59AM +0100, Carles Gomez Montenegro wrote:
> > no proposal has been made to add support of Forward Error Correction
> > (FEC) to CoAP.
>
> There has been some discussion in hallway meetings and in the RIOT
> community chats on FEC for block-wise transfer (which have indeed not
> resulted in any written down proposals). This would not only be
> applicable to deep space, but also to terrestrial multicast channels
> when used for firmware updates.
>
> Discussion there was mainly focused on regular and not Q-Blocks, because
> the latter have a very tight set of constraints for their applicability,
> and because mechanisms introduced there (eg. the
> application/missing-blocks+cbor-seq type) can just as well be applied to
> regular block-wise transfer.
>
> One aspect that was discussed there was the choice of transmission
> sequence and sharding, where memory and code complexity requirements are
> traded against robustness of the protocol. Another trade-off to be
> considered is fast forwarding: For the applications that have been
> discussed previously, relaying through a proxy was highly relevant, and
> that proxy can not only terminate retransmissions, but also participate
> in FEC. If the proxy can not spool the whole resource, a wider spread of
> FEC (which is desirable for robustness) leads to the proxy being unable
> to participate in FEC. (As a complete space layperson, I imagine that
> such a proxy would be highly capable though, and could easily do all FEC
> recovery -- images of space stations receiving transmissions and
> forwarding them to ground stations once they pass over them comes to
> mind).
>
> BR
> Christian
>
> --
> To use raw power is to make yourself infinitely vulnerable to greater powers.
>   -- Bene Gesserit axiom