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

[Spencer Dawkins at IETF <[e-mail]>]

I'm going to be replying to two or three e-mail in this thread, so I'll try
to be coherent over my replies ...

On Tue, Jul 30, 2019 at 9:42 AM Marie-Jose Montpetit <[e-mail]>
wrote:

> Since most of your questions are related to FEC I copy the nwcrg. See
> <mjm> below
>
> mjm
>
> Marie-José Montpetit, Ph.D.
> Research Affiliate, MIT Media Laboratory
> [e-mail]
> [e-mail]
>
> On July 30, 2019 at 10:23:04 AM, Spencer Dawkins at IETF (
> [e-mail]) wrote:
>
> Hi, Mirja,
>
> On Tue, Jul 30, 2019 at 5:34 AM Mirja Kuehlewind <[e-mail]>
> wrote:
>
>> Hi Carsten, hi Spencer,
>>
>> > On 25. Jul 2019, at 20:59, Spencer Dawkins at IETF <
>> [e-mail]> wrote:
>> >
>> > My impression, and Magnus might say I'm insane, was that Magnus is
>> right on the edge of whether this work can be chartered without a second,
>> working group-forming BOF. If the LOOPS community can't live without
>> host-to-node, the community should add it. If the community can make use of
>> LOOPS without host-to-node and add it later, the community might consider
>> whether that reduces the scope of the initial proposed charter enough to
>> help Magnus approve it :-)
>>
>> Yes, it would be possible to charter without another BoF a small and
>> well-scoped group, however, it also would be possible to work on small and
>> well-defined pieces of work without a new working group. This was one of
>> the reasons why this was not a non-wg-forming BoF because it is not clear
>> yet if a new group is needed or the resulting pieces of standardization
>> work are small enough to fit into an existing group.
>>
>> Therefore, I really recommend focus on defining the standardising work
>> items that you think are needed rather than trying to do any word-smithing
>> of a potential charter (that eventually is not needed).
>>
>
> Thanks for giving me the chance to clarify - I really was talking about
> chartering work, not just chartering a working group, but that wasn't clear
> from my note. As you said, knowing what the work is, in more detail, will
> help you and Magnus know what to do next.
>
> So, my suggestion for the interested community is to nail down
>
>    1. In order to "do LOOPS", what already exists, that can be used
>    without changes?
>    2. what already exists, but needs to be extended for LOOPS?
>    3. what needs to be created, because nothing exists that meets the
>    needs?
>
>  I'm not a LOOPS proponent (the ADs asked me to chair the BOF about a
> month before IETF 105), but speaking as someone who hasn't been involved in
> depth, I wonder about
>
>    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?
>
> <mjm> There are FEC mechanisms to adapt coding dynamically based on
> acknowledgments for example. In the QUICK implementation we will have flag
> a RECOVERED packet that could be used to adapt the coding rate. Other
> implementations or code-specific protocols are also available.
>
>
>    1.
>    How a sender knows whether to do FEC, retransmission, or both FEC and
>    retransmission, dynamically?
>
> <mjm> Well the use of FEC (or not) is a design decision.  Of course you
> need the code (and the libraries). And then the decision will be based on
> known link condition, goodput, expected performance, type of traffic
> (video, time sensitive etc.). And finding a tunnel and PEPs if you need to.
> And it can depend on path statistics and not being end to end. I am not
> sure you could standardize that decision.
>

So, speaking with no dots because I don't have any, I agree with what
Marie-Jose is saying here, but my understanding is that LOOPS endpoints
might turn LOOPS off completely if local optimizations aren't needed. So
I'm thinking about how a sender makes that decision, and how a sender might
do trade-offs.

I think one point in discussions with Marie-Jose might be that she's
thinking in terms of Technical Specifications (
https://tools.ietf.org/html/rfc2026#section-3.1), which are necessary, but
discussions are making me think that proponents might usefully also think
in terms of Applicability Statements (
https://tools.ietf.org/html/rfc2026#section-3.2), which (quoting)

   An Applicability Statement specifies how, and under what
   circumstances, one or more TSs may be applied to support a particular
   Internet capability.  An AS may specify uses for TSs that are not
   Internet Standards, as discussed in Section 7.

   An AS identifies the relevant TSs and the specific way in which they
   are to be combined, and may also specify particular values or ranges
   of TS parameters or subfunctions of a TS protocol that must be
   implemented.  An AS also specifies the circumstances in which the use
   of a particular TS is required, recommended, or elective (see section
   3.3).

   An AS may describe particular methods of using a TS in a restricted
   "domain of applicability", such as Internet routers, terminal
   servers, Internet systems that interface to Ethernets, or datagram-
   based database servers.

So, if Applicability Statements (also standards-track documents) would be
helpful for LOOPS deployment and operation, the proponents might think
about whether they want to do work in that space.

If decisions about what senders do turn out to be entirely up to the
sender, that's great, but if the proponents want to bound the possible
behaviors of implementations to improve deployment and operation, that
might also be appropriate in BCPs (
https://tools.ietf.org/html/rfc2026#section-5).


>
>    1.
>    How a sender knows that it shouldn't be doing anything, because
>    anything it does won't help ("first, do no harm")?
>
> <mjm> Of course in a congested network doing nothing is probably best.
> Again there is a lot of work on the interaction of coding and congestion
> control.
>
> <mjm> Not everyone knows the things but there has been a lot of work in
> FECFRAME (in IETF) and NWCRG. Someone did mention that a lot of the work
> was done in a research group not a working group. But real implementations
> exist in famous “networks".
>
Right - so one possibility is publishing work from NWCRG in the IETF
stream, and especially standards-track, with appropriate review by the IETF
community. That could take a lot of forms (RGs and WGs can interact in a
lot of different ways).

> <mjm> Since most of your questions are about erasure coding (coding for
> packet loss) is that a direction LOOPS wants to take? Somekind of nwcWG?
>

See Mirja's note about chartering work, and only chartering working groups
when that's needed. But as you note, the FECFRAME extensions happened in
TSVWG, so that would be a reasonable conversation to have with TSVWG chairs
(and I note that Wes Eddy, who popped up further down in this thread, is a
TSVWG co-chair). If it fits, TSVWG could be a plan. If it doesn't fit in an
existing working group, NWCWG could be a plan.

>
> mjm
>
>
>
> Does everyone know how to do those three things, except me? :-)
>
> Pointers to specifications would be awesome ...
>
> Spencer
>
>
>> Mirja
>>
>>
>>
>> --
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