Re: [OPSAWG] Mirja Kühlewind's No Objection on draft-ietf-opsawg-ipfix-bgp-community-11: (with COMMENT)

[Stewart Bryant <[e-mail]>]

On 30/11/2018 19:23, Spencer Dawkins at IETF wrote:
> This is Mirja's comment, but ...
>
> On Fri, Nov 30, 2018 at 10:12 AM Mirja Kühlewind <[e-mail] 
> <mailto:[e-mail]>> wrote:
>
>     Mirja Kühlewind has entered the following ballot position for
>     draft-ietf-opsawg-ipfix-bgp-community-11: No Objection
>
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>
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>
>     The document, along with other ballot positions, can be found here:
>     https://datatracker.ietf.org/doc/draft-ietf-opsawg-ipfix-bgp-community/
>
>
>
>     ----------------------------------------------------------------------
>     COMMENT:
>     ----------------------------------------------------------------------
>
>     One comment on section 1:
>     "For example, they can shift some flows
>       from congested links to low utilized links through an SDN controller
>        or PCE [RFC4655]."
>     I'm not aware that ipfix information is commonly used for dynamic
>     traffic
>     adaptation and I'm not sure that is recommendable. C
>
>
> I'm agreeing with Mirja here.
>
> We've spent a LOT of time not recommending dynamic traffic adaptation. 
> Probably half my responsibility as AD for ALTO was repeating "you 
> can't react based on changes to that attribute without taking chances 
> on oscillation" like it was a mystical incantation, and I wasn't the 
> first AD to have that conversation repeatedly.

Yes, I understand the ARPA net had exactly that problem at one stage and 
had to be converted from using a delay based metric to a fixed metric.

>
> I would be happy to hear that all those problems are solved, but I 
> haven't heard that yet. Do the right thing, of course.
>
> Even "can shift some flows from persistently congested links to 
> underutilized links" would cause me less heartburn.

There is no such thing as permanent in network paths!

Like many control problems the first order solution is to damp with a 
suitably long time constant, but  infinity, i.e. permanent, is not a 
satisfactory choice either.

- Stewart

>
> Spencer