On 06/12/2018 07:55, Dongjie (Jimmy) wrote:
Hi Spencer, Stewart, Joel,

Thanks for the discussion about the congestion adaptation. We agree the 
reactive congestion adaptation may need further investigation.

Thus in order to solve Mirja's comment, we plan to make that example more 
generic with something like:

"For example, the collected information could be used for traffic monitoring, and 
could optionally be used for traffic optimization according to operator's policy."

Sounds much better.

Stewart


Best regards,
Jie

-----Original Message-----
From: Joel M. Halpern [mailto:j...@joelhalpern.com]
Sent: Wednesday, December 05, 2018 12:03 AM
To: Spencer Dawkins at IETF <spencerdawkins.i...@gmail.com>; Stewart
Bryant <stewart.bry...@gmail.com>
Cc: opsawg-cha...@ietf.org; opsawg@ietf.org; Mirja Kuehlewind
<i...@kuehlewind.net>; IESG <i...@ietf.org>;
draft-ietf-opsawg-ipfix-bgp-commun...@ietf.org
Subject: Re: [OPSAWG] Mirja Kühlewind's No Objection on
draft-ietf-opsawg-ipfix-bgp-community-11: (with COMMENT)

The conclusion earlier work on congestive response routing reached was that
one needed to pin the specific routing decision until the selected path became
infeasible.

Yours,
Joel

On 12/4/18 10:59 AM, Spencer Dawkins at IETF wrote:
Hi, Stewart,

On Tue, Dec 4, 2018 at 6:07 AM Stewart Bryant
<stewart.bry...@gmail.com <mailto:stewart.bry...@gmail.com>> wrote:



     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
     <i...@kuehlewind.net <mailto:i...@kuehlewind.net>> wrote:

         Mirja Kühlewind has entered the following ballot position for
         draft-ietf-opsawg-ipfix-bgp-community-11: No Objection

         When responding, please keep the subject line intact and reply
         to all
         email addresses included in the To and CC lines. (Feel free to
         cut this
         introductory paragraph, however.)


         Please refer to
         https://www.ietf.org/iesg/statement/discuss-criteria.html
         for more information about IESG DISCUSS and COMMENT
positions.

         The document, along with other ballot positions, can be found
         here:

https://datatracker.ietf.org/doc/draft-ietf-opsawg-ipfix-bgp-communit
y/



         ----------------------------------------------------------------------
         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.


Yeah, that's where I was headed (stated more coherently).

Saying "I should do something, because the network path is STILL
congested" is safer than "I should do something because the network
path is congested", so now we're talking about suitable definitions of
"STILL". I was shooting for that with "persistent", and agree that
"permanent" path characteristics is a happy idea we aren't likely to
see in practice.

Do the right thing, of course ;-)

Spencer

     - Stewart

     Spencer



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