Subject: [re-ECN] DRAFT minutes from the CONEX BoF at IETF76

From: Leslie Daigle <[email-masked]>
Date: Fri, 20 Nov 2009 17:25:30 -0500

Hi,

We had two note takers at last weeks meeting -- Steven Blake and Mat 
Ford.    Thanks, again, to both of them for their efforts.

Their notes are nicely complementary, so I've folded them together to 
provide a completer picture, and I propose them as the draft minutes 
from the meeting.  Review /comment from people who attended the meeting 
(f2f or virtually) would be appreciated.  (Steven & Mat -- feel free to 
shout out if you think I've (inadvertently) mangled your intent).

Leslie.

Congestion Exposure (CONEX) BoF
===============================
Tuesday, November 10 from 1520-1810

NOTES by Steven Blake, Mat Ford

CHAIRS:
	Leslie Daigle   <[email-masked]>
	Philip Eardley  <[email-masked]>

Meeting materials: https://datatracker.ietf.org/meeting/76/materials.html

AGENDA
------

Administrivia [ 5 mins]

- no objections to the agenda

Introduction by chairs [ 5 mins]

Background
   The problem [50 mins]

== End-user perspective [Murari Sridharan]

  - OS bottlenecks removed over last 6-7 years
  - congestion control has become so sophisticated they can fill up any 
residual capacity now
  - people complain about lack of resources now that pipes regularly get 
filled

to end-host, network is largely a black box - characteristics are inferred
imposes complex usage requirements - volume caps - example of end user 
hit with heavy pay-per-use bill for downloading windows update, despite 
the fact that windows update runs over a scavenger service.

network view - end hosts can't be trusted, application performance needs 
to be inferred, end-hosts typically establish connectivity to well-known 
servers, but reality is different.

innovation is all in layer-violation - this isn't sustainable!

congestion control purity is no longer reality - TCP tunnelled inside 
TCP isn't a route to deterministic results!

- no comments at the mic

== ISP Context/motivation [Rich Woundy]

Enable customers to control their own network experience - take ISP out 
of the loop of being 'congestion police'

 > Linda Dunbar: you discuss making the heavy user lower priority; what does
   this have to do with network congestion?

 > Rich W: Comcast mechanism is not a conex proposal.  Our mechanism 
does not
   see end2end.  It only solves congestion problem at the edge, not for 
any other part of our network or for third parties. comcast solution is 
monitoring capacity and resource use in the network. Measuring 
end-to-end congestion requires another mechanism.

 > Linda Dunbar: congestion is very transient.  End user has no control over
   over the network's behavior.

 > Leslie: wait until after the other presentations

 > Bob Briscoe: mention LEDBAT

 > Leslie: non-IETF ISOC meeting today on bandwidth; meeting materials
   (including audio) at ISOC website

== Technical problem [Mark Handley]

whenever he presents about congestion people say 'we're overprovisioned, 
don't care' - he doesn't subscribe to that - will talk about why we need 
to care about congestion

TCP isn't broken, but we can do better

used to be receive window limited in end systems - no longer the case in 
popular modern TCP stacks

goal should be for congested networks, at least at the bottleneck

packet loss isn't necessarily a problem - for apps where it is a problem 
we have ECN

 > Greg Lebovitz: think about next-gen apps, and where they might
   fit on the latency/size graph (e.g., Internet-of=things).  Existing apps
   were built a certain way because the network works the way it does.

 > Mark H: some things we haven't put on the net because they don't work 
with
   today's Internet.

 > Geoff Huston: making a good use of the network in either case (re: 
latency,
   latency, latency) slide.

 > Mark H: better from a user's perspective

 > Aaron Falk: ISPs aren't charging by the byte

 > Jana Iyengar: works at residential education institution - students 
tend to do a lot of 'stuff' that needs separated from academic work - 
DPI is used for that, maybe in other enterprises too

 > Ben Niven-Jenkins: if the prime driver for ISPs to use DPI is to control
   costs, don't see how it is relevant in the context of controlling
   congestion

 > Mark H:  because they need to control costs, because they have 
congestion - need to maintain good service for higher-paying customers; 
trying to provide acceptable service to non P2P apps.

 > Ben N-J: DPI being used to prevent going over usage caps

 > Mat Ford: That doesn't explain why users on relatively low service 
tiers have their throughput throttled regardless of whether or not they 
have exceeded any volume threshold

 > Ben N-J: economic issue; how does technology solve it.  Don't know 
how the
   two are linked.

 > Vijay Gill: agree with Mat; if an ISP have chronic congestion, why not
   keep raising the price until users fall off.  Comcast has two tiers of
   service (residential, business).  Residential has 250 GB cap; business
   service has no cap.  Most folks I know go for the business service
   ($100/month).

 > Bob Briscoe: try to answer Ben's question - he was talking about 
retail ISPs
   as customers.  Wholesaler sells bit rates to the retail ISPs.

 > Ben N-J: it is not us causing the bottlenect

 > Leslie: not here to talk about how to make things work with DPI; 
let's move
   on.

 > Stanislav Shalunov: what can you convey with conex that you can't 
convey with
   simple drops?  Latency ...

 > Mark H: only talking about the problem space

 > Stanislav S: current loss rates (< 1%) are working fine.

 > Mark H: loss rates are very variable

 > Aaron Falk: re: IETF Goals - we shouldn't be talking about economics.
   Disagree that the only cost is congestion cost (overstatement).
   Infrastructure has cost.  Question is incremental cost.  Economic 
expertise
   would be useful in this discussion.

 > Mark H: yes, underutilised network gives you ability to communicate - 
additional traffic doesn't cost anything more, until you experience 
congestion

   Towards a solution [20 mins]

== Overview of re-ECN   [Bob Briscoe]

 > Greg L: before when we saw that sometimes there is a long duration 
connection
   and something that was very short has to wait, in that case, one of them
   will show the network is very bad, and the other one showing that the
   network is very working well.

 > Bob B: small transfer can go fast, because it won't build up a big
   congestion volume; incentive for large transfer to back off because 
it could
   build up large congestion volume.

 > Greg L: how do they know about each other?

 > Bob B: because of the congestion notifications.  I'm able to use up my
   congestion allowance if I know I won't be transferring long.

 > Greg L: you said that is how TCP works.  This works by some box in the
   middle.

 > Bob B: imagine a TCP with either a high weight or a low weight.

 > Greg L: is it dependent on a box in the middle, or just the endpoints.

 > Bob B: box in middle just enforces congestion volume allowance, in one
   possible deployment.

 > Lars Eggert: trying to show that the problem is solvable, not that this
   is the solution.

 > Lars Eggert: we believe you Bob that you can't cheat (leap of faith)

 > Murari S: Thought I understood conex, not I'm confused.  If you only look
   at the problem of short flows coming in and using lots of BW, problem
   can be solved if all the bulk users used scavenger service.  Problem 
would
   automatically solve itself.

 > Bob B: ISPs can't see congestion, how do you get a free pass.

 > Murari S: ISPs problem is because customers complain that they're not
   getting service.

 > Philip E: ISPs can't trust that end users are using LEDBAT; don't 
want them
   using DPI to figure this out.  Trying to get the two to cooperate.

 > Murari S: if everyone would start using scavenger, then the main purpose
   of Conex is to reroute traffic under congestion.

 > Bob B: how does the ISP know that the user is using LEDBAT. Purpose 
is to help operators know which traffic is causing most congestion

 > Mark H: reasonable for ISPs to limit traffic that is causing a problem.
   But ISPs cannot see which traffic is causing the problem.

 > Jana Iyengar: incentive issue with LEDBAT; end hosts may choose not to
   use it.

 > Bob B: what about big-big flows and little-big flows?  Two classes 
may not
   be enough.

 > Stanislav Shalunov: why send the info the user?  Why not keep it within
   the ISP, so that you can evolve the algorithm.

 > Bob B: don't want to do congestion control within the network.

 > Stanislav S: seems like two justifications: solve the LEDBAT problem, ??

 > Lars Eggert: bunch of questions, high-level question is whether we all
   understand what the problem is, seems like it.  Questions that relate
   to whether exposing congestion solves the problems.  Then questions 
around
   how re-ECN exposes congestion.

 > Leslie: next discussion is around principles and constraints.

 > Lars Eggert: should have questions along whether there is a problem that
   IETF should solve.  Is everyone confused? Then there is a question of 
whether exposing congestion is a way to solve the problem, then there is 
the question of re-ECN as a suitable solution - lets tease these apart, 
and start at the beginning

 > Linda Dunbar: want to confirm the problem statement, to expose network
   congestion to the end user?

 > Bob B: the opposite - expose it to the network

 > Linda Dunbar: if I'm an end user, what benefits me by doing something
   different?

 > Bob B: suppose I say that the amount of volume you send is a problem;
   that's not true.  I can't judge whether you are sending during a trough.

 > Linda D: one application is so trivial in the whole network.

 > Leslie: hypothetical, my husband tells me the road is congested; I can
   use the toll road or wait in traffic

 > Linda D: I don't have a choice

 > Bob B: you can choose to slow down and send later

 > Linda D: can we have one single problem statement?

 > Aaron Falk: minor epiphany - way to identify responsive flows; give them
   a seal of approval, giving them higher priority.  Been discussed in IETF
   for a long time.  However, you are talking about aggregated statistics,
   idea of distinguishing flows is problematic.

 > Bob B: can differentiate between networks that encourage users to behave
   vs. ones that don't.

 > Tim Shephard: answer Lars - I think I understand this, but it has nothing
   to do with what I have heard in this room today.  Seen Bob talk many 
times
   and I don't think he has taken people that don't understand this to
   understand it.  Not effective use of time to get these people to 
understand
   this in the meeting.  You want to expose to your ISP which traffic you
   are sending is exposing congestion somewhere in the network.  ISP has 
another
   thing to bill you on.  ISP than then stop billing you on how much total
   traffic you send, so then you can send lots of traffic.  It might be
   possible, bit of genius here.  Whether IETF should proceed is the 
question
   here.  will waste time if we try to educate everyone today.

 > Leslie: line closed after Stanislav

 > Luca Martini: talking about congestion-based pricing.  What is the 
guarantee
   I have as a user that the network will provide enough BW?

 > Bob B: ISP wants to try to offer a better service than other ISPs.  If it
   is only limiting the traffic that causes congestion, you can get more out
   of my network.  If I allow my network to get more congested I'd have 
a crap network and would lose customers. Overall bandwidth availability 
isn't the issue, it's about good use of the available capacity - doesn't 
mean net-ops can ignore need to provision 'adequately'.

 > Luca Martini: what is the SLA that you are giving me?

 > Bob B: my SLA might be that you can send 70 GB a day under typical 
conditions

 > Rich W: not sure I am changing my pricing as a result of this

 > Matt Mathis: very worried that there is a bigger problem on the horizon
   that conex might be part of the solution.  TCP Friendly is an 
oxymoron, only
   beginning to feel the symptoms of that.

 > Murari S: brilliant extension of ECN, summarizing: causes better 
cooperation
   between users so we don't have to do wierd things in the network, 
incentive
   to use scavenger service, better traffic engineering in the network

 > Christian Vogt: presentations show that the is an improvement 
opportunity.
   ECN has not been deployed.   Seems like this is a solution to congestion.
   Would this be more likely to be deployed than ECN?  Why is it easier to
   deploy than ECN.  Think it might be due to additional incentives.

 > Bob B: why is this more deployable?  Would give network operators much
   better incremental performance boost than just with ECN.  It would 
give net-ops a stronger incentive to get much greater performance out of 
their network

 > Stanislav S: made the point that ISPs cannot trust users to use the
   right applications.  If this does affect pricing, this is a license to
   charge whatever you want, because the network is sending you the signal
   that you are congested.

 > Leslie: this is about information available in the network

 > Stanislav S: don't see incentives to setting those markings in 
congestion.
   Only works with perfect competition and transparency.  If there is no
   pricing impact, then this is an extra throttle (?).  Applicable to any
   mechanism ...

 > Lars Eggert: this isn't the network telling the end system that there 
is congestion - ISPs can already drop packets if they don't like your 
flow. The question is can the ISP correctly trust the end-systems to 
accurately indicate the congestion that they are going to cause.

 > Stanislav S: extra throttle, it already has a throttle because it can 
drop
   packets.

 > Philip E: several points. ISPs can't lie to their end-users in the 
presence of competition and negative customer feedback. In a market 
where you have a termination monopoly, they can charge what they like 
anyway, so this doesn't make a difference - that problem can only be 
solved through regulation.

 > Jana Iyengar: re-ECN presentation conflated two things: one way to expose
   congestion, and what the operator could do with the information.  That
   is one candidate way of exposing congestion.

 > Leslie: moving discussion to whether there is a problem for the IETF to
   solve.

 > Lars Eggert: knew that this wasn't an easy thing to get your head around.
   Who has read the documents? (several hands).  Who thought that the 
documents
   were perfectly clear? (didn't check for hands).  Expected more discussion
   on the mailing list.  Disappointed.  Not sure if we are ready at this 
point
   to discuss a charter.  Problem statement is good to discuss now.  If we
   are going for a second BoF, shouldn't spend time on tutorials.

 > Matt Mathis: how much risk there is associated with starting the work 
before
   everything else is clear.  Launch with a draft charter.

 > Bob B: one way to ask the question is whether those who don't 
understand it
   from stopping those that do from solving it.

 > Leslie: for those who do understand it, is the problem statement 
something
   the IETF should undertake (lots of hands), if you believe the IETF should
   not undertake (no hands).

 > Greg L: process point, reason we bring to standards is so that everyone
   else can understand and implement.  Need to make sure that the rest of
   the community can understand.

 > Matt Mathis: to people who don't understand it; how many of them are 
afraid
   of it.

 > Stanislav S: believe I understand, but my understanding does not 
correspond
   with the intended one.

 > Leslie: repeat with hums
   - understand the material, believe the problem statement describes work
     the IETF should do (loud hum)
   - understand, don't believe this is a good problem statement (silent)
   Believe there is momentum

 > Mat Ford: another 30 minutes left, good use of remaing time to explain
   for those who don't understand

 > Jana I: we need a really well written applicability statement

 > Aaron Falk: problem statement doesn't say anything about whether this is
   a standards activity; is that the intention

 > Philip E: deliberately did not answer that in the charter; let IESG 
decide
   that.

 > Aaron Falk: good candidate for experimental/informational RFCs on 
possibly
   multiple mechanisms; premature for standards track.

 > Vijay Gill: very interesting work; should proceed; need deployment
   considerations documentation

 > Leslie: two things: deployment considerations, how this would be 
considered
   useful in practice

 > Alissa Cooper: tried hard to keep the potential uses apart from what is
   being exposed, but it makes it more difficult to understand why this is
   useful without describing assumptions about ISP business models.

 > Leslie: important output would be an applicability statement

 > Francois Le Faucheur: responding to Stanislav - if ISPs don't make use of
   the feedback in unpleasant ways, then it is not useful, may be true.
   Good properties because it is incrementally deployable.  Not obvious that
   this won't work.   There is space for someone to say "in my resterant, if
   you eat more, you pay more"

 > Ingemar Johansson: don't want to exclude other transports than TCP.
   Feels that different dynamics in congestion behaviour could cause 
some issues for a protocol like this.

 > Stanislav S: difference between restaurants and data transmission is 
ratio of cost of billing to cost of goods. Restaurants will itemise, but 
in data networks models are simpler.

 > Bob B: reason I put up congestion volume bill, was because it is simple.

 > Francois L: agree?

 > Stanislav S: ISPs will expose congestion, but sometimes you will get to
   send more, sometimes less. I expect that ISPs would use flat-pricing 
but impose different congestion limits.

 > Francois L: something better than flat rate will evolve.  Like saying
   unlimited calling for cell phones.

 > Stanislav S: that is how things are rapidly evolving

 > Leslie: should a WG be formed with this charter + some word-smithing
   - Yes (some hums)
   - No  (some hums)
   Seems that there is rough consensus to form a WG.  Willing to declare 
victory.

 > Philip E: demo will start in 5 minutes.

Meeting adjourned.

Agenda items not formally not addressed:

Discussion of potential IETF work
   Constraints [10 mins] [Philip Eardley]
   Discussion of viability of congestion exposure [40 mins] [Leslie Daigle]
   Draft charter discussion [20 mins]

-- 

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"Reality:
      Yours to discover."
                                 -- ThinkingCat
Leslie Daigle
[email-masked]
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