Subject: [tsv-area] Congestion Exposure (re-ECN): to BoF or to Bar BoF?

From: Bob Briscoe <[email-masked]>
Date: Thu, 21 May 2009 09:37:07 +0100

TSV Area folks,

[Please continue this discussion on tsvarea]

I'd like to launch a concrete protocol-specification activity on 
congestion exposure (with re-ECN as a candidate solution) in 
Stockholm? Here at the ICCRG in Tokyo, we've just agreed that this 
doesn't conflict with the new IRTF ICCRG  design team in this space 
or prejudge any consensus on direction (see background below). The 
question is purely about timing...

I'm finding that re-ECN seems to feature somewhere in the plans of 
those expressing an opinion in the ICCRG discussions. My concern: the 
protocol that will take longest needs to be finished soonest. E.g. 
ECN took 7 years from first research paper to proposed standard.

Therefore, I'd like to propose we get started on a specific protocol 
specification activity, in parallel to the ICCRG design team. We have 
to set this up so it doesn't imply it is the *official and only* way 
forward. But it's a good punt to be starting on.

My questions are:
* Do you think discussions should start on building a BoF on 
"Congestion Exposure" in Stockholm (getting late but still do-able)?
* Or less ambitiously should we arrange another ad hoc BoF (bar BoF) 
in Stockholm, building on ICCRG work in Tokyo this week, to get a 
community together to form a BoF later?
* Or do people actively oppose anyone doing anything yet on 
congestion exposure or re-ECN in the IETF or IRTF?

Background on TCP-unfriendly and on re-ECN
-------------------------------------------
You may be aware that, in San Francisco we had discussions in TSVArea 
(prompted by Matt Mathis's talk) on whether to move beyond 
TCP-friendliness as a comprehensive direction for both sharing 
Internet capacity and future congestion controls. In the IRTF ICCRG 
the same week it was decided to set up a design team to work on the 
way forward and propose it in an informational RFC - Matt Mathis has 
kicked off a first shot <draft-mathis-iccrg-unfriendly-00.txt>. We 
just had the launch meeting of that design team at the ICCRG here in Tokyo.

Re-ECN is a change to IP to make congestion as transparent to the 
network as it is to the endpoints (hence congestion exposure). Then:
i) causes of excessive congestion can be kept in check if ISPs choose 
- but at the bulk packet level like the Internet architecture should 
be - agnostic to behaviour of individual flows;
ii) and ISPs that under-provision can be held to account as well.
(see the end for the status of re-ECN).

Re-ECN status
-------------
We've been keeping a draft spinning on this proposed change to IP 
since 2005. It's still an individual contribution waiting for the right time.
<draft-briscoe-tsvwg-re-ecn-tcp-07>
<draft-briscoe-tsvwg-re-ecn-tcp-motivation-00>

When we first presented it and had subsequent ad hoc BoFs, the idea 
fell on stony ground. I think because back then few could see the 
limitations of TCP-friendly. Even if you still think there's 
something in TCP-friendly, it was apparent from the lack of any hum 
it received in SF that we at least need something wider.

It seems re-ECN is one of those things people want someone else to 
have already done. It gives a permit to be able to work on protocols 
that are really safe and fair, but they're not strictly TCP-friendly 
(e.g. mTCP, relentless, etc). For instance, re-ECN would allow ISPs 
to count how little congestion LEDBAT traffic was causing, so they 
need not count it against the user's allowance, etc.

We've now implemented it. There's now a great amount of security 
analysis on trying to game it and attack it and how it defends 
itself. People are working on using it as a basis for other DDoS 
protection mechanisms. Another is trying to build traffic engineering 
over it. Others are interested in deploying it using proxies. It's 
potential impact on net neutrality etc is being analysed by 
regulatory and economics people. So has it's time come?

Cheers

Bob

________________________________________________________________
Bob Briscoe,               Networks Research Centre, BT Research

---

From: "Carlberg, Kenneth G." <[email-masked]>
Date: Thu, 21 May 2009 11:42:46 -0400

Bob, 

<snip>
>  * Or less ambitiously should we arrange another ad hoc BoF 
>  (bar BoF) in Stockholm, building on ICCRG work in Tokyo this 
>  week, to get a community together to form a BoF later?

I'm certainly in favor of a discussion on building a BoF.  The worst
case scenario is that we find we still have a ways to go in defining a
charter and milestones and we simply have a bar-BoF in Stockholm to help
progress things.

>  You may be aware that, in San Francisco we had discussions 
>  in TSVArea (prompted by Matt Mathis's talk) on whether to 
>  move beyond TCP-friendliness as a comprehensive direction 
>  for both sharing Internet capacity and future congestion 
>  controls. In the IRTF ICCRG the same week it was decided to 
>  set up a design team to work on the way forward and propose 
>  it in an informational RFC - Matt Mathis has kicked off a 
>  first shot <draft-mathis-iccrg-unfriendly-00.txt>. We just 
>  had the launch meeting of that design team at the ICCRG here 
>  in Tokyo.

Just to be clear, was the outcome of the Tokyo meeting a conclusion that
re-ECN needs to be defined/standardized?  And if so, should we expect
other building block type of proposals from the ICCRG group, or is this
yet to be determined?  Or from this one foundation of a milestone (ie,
re-ECN), will only informational drafts be subsequently proposed in any
initial charter of the group? 

Cheers,

-ken

---

From: Bob Briscoe <[email-masked]>
Date: Tue, 26 May 2009 18:12:08 +0100

Dimitri,

I've cc'd to the iccrg, because it's a v good question that others on 
the list might want answered.

The discussions in Tokyo concluded that the ICCRG itself is mainly 
focused on congestion control protocols and there is less of an 
appetite for traffic security, policing etc. Therefore the ICCRG is a 
natural home for new congestion controls that might arise if 
congestion exposure existed, but not the best home to do the 
congestion exposure work itself.

Traffic security expertise is a fairly rare resource in the IETF/IRTF 
and it was thought they wouldn't feel ICCRG was their natural home.

Also, the proposal is for standards track, rather than IRTF activity 
on this particular aspect. This is because the research that has 
already been done has identified a piece that can safely and 
separately be standardised without committing to any particular 
transport behaviour that might be added on top.

Bob

At 11:00 23/05/2009, PAPADIMITRIOU Dimitri wrote:
>Bob:
>
>Why did you exlcude the possibility to progress the work in the ICCRG
>context ?
>
>Did you discuss this option/alternative in the context of the ICCRG
>meeting held in Tokyo ?
>
>thanks,
>-dimitri.
>
> > -----Original Message-----
> > From: [email-masked]
> > [mailto:[email-masked]] On Behalf Of Bob Briscoe
> > Sent: Thursday, May 21, 2009 10:37 AM
> > To: tsv-area IETF list
> > Cc: iccrg IRTF list
> > Subject: [tsv-area] Congestion Exposure (re-ECN): to BoF or
> > to Bar BoF?
> >
> > TSV Area folks,
> >

---

From: [email-masked]
Date: Tue, 26 May 2009 19:30:36 +0200 (CEST)

Hi,

I support this endeavor. I think it's a good idea.

Cheers,
Michael

---

From: <[email-masked]>
Date: Thu, 28 May 2009 10:27:46 +0100

Bob

I support this work. My views are that:

- work on Congestion Exposure (re-ECN) & TCP-unfriendly can proceed in
parallel - and in fact, given the time to get things done, the work
needs to be done in parallel. They're separate things - eg re-eCN
implies changes in network gateways, tcp-unfriendly could be useful in
some environments without re-ecn. (of course I'm not saying they're
completely independent - eg as you point out below their motivations are
connected.)
- on re-ecn, personally I don't see the benefit of waiting and would
prefer a BoF in Stockholm
- it would be good to see a proto-charter, or at least a list of
documents the WG would produce. Do you envisage the protocols being Expt
or Stds track? Is the output 1 protocol with similar scope to the
draft-briscoe-tsvwg-re-ecn-tcp, or are there more protocols? Plus what
other informational docs? - maybe some examples of how to use the
protocol - sort of an architecture doc?
- to me the point of the congestion exposure is that it's transparent in
2 senses: (1) it's visible to all network nodes (2) it's truthful. To
me, the reason re-ecn is very interesting is that it promises to give
both. I think both should be mentioned up front in any proto-charter as
what the objectives are.

Phil.

{ -----Original Message-----
{ From: [email-masked] [mailto:[email-masked]] On
{ Behalf Of Bob Briscoe
{ Sent: 21 May 2009 09:37
{ To: tsv-area IETF list
{ Cc: iccrg IRTF list
{ Subject: [tsv-area] Congestion Exposure (re-ECN): to BoF or to Bar
BoF?
{ 
{ TSV Area folks,
{ 
{ [Please continue this discussion on tsvarea]
{ 
{ I'd like to launch a concrete protocol-specification activity on
{ congestion exposure (with re-ECN as a candidate solution) in
{ Stockholm? Here at the ICCRG in Tokyo, we've just agreed that this
{ doesn't conflict with the new IRTF ICCRG  design team in this space
{ or prejudge any consensus on direction (see background below). The
{ question is purely about timing...
{ 
{ I'm finding that re-ECN seems to feature somewhere in the plans of
{ those expressing an opinion in the ICCRG discussions. My concern: the
{ protocol that will take longest needs to be finished soonest. E.g.
{ ECN took 7 years from first research paper to proposed standard.
{ 
{ Therefore, I'd like to propose we get started on a specific protocol
{ specification activity, in parallel to the ICCRG design team. We have
{ to set this up so it doesn't imply it is the *official and only* way
{ forward. But it's a good punt to be starting on.
{ 
{ My questions are:
{ * Do you think discussions should start on building a BoF on
{ "Congestion Exposure" in Stockholm (getting late but still do-able)?
{ * Or less ambitiously should we arrange another ad hoc BoF (bar BoF)
{ in Stockholm, building on ICCRG work in Tokyo this week, to get a
{ community together to form a BoF later?
{ * Or do people actively oppose anyone doing anything yet on
{ congestion exposure or re-ECN in the IETF or IRTF?
{ 
{ Background on TCP-unfriendly and on re-ECN
{ -------------------------------------------
{ You may be aware that, in San Francisco we had discussions in TSVArea
{ (prompted by Matt Mathis's talk) on whether to move beyond
{ TCP-friendliness as a comprehensive direction for both sharing
{ Internet capacity and future congestion controls. In the IRTF ICCRG
{ the same week it was decided to set up a design team to work on the
{ way forward and propose it in an informational RFC - Matt Mathis has
{ kicked off a first shot <draft-mathis-iccrg-unfriendly-00.txt>. We
{ just had the launch meeting of that design team at the ICCRG here in
{ Tokyo.
{ 
{ Re-ECN is a change to IP to make congestion as transparent to the
{ network as it is to the endpoints (hence congestion exposure). Then:
{ i) causes of excessive congestion can be kept in check if ISPs choose
{ - but at the bulk packet level like the Internet architecture should
{ be - agnostic to behaviour of individual flows;
{ ii) and ISPs that under-provision can be held to account as well.
{ (see the end for the status of re-ECN).
{ 
{ Re-ECN status
{ -------------
{ We've been keeping a draft spinning on this proposed change to IP
{ since 2005. It's still an individual contribution waiting for the
right
{ time.
{ <draft-briscoe-tsvwg-re-ecn-tcp-07>
{ <draft-briscoe-tsvwg-re-ecn-tcp-motivation-00>
{ 
{ When we first presented it and had subsequent ad hoc BoFs, the idea
{ fell on stony ground. I think because back then few could see the
{ limitations of TCP-friendly. Even if you still think there's
{ something in TCP-friendly, it was apparent from the lack of any hum
{ it received in SF that we at least need something wider.
{ 
{ It seems re-ECN is one of those things people want someone else to
{ have already done. It gives a permit to be able to work on protocols
{ that are really safe and fair, but they're not strictly TCP-friendly
{ (e.g. mTCP, relentless, etc). For instance, re-ECN would allow ISPs
{ to count how little congestion LEDBAT traffic was causing, so they
{ need not count it against the user's allowance, etc.
{ 
{ We've now implemented it. There's now a great amount of security
{ analysis on trying to game it and attack it and how it defends
{ itself. People are working on using it as a basis for other DDoS
{ protection mechanisms. Another is trying to build traffic engineering
{ over it. Others are interested in deploying it using proxies. It's
{ potential impact on net neutrality etc is being analysed by
{ regulatory and economics people. So has it's time come?
{ 
{ Cheers
{ 
{ 
{ Bob
{ 
{ 
{ 
{ ________________________________________________________________
{ Bob Briscoe,               Networks Research Centre, BT Research