[Bloat] [iccrg] ECN issues

Sun Jul 19 04:21:12 EDT 2015

Hi Ingemar,

I was to make that very same point; from my earlier collaboration with Mirja and Brians efforts, I think the prevalence of gear that still uses a notion of a TOS byte, and rewrites it for a L4 flow is actually higher than ECN impacting connection set up etc.

So, on some paths you may believe you negotiate ECN, but one half-link may bleach the IP-header ECN bits.

Again, this is detectable for the receiver (currently, no mechanism to convey this info back to a TCP sender), and affected sessions would revert back to loss-based CC.

Such ECN-unresponsive, loss-responsive flows may pose an issue to AQMs that do some differentiated handling of ECN vs non-ECN packets though...

Best regards,
  Richard

> -----Original Message-----
> From: iccrg [mailto:iccrg-bounces at irtf.org] On Behalf Of Mirja Kühlewind
> Sent: Montag, 29. Juni 2015 14:56
> To: Ingemar Johansson S
> Cc: cheshire at apple.com; iccrg at irtf.org; Dave Taht (dave.taht at gmail.com);
> Bob Briscoe (bob.briscoe at bt.com); bloat at lists.bufferbloat.net;
> ietf at trammell.ch
> Subject: Re: [iccrg] ECN issues
> 
> Hi Ingemar,
> 
> we did only test connection setup up and some small transmissions so far.
> We did not measurement anything with longer connection though. However,
> from these results I'd also say there are no mayor issues anymore. There
> are still some boxes that overwrite the IP ECN bits because they still
> think it's part of the ToS field. However, those cases are rather easy to
> detect because all packets should have the same marking. Linux implements
> an easy fallback where ECN is disabled if the SYN is ECN marked. That's
> probably not the perfect solution but mostly helps the problem.
> 
> Mirja
> 
> 
> > Am 25.06.2015 um 21:02 schrieb Ingemar Johansson S
> <ingemar.s.johansson at ericsson.com>:
> >
> > Hi
> >
> > And thanks all for the info both on and off list. I believe that I have
> enough information. The main objective for me was to get an understanding
> how serious the issues that various boxes in the middle (e.g NATs/FWs )
> mess with the ECN bits really is. Seems to me, based on the info I
> received thus far that this is becoming more and more an non-issue ?.
> >
> > Realized that I have seen the below paper before,  somehow I mixed it
> > up with the older paper, have to blame it on my own teflon-memory ...
> > Thanks for refreshing my memory
> >
> > /Ingemar
> >
> >> -----Original Message-----
> >> From: Mirja Kühlewind [mailto:mirja.kuehlewind at tik.ee.ethz.ch]
> >> Sent: den 25 juni 2015 19:31
> >> To: Ingemar Johansson S
> >> Cc: bloat at lists.bufferbloat.net; iccrg at irtf.org; Bob Briscoe
> >> (bob.briscoe at bt.com); ietf at trammell.ch; Dave Taht
> >> (dave.taht at gmail.com); cheshire at apple.com
> >> Subject: Re: ECN issues
> >>
> >> Hi Ingemar,
> >>
> >> there is a newer paper we published last year (and gave a quick
> >> presentation at the last ICCRG meeting):
> >>
> >> http://wan.poly.edu/pam2015/papers/4.pdf
> >>
> >> https://www.ietf.org/proceedings/92/slides/slides-92-iccrg-1.pdf
> >>
> >> In the mean time we did more measurements using BitTorrent clients
> >> instead. The results are very similar. We might be able to quickly
> >> present some new results at the next session (if the session takes
> >> place and there is still space).
> >>
> >> Does this help or are you looking for some specific information?
> >>
> >> Mirja
> >>
> >>
> >>> Am 24.06.2015 um 13:34 schrieb Ingemar Johansson S
> >> <ingemar.s.johansson at ericsson.com>:
> >>>
> >>> Hi
> >>>
> >>> I wonder, is there any new data around that gives any ideas how
> >>> large the
> >> issues with ECN really are ?.
> >>>
> >>> Issues that I am interested are ECN black holes and faulty remarking
> >>> of ECN fields
> >>>
> >>> The last one I have seen is this paper by Mirja, Brian and Sebastian
> >>> Neuner
> >>> http://www.ict-mplane.eu/sites/default/files/public/publications/311
> >>> ec
> >>> ndeployment.pdf
> >>>
> >>> Is there any new data available ?.
> >>>
> >>> /Ingemar
> >>> =================================
> >>> Ingemar Johansson  M.Sc.
> >>> Senior Researcher
> >>>
> >>> Ericsson AB
> >>> Wireless Access Networks
> >>> Labratoriegränd 11
> >>> 971 28, Luleå, Sweden
> >>> Phone +46-1071 43042
> >>> SMS/MMS +46-73 078 3289
> >>> ingemar.s.johansson at ericsson.com
> >>> www.ericsson.com
> >>>
> >>> "No man has a good enough memory
> >>>  to be a successful liar"
> >>>    Abraham Lincoln
> >>> =================================
> 
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