Re: [Codel] sprout

[Jim Gettys <jg@freedesktop.org>]

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Keith,


On Wed, Jul 10, 2013 at 4:19 PM, Keith Winstein <keithw@mit.edu> wrote:

> Thank, Dave.
>
> We have a Web site with more info, a talk, and source code (
> http://alfalfa.mit.edu) if anybody is interested.
>
> Something that may interest folks here is that we compared
> Sprout-over-unlimited-buffer with TCP-Cubic-over-CoDel on these
> cellular-type links. That is, a scenario where the network operators
> implemented CoDel inside the LTE/UMTS/1xEV-DO base station (for the
> downlink) and the phone manufacturers implemented CoDel inside the
> "baseband" chip for the uplink.
>
> Bottom line results is that for the case where a cellular user can control
> all their own flows, it's roughly a wash. To a first approximation, you can
> fix bufferbloat on a cellular network *either* by putting CoDel inside the
> base station and baseband chip (and otherwise running the same endpoint
> TCP), *or* by changing the endpoints but leaving the base station and
> baseband chip unmodified.
>

Did you compare with fq_codel?  None of us (Van included) advocate CoDel by
itself.


>
> Obviously we benefit dramatically from the per-user queues of the cellular
> network. By contrast, in a typical house with a bufferbloated cable modem
> where one user can cause big delays for everybody else, you can't fix
> bufferbloat by fixing just one endpoint. We will have some results soon on
> whether you can fix it by fixing all the endpoints (but still leaving the
> "bloated" gateway intact).
>

Yup, per user queues help.  But those per-user queues can be extremely
large; you can hurt yourself as soon as you want to mix your WebRTC kind of
traffic with anything else.

Jim


>
> Cheers,
> Keith
>
> On Wed, Jul 10, 2013 at 3:30 PM, Dave Taht <dave.taht@gmail.com> wrote:
>
>> I haven't been paying a lot of attention to rmcat and webrtc until
>> recently, although I'd had a nice discussion with keith on it a while
>> back..
>>
>> this particular thread sums up some interesting issues on that front.
>>
>> http://www.ietf.org/mail-archive/web/rmcat/current/msg00390.html
>>
>> --
>> Dave Täht
>>
>> Fixing bufferbloat with cerowrt:
>> http://www.teklibre.com/cerowrt/subscribe.html
>>
>
>
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>
>

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