[Bloat] What is fairness, anyway? was: Re: finally... winning on wired!

[Jim Gettys]

On 01/02/2012 04:31 PM, Dave Taht wrote:
> On Mon, Jan 2, 2012 at 9:07 AM, Dave Taht <dave.taht at gmail.com> wrote:
> Yes, that patch brings SFQ at light workloads to being
> indistinguishable from QFQ!
> http://www.teklibre.com/~d/bloat/sfqnewvsqfq10iperfs.png (if you stare
> at this image long enough you might see a pattern, but I don't) (I
> certainly am seeing an afterimage, though)
>>> A "nolimit" implementation could use a dynamic memory allocator
>>> scheme, eventually consuming less memory on typical use :)
> At what point could SFQ be considered a replacement for pfifo_fast? :)
>
> I have not managed to crash QFQ yet with your other new patch. I will
> run it overnight.
>
>

As I read this thread, there are three questions that go through my mind:
    1) since TCP is not "fair", particularly when given flows of
different RTT's, how do we best deal with this issue?  Do either/both
SFQ/QFQ deal with this problem, and how do they differ?
    2) Web browsers are doing "unfair" things at the moment
(unless/until HTTP/1.1 pipelining and/or SPDY deploys), by opening many
TCP connections at the same time.  So it's easy for there to be a bunch
of flows by the same user.  Is "fairness" better a per host property in
the home environment, or a per TCP flow?  Particularly if we someday
start diffserv marking traffic, I suspect per host is more "fair", at
least for unmarked traffic.
    3) since game manufacturers have noted the diffserv marking in
PFIFO-FAST, what do these queuing disciplines currently do?
                    - Jim