From: Andy Furniss <adf.lists@gmail.com>
To: Jonathan Morton <chromatix99@gmail.com>
Cc: Cake@lists.bufferbloat.net
Subject: Re: [Cake] low bandwidth default params best effort vs voice latency.
Date: Sun, 5 Mar 2017 12:37:38 +0000 [thread overview]
Message-ID: <325f92c7-e867-6511-f5c9-8f1f6f6abe2f@gmail.com> (raw)
In-Reply-To: <95D56BA5-0C5E-4D2E-B28F-A8C957B5F65D@gmail.com>
Jonathan Morton wrote:
> Okay, I think I’ve worked out what is happening.
>
> At 250KB/s, it takes 6ms to get one 1500-byte bulk packet down the
> pipe. This is unavoidable, so having a bulk flow competing with your
> game traffic will always increase your peak latency by that much.
>
> With three independent game streams in play, it’s possible for them
> all to transmit simultaneously *and* to coincide with a bulk packet
> having just been sent. With overheads, it will take a total of 8.5ms
> to get all four packets through. This corresponds nicely to your
> best-effort results; you’re getting very close to the theoretical
> best performance there.
Yea, the pleasures of low bandwidth - not that I would have called 2mbit
low a few years ago, and 8ms isn't that bad.
Historically, I once had an asymmetric mss clamping setup so up tcp
was smaller than down.
> So Diffserv marking actually can’t improve your performance in this
> particular case. But it shouldn’t make it worse either. You’re
> actually seeing a nearly 6ms increase in peak latency, which
> corresponds neatly to an additional bulk packet ending up ahead of
> the game traffic in the queue.
>
> That’s not supposed to happen, but I think I can see how it *can*
> happen with the current Diffserv logic. It’s a weighted DRR, much
> like what is used between flow queues a little further down - but it
> *doesn’t* have a special bonus for sparse tins. That’s something I
> clearly need to fix.
>
> To help remind me, please do open an issue on the Github project.
OK, I opened
https://github.com/dtaht/sch_cake/issues/52
prev parent reply other threads:[~2017-03-05 12:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-04 18:21 Andy Furniss
2017-03-04 18:45 ` Jonathan Morton
2017-03-04 19:28 ` Andy Furniss
2017-03-04 20:27 ` Jonathan Morton
2017-03-04 23:05 ` Dave Taht
2017-03-05 12:43 ` Andy Furniss
2017-03-05 12:37 ` Andy Furniss [this message]
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