From: Michael Richardson <mcr@sandelman.ca>
To: dpreed@reed.com
Cc: cerowrt-users@lists.bufferbloat.net, cerowrt-devel@lists.bufferbloat.net
Subject: Re: [Cerowrt-devel] [Cerowrt-users] QOS settings vs speedboost and random bandwidth
Date: Mon, 26 Nov 2012 10:38:33 -0500 [thread overview]
Message-ID: <13866.1353944313@obiwan.sandelman.ca> (raw)
In-Reply-To: <1353942251.571510886@apps.rackspace.com>
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>>>>> "dpreed" == dpreed <dpreed@reed.com> writes:
dpreed> You can use a small fraction of the capacity of the cable
dpreed> uplink path to measure its queueing delay dynamically, and
dpreed> when it gets longer than latency*"expected bitrate", reduce
dpreed> "expected bitrate".
dpreed> You want to do this *as quickly as possible*, so what you do
dpreed> is insert a "link monitor" task in the driver that sends
dpreed> tiny probe packets addressed to the nearest "loopback point"
dpreed> you can find/create on the other side, and measure the RTT.
dpreed> You can use, for example, the technique used by traceroute,
dpreed> which is to set the hop count to the smallest number that
dpreed> causes a return ICMP packet to be sent, and send one of
dpreed> those periodically.
As I understand it, you can do this with 802.1ag
http://en.wikipedia.org/wiki/IEEE_802.1ag,
with the Loop-back frames as well.
Whether or not any of this is enabled on typical broadband networks, I
have no idea.
dpreed> I used this specific technique to cause my uplink queue to
dpreed> move back into my router, where I could manage it. You can
dpreed> also use it for the downlink queue measurement, but it
dpreed> doesn't move the queue into the router smoothly, instead you
dpreed> have to drop/ECN-mark the IP frames coming in.
dpreed> This can all be done between the IP layer and layer 2.
dpreed> Since it exploits speedboost better, it might be worth
dpreed> adding as an option to cerowrt, so you don't have to set a
dpreed> speed limit explicitly when you have a single connection to
dpreed> the public Internet.
wow, this would be awesome... code??
--
] He who is tired of Weird Al is tired of life! | firewalls [
] Michael Richardson, Sandelman Software Works, Ottawa, ON |net architect[
] mcr@sandelman.ottawa.on.ca http://www.sandelman.ottawa.on.ca/ |device driver[
Kyoto Plus: watch the video <http://www.youtube.com/watch?v=kzx1ycLXQSE>
then sign the petition.
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next prev parent reply other threads:[~2012-11-26 15:38 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20121125232034.GF24680@merlins.org>
2012-11-26 8:32 ` Dave Taht
2012-11-26 14:22 ` Michael Richardson
2012-11-26 15:04 ` dpreed
2012-11-26 15:38 ` Michael Richardson [this message]
2012-11-26 16:37 ` dpreed
2012-11-26 18:11 ` Michael Richardson
2012-11-26 19:23 ` Marc MERLIN
2012-11-26 19:58 ` dpreed
2012-11-26 21:27 ` Michael Richardson
2012-11-26 22:26 ` dpreed
2012-11-26 15:35 ` Jim Gettys
2012-11-26 18:13 ` Michael Richardson
2012-11-26 18:28 ` Jim Gettys
2012-11-26 21:29 ` Michael Richardson
2012-11-26 15:27 ` Jim Gettys
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